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This thread originated from one started by Gordo so you can find the background there. However, I've copied and edited two of my posts from there to start the present thread.

I looked into engine simulation software in some detail to try to find the "best" one for simulating Gold Star engine performance. The good news is there are a lot of choices (including Engine Analyzer, Desktop Dyno (also versions called DynoSim and DynoMation), Engine Pro, GT-Power and Virtual Engine Dyno, and probably others). The bad news, is, there are a lot of choices.

It seems there are three price points, ~$100, ~$200 and ~$500 for three levels of capabilities. Unfortunately, comparing those capabilities is problematic. The manuals available for download for two of these are 323 and 314 pages, which would be a lot of material to have to read in detail to compare just those two programs. It's quite possible one program could have more capabilities than another but be missing some useful feature that the other has. Further, since there are no downloadable manuals for the other programs, all there is for them are one or two-page descriptions on the web.

OK, given the impracticality of determining the "best" simulation program, I returned to my initial thought of 'Engine Analyzer Plus' by Performance Trends. I've used two generations of their 'Port Flow Analyzer' with my flow bench and have been happy with the software and with their responsiveness in providing me with new software keys when I migrated to new computers every few years. Also, the company has been around since 1986 and their engine software has gone through a number of upgrades since then. Given this, I went through two rounds of questions with their support line and they satisfactorily answered my questions about the capabilities of 'Engine Analyzer Plus' for present purposes:

--------------------
For any accurate simulation, accurate head flow data is critical. However, there are some generic head and intake and exhaust examples for you to pick from, inside all our Engine Analyzer programs

Predicting changes in burn rate (which determines spark advance) is not something the Plus version deals with in great detail. Still, it WILL give you an estimate of a safe spark curve for different combos of engine parts with different octane fuels.

It is used mostly to predict the different torque and HP curves for these modifications.

-----------------------

Translating the above, the first paragraph answers my question about whether the program has generic head options. It does, so this will let me use BSA's h.p. and torque vs. rpm curves to pick a generic head that reproduces the data, rather than having to input actual flow data on each head.

The second paragraph answers my question about fuels. Basically, it says that while it might estimate, say, 36-deg. for the spark advance for the stock configuration of my Competition (for which BSA says 39-deg.), it might then give a different estimate if I input a different CR. If that new figure were, say, 34-deg., that would indicate less advance would be needed with the new CR. While I couldn't necessarily rely on either value as being accurate, the relative difference would be useful information.

The third paragraph is the reason for doing this in the first place. Once the parameters fit the BSA curves for a given stock configuration, the effect of changing CR, cams, etc. on the engine performance will be determined. Instead of "I think the xx-xxxx inlet cam feels like it has more mid-range power," it will be clear whether or not it actually does.
I think I've caught and corrected all of my mistakes and now have reasonable input parameters for everything needed by 'Engine Analyzer Plus' (although at this point I'm continuing to work on those parameters). For example, a few weeks ago I measured the flow of my 1½" GP to be 85.1 CFM @ 3" H20. However, the simulation program uses what it says is the industry standard test condition, which is 1.5" Hg. The Superflow manual gives 2.58x as the factor to use to convert, giving 219.6 CFM @ 1.5" Hg, so that's what I entered into the program.

Another example is p. 22 of 'Goldie' shows cross sections of the ports of 350 cc heads. Scaling the 1956 drawing to the 1-5/32" ID of the port, the length is ~4.6". Although that length is for a 350 cc DB head, it should be essentially the same for a DBD. In any case, that's what I used.

As long as I didn't make any mistake with converting the cam specs to the way the program needs them as inputs this simulation program still leaves the exhaust system as an uncertainty. BSA gives data for 5000-7000 rpm for the Clubman DBD so nothing below 5000 rpm is available to "calibrate" the simulation program. Despite that, I started the simulation at 3200 rpm in the attached graph to show the effect of the exhaust system. Keeping the total length about the same but changing the details can easily move the dip centered at ~3000 rpm in this graph up to ~5000 rpm. Although the simulation has an input for straight pipes, so Scramblers and Catalinas can be modeled with more certainty, silencers or megaphones of any type, including 'twitter' silencers, will be an issue since the dyno data doesn't cover the lower rpm region where the silencers have an effect.

With that background, the fact this initial simulation underestimated the h.p. of this DBD by ~7% is irrelevant. The important thing about this graph is how well it parallels the actual dyno data. First, the program's manufacturer only claims +/-7% agreement with actual measured dyno data. And second, I haven't necessarily found the final "best" set of input parameters so the graphs in this post should be regarded as "preliminary tests" at this point.

As an observation, it's been quite informative to work with the program. To avoid clutter I ran the "final" simulation twice so that the attached graph only would have one set of h.p. and torque curves. When working with the program, though, you can change a parameter, run the simulation, and the graph shows the latest result along with the previous one. This makes it very easy to learn what changes have what effects, and where those effects are in rpm.

As an example of what this simulation program makes possible, the second graph shows the calculated consequences of switching from a 1½" GP to a 1036 Concentric with a K&N filter on it. All other parameters of the simulation were kept constant and only the carburetor CFM was changed from 220 to 179 to correspond to my recent flow bench measurements.

Although the Concentric with filter flows 18% less air than the straight-through GP the simulation says using it only would knock ~2% off the maximum h.p. Personally, I was willing to give up even more h.p. than this not to have to deal with a GP, but I was pleasantly surprised to find there will be only a relatively trivial loss.

After taking time to check for the Nth time that I've correctly converted the data for the 65-2442 and 65-2446 cams I'll start converting the other relevant ones. I'll also continue checking to be sure all the other input parameters I've used are reasonable since, once I'm confident in them, knowing the parameters that work for the DBD Clubman should make it faster to set up simulations for other Gold Star models back through the ZB.


Attached picture EngineAnalyzer_DBDClubman_Test01.jpg
Attached picture EngineAnalyzer_DBDClubman_Test02.jpg
MM: Let the fun begin! I have the cams and pistons lined up on the bench awaiting the data that will give me the best possible engines for today's conditions.

Gordo
Heres my friends Goldie, stats.
Pearson motor.
Capacity 604 cc
Bore 90 mm
Stroke 95 mm
CR 9:1
Inlet cam 65-2442
Exhaust cam 65-2446
Carb 1 1/2 GP 3GP needle, NJ 109, MJ 350 Cutaway 4, std air stack Bell mouth.

Timing 39 degrees BTDC

Max RPMs 6,500.
Clubmans type exhaust.
STD DBD 500 head/ valves.

What else do you need by the way of info?. From the above would it be possible to investigate what different ignition timing would do?.
edited , cam nos changed.
Originally Posted by gavin eisler
would it be possible to investigate what different ignition timing would do?.
Unfortunately, as the support staff warned me ahead of time, the 'Plus' version is limited in what it has to say about timing and knock. For that the $500 'Pro' version is needed.
----------------------------
'Plus'
Program sets spark to produce best power. Program also predicts when knock occurs and will reduce spark advance (which reduces power) to keep the engine from knocking. Very easy to use.

'Pro'
You have 3 options:
1) To let program set spark advance which produces best power.
2) To let program predict Burn Rate (required spark advance) and modify it by a user defined spark curve with 4 break points.
3) To let you specify the spark curve with 6 break points, and tell the program this curve produces best power. This effectively lets you specify the engine's burn rate.
Program calculates Knock Index, which gives the likelihood that detonation will occur. You can run with very low or high detonation. The programs time consuming calculations and method of calculation does not lend itself to letting the program automatically limit spark to a predetermined max allowable Knock Index.

--------------------------------------

Originally Posted by Gordo in Comox
awaiting the data that will give me the best possible engines for today's conditions.
Be patient a little longer. I need to be 100% confident of the parameters in the DBD simulation before I move on to the other models (starting with your ZB) since the DBD parameters will help me determine the others.

Over the next few days I plan to list all the relevant input data for 'Engine Analyzer Plus' that I'll use, along with the assumptions I make (e.g. 'hemi' for head type, vs. 'pent roof', 'wedge', or any of the eight other choices), so any mistakes I've made can be caught and any missing information filled in. Starting with the actual data for the DBD that are required inputs to the program:

DBD Clubman and Competition
bore: 3.346"
stroke: 3.465"
rod length: 6.469"
inlet port dia.: 1.5"
inlet port length: 5.21" [*]
inlet valve: 1.85"
exhaust valve: 1.53"
exhaust header length: 31"
twitter length: 26"

DBD Catalina
--same as Clubman, except:
inlet port dia.: 1.188" (¿need to check this)
exhaust pipe length: 49½"

[*] For the inlet ports I used the lengths shown by arrows in the first attached figure, extracted from p.22 of 'Goldie', that I calculated assuming the port diameters were the sizes of the carburetors supplied those years. Note that these are for 350 cc heads but, unless someone can supply more accurate data, I will be using these as "best estimates" for the various 500s. However, even if the inlet port lengths extracted from the figure were correct to the nearest 0.001" there is still wiggle room in the calculation. At full throttle the air resonating in the inlet tract can't tell any difference between the ~5" length of 1.5"-dia tract (for a DBD; smaller for earlier models) that's physically part of the head and the 6" length of the 1.5"-dia. GP that's bolted to it. At partial throttle the resonance is more complex but, like at full throttle, the tract of the carburetor alters the length of the "inlet tract." The point is, the quality of these simulations depends on as much on the quality of the assumptions that have to be made as it does on measured dimensions.

Once all the parameters are determined for each series ZB through DBD, the variables to test will be cams and compression ratios. It will take some time to convert all the cam data to the format used by the program. As the second figure shows,[**] by my count by the time we're done it will have required data on 5 inlet cams and 3 exhaust cams to cover the possibilities. But, that should take care of it even if Gordo builds his ZB to race on sand using alcohol (in his bike, not in him).

[**] The figure is a composite of tables in a May 1952 Instruction Book at the top and an August 1955 Maintenance Manual at the bottom. Other than the lack of a Touring model the DBD cams were the same as the DB so this figure covers all models from ZB through DBD.


Attached picture GoldStarHeads.jpg
Attached picture Cams_Gold Star.jpg
Visually, there doesn't appear to be a lot of difference between the Clubman and Touring cams, but looks can be deceiving. The area under the Clubman curve is 33% greater which potentially gives the engine enough extra fuel to make the difference between 30 h.p. and 40 hp. Similarly, the overlaps might not seem very different, but it is 72% greater for the Clubman cams so not all the fuel sticks around the combustion chamber to help with the h.p.

Attached picture Cams_Clubman_Touring.jpg
MM; In the BB engines the BB34 GS head (65-1501) is not as tall as my BB32 GS head and has a different inlet angle. It appears that the 32 was a complete development stage ahead. It was as if that version of a 34 head was just a carryover from the one piece head but with the change to the separate rockerbox.

To make sense of this I looked at your "Part numbers for heads" thread and see that you have for the BB engines Clubmans 65-1802 and 65-1805, Road Racing 65-1604 and 65-1501.

My 500 heads are 65-1501 and the 350 head is most likely a 65- 1802.(hard to make out numbers). That would mean that I am comparing Road Racing 500 heads with a Clubmans 350 head and find that the Clubmans head is more advanced, more like the later big fin heads. Have you sorted out the years/models that had both Clubmans and Road Racing versions for your simulations?

Does anyone out there have the BB Clubmans heads (65-1805) for comparison?

Gordo

PS interesting cam graph
Originally Posted by Gordo in Comox
It appears that the 32 was a complete development stage ahead.
The author of 'Goldie', nominally A. Golland but apparently BSA employee Arthur Lupkin, makes it clear that until the mid-'50s the development effort went into the 350s with the 500s benefiting later by trickle down (trickle up?)

Originally Posted by Gordo in Comox
Have you sorted out the years/models that had both Clubmans and Road Racing versions for your simulations?
When I offered to do this I was oblivious to the fact I would be entering uncharted territory, at least as far as Gold Star engines are concerned. Engine simulation software has been around for several decades but apparently(?) no one has applied it to Gold Stars. Which is surprising given that the large number of factory cams and pistons, not to mention gearboxes and sprockets, makes it a customizer's dream. Anyway, although uncharted territory means the going is slow, the fact no one has been here before means the rewards are great.

After a bit of frustration I finally realized (...I think...) that the opening/closing data for BSA cams aren't for the cams themselves, which is the common way of specifying things in the automotive world, but rather are for the valves. Since the lifters are 1"-dia. a valve will start opening sooner in angle than if the lifter were the diameter of the tip of a dial indicator as used to generate cam data, and will close later. So, my current top priority is to overcome the camshaft obstacle, requiring "translation" from the BSA "valve spec." data to industry-standard "cam spec." data.[*]

Originally Posted by Gordo in Comox
PS interesting cam graph
Ignore that graph since I'm now pretty sure it's a "valve lift graph," not a "cam graph."

[*] So far I've not found an on-line calculator for this so am presently dead in the water. Since all the cams have the same base circle, if someone has "real" cam data on any of the BSA camshafts that would be enough to know what constant to subtract from the opening and closing of all the valve specs to convert them to cam specs. I'll see if I have a loose BSA cam in the garage, in which case I'll be able to measure the offset. However, I'd much rather not spend the time doing that so I hope someone comes up with actual data in the next day or two.
Increased cam follower radius is similar to a steeper face on the cam . How you factor that it in I dunno,change the cam max open time parameter , if it cant handle ignition, probably not. I have a graph ( chart) showing the difference somewhere , has most effect at mid lift. A flat cam follower makes the sine wave fatter,
Originally Posted by gavin eisler
How you factor that it in I dunno,
What's the point in having a garage full of rusty BSA parts if you don't make use of them? Thanks to my labeling system ("Rusty BSA Parts Shelf #1, Rusty BSA Parts Shelf #2, ...) I quickly found a box with a half-dozen cams. But, they weren't necessary because when I then dragged a set of B34 cases down from the shelf it already had cams in it. Less conveniently they turned with difficulty, but a little penetrating oil quickly dealt with that.

I'll be making a more careful measurement soon, when I have more time, but for now I counted the no. of teeth on the cam between the tappet just starting to open, and just finishing closing. That was 12.5 teeth, times 10-deg./tooth = 125-deg. x 2 = 250-deg. engine. The part number is on the cam, but since these are just interim measurements I won't take the time to try to find where their specs. might be listed to see how well it matches. I'd estimate my ability to count fractional cam teeth is within 1/4, corresponding to an uncertainty of ~+/-5-deg. engine.

I then removed the tappet and installed a 2" dial indicator. Conveniently the ID of the tappet guide is the same as the OD of the indicator making this easy. With the tip of the indicator rather than the 1"-dia. flat of the tappet the two sides of the lobe were 11 teeth apart = 220-deg. engine. So, for draft simulation purposes I just have to subtract 30 degrees from the duration of each valve spec. to get the duration of the respective cam.

After doing this, inputting the cam values to the program, and tweaking the parameters to get a reasonable, but not perfect fit with Clubman cams, it showed ~40 h.p. at 7000 rpm. Simply switching to Touring cams dropped this to a reasonable ~30 h.p.

Don't memorize these numbers because they'll change once I enter more precise cam data as well as spend some more time tweaking the parameters in light of them. The important thing is, thanks to rusty BSA parts shelves, I'm no longer dead in the water.



Attached picture CamSpecAdjustment01.jpg
Attached picture CamSpecAdjustment02.jpg
MM: Nice work. The team is watching with baited breath and is rooting for your success. A drop of 25% in hp is a fair amount.

Gordo
As a reminder from another thread::
Originally Posted by Magnetoman
Thanks to several people I now have BSA sheets containing the dyno data plus the following relevant data:

ZB Scrambles, one-piece head, -2438/-2436 cams, 8.00:1, 1-5/32" TT, 49" straight pipe

BB Scrambles, 2438/-2436 cams, 8.60:1, 1-5/32" TT, 1-5/8" x 53" straight pipe
BB Touring, -2448/2450 cams, 8:00:1, 1-5/32" TT, silencer

CB Scrambles (same head as on CB Clubman), -2446/-2446 cams, 9.00:1, 1-1/8" Monobloc

DBD Clubman (sheets from 1956 and 1960 machines)
DBD Competition, 10:1, megaphone
DBD Scrambles (Catalina?), -2446/-2446 cams, 8.75:1, 1-5/32" Monobloc, 51" straight pipe

Note the lack of data as yet on any pre-DBD Clubman, so keep those dyno sheets coming (emphasis added).
The more data I have to narrow down the range of parameters, the more accurate the simulations that will be produced. As a simple example, the inlet tract and exhaust pipe lengths both affect the calculated results (although not in exactly the same way), so it's possible to get "reasonable" fits to a single dyno curve for a range of both of these. However, having dyno data on different configurations narrows the range of parameters that give "reasonable" fits.

I'm still in the stage of "training" the software so the more data I can feed it, the better. If, say, there were data on both the CB Scrambles and Clubman (same head but different cams and exhaust), and if the parameters were adjusted to fit both, confidence in having a correct result if simulating, say, substituting Road cams would be increased. So, keep those dyno sheets coming.
MM: The sheet I provided for the ZB 34 GS 4014 was Scrambles Specs but that is a Clubman head.

I am anxious to see a sheet for the Clubman BB 34 head to see how it differs from my Road Race BB 34 GS head. I have not yet heard back for the GSOC about sheets.

Gordo
Originally Posted by Gordo in Comox
was Scrambles Specs but that is a Clubman head.
After picking the type of combustion chamber, CR, and valve layout, the variables the program uses for the intake of a head are:

valve dia.
average port diameter
port length
flow efficiency

The first two are determined by measured dimensions but, for reasons I discussed in a previous post, the optimum value of port length won't necessarily be exactly one of the values shown by a red arrow in a post of two days ago. Flow efficiency is a percentage that the program says can vary from 25% for a 'bad flathead' to 55% for a 'racing head' to 65% for an 'excellent racing head' to 75% for the 'best racing heads available today'. For the particular simulation I have set up in the program at the moment, changing from 55% to 65% has a ~5 h.p. effect at 7000 rpm.

Anyway, I'm speculating at this point, but I predict that after fitting the data I'll find the best-fit port length and flow efficiencies of, say, BB Clubman and Scrambles heads to be pretty close to each other. That said, as the 55/65% example in the previous paragraph shows, "pretty close" still results in significant differences in the output. Which is why the more measurements I can feed the program, the better the simulations will be. Looked at another way, it will be interesting to see if systematic increases in flow efficiency are shown by the simulations when going from ZB through to DBD.

Today's task is to make careful measurements of the cam duration with and without the tappet so I can have accurate data for the BSA cams to enter in the program.


The first photograph shows I made a spacer for a cam and used rubber cement to glue a protractor to it using a rod with a small dimple from a center drill to locate it. I then glued the spacer to the cam, again using rubber cement. Since I had the engine on its side neither joint had to be very strong as long as I didn't bump it, which I didn't.

As can be seen from the second photograph, using a fine wire in a stud let me read angles to 0.25 degrees (0.5 degrees engine). I found conflicting information on whether BSA's cam specs are from measurements made at 0.014" or 0.018" lift so I measured both. It makes a 5.0 deg. difference in duration depending on which value of lift is used so it's important to figure out which is the correct one.

The third photograph shows how I made the measurements with the lifter in place, and the fourth photograph shows the measurement with a dial indicator having a point tip (using 0.014" for both of these photographs). Taking several measurements each and averaging I arrived at 28.5 +/- 1.0 deg. (0.014" lift) or 33.5 +/-1 deg. (0.018") as the angles to subtract from BSA's valve data for duration to convert to cam duration.

For example, BSA shows for the 65-2442 inlet cam that the valves open 65-deg. before TDC and close 85-deg. after BDC for a total duration of 330-degrees. To convert this to the cam duration you need to subtract either 28.5 or 33.5, depending on which lift is the correct one. I hope someone can point to a piece of BSA factory literature for the correct information.[*]

Since the cams are symmetric, to find the opening and closing angles of the cams you would subtract half this value. For example, since the valve opens at 65-deg BTDC the cam opens at 65 - 28.5/2 = = 48.25-deg BTDC (if the 0.018" value is the correct one to use).

So, today's burning question is, 0.014" or 0.018?[*] Accurate simulations await the answer.

[*] It's 0.018". I found it in a 1955 BSA 'Gold Star Data Book'.


Attached picture CamSpecAdjustment03.jpg
Attached picture CamSpecAdjustment04.jpg
Attached picture CamSpecAdjustment05.jpg
Attached picture CamSpecAdjustment06.jpg
This would explain why, 30 years ago, when I plotted data on many cams to find the ones closest to the factory specs, none came close.

I will see if I still have the plots on graph paper in an old file..it might explain a few things to me now!
"After a bit of frustration I finally realized (...I think...) that the opening/closing data for BSA cams aren't for the cams themselves, which is the common way of specifying things in the automotive world, but rather are for the valves."

I'm surprised that your simulation software wants to use cam data rather than valve lift data to predict performance. Isn't the valve lift data more relative to performance than what happens at the cam lobe? Megacycle states that their cam data is measured at the pushrod for pushrod motors, so even those numbers are not what happens at the valve which depends on tappet radius as well as rocker ratio. For example, Megacycle's data for the BSA B50 X4 cam is measured at the pushrod using Megacycle's specified 3/4" radiused tappets, but you can get them to grind tappets at 1-1/4" radius to get more duration as well as overlap.

You could, of course, degree one of your known BSA Goldstar cams to compare with the published data to see if it correlates.

Tom
Originally Posted by koncretekid
I'm surprised that your simulation software wants to use cam data rather than valve lift data to predict performance
The simulation software allows a person to explore effects of rocker ratio, lifter type and diameter, and valve train type (i.e. three types of pushrod/rocker, which I haven't fully explored as yet). To do this requires having raw cam data. Since BSA's valve data has the 1"-dia. tappet baked in it wouldn't be possible to explore the effect of different lifters if the program used valve lift rather than cam data.

Originally Posted by koncretekid
You could, of course, degree one of your known BSA Goldstar cams to compare with the published data to see if it correlates.
That thought crossed my mind, but only for a microsecond before I dismissed it. I'm not going to pull the cams from any of my engines for this project. Also, I degreed my Ariel's cams so I know how to do it, as well as know how long it takes to do it. So, I'm not even going to look through my boxes to see if I have any Gold Star cams (the ones I used for the measurements over the past few days have different numbers so are likely B31 or B33).

Originally Posted by Kerry W
This would explain why, 30 years ago, when I plotted data on many cams to find the ones closest to the factory specs, none came close.
To be fair to BSA, they were consistent about calling it "valve timing." That said, every time I've seen tables of those tabulated values I assumed it was cam data, and as a result it was a frustrating few hours of running simulations whose output was counterintuitive before I realized the source of the problem. It does make sense that BSA listed the values the way they did because 99% of the riders who cared about swapping cams would have wanted to know their effect on the valves. The raw cam data would have been useless to them.

Maybe someone has written about BSA's "valve vs. cam" issue previously, but I don't remember reading about it, and I couldn't find anything on the web. So, it was another shoal in these uncharted waters.

Two other shoals I'm dealing with at the moment are the Catalina head and the nature of BSA's dyno data itself. If I had a DBD Catalina and Clubman head on my workbench I could measure the length and diameter of the inlet tracts. Comparing how much the measured length of the Clubman's tract differs from the value I used in the simulation would tell me how much I needed to adjust that of the Catalina. I also need the diameter.

I've mentioned in at least one other thread that the BSA dyno data is too good to be true. Some of the dyno sheets are plots, but others contain what are supposed to be the raw data. The attached curve is a plot of that raw torque data for a CB Scrambler. Note that the first three data points lie precisely on a straight line. If any of the three measured torques had differed by as little as 0.05 (i.e. 0.16%) from the plotted values a straight line through any two points would miss the third. The same would be the case if the measured rpm for a given data point had differed by as little as 50 rpm (also ~0.15%) from the precise values of 2500, 3000, etc.

OK, now imagine yourself in front of an engine dyno in a noisy, smelly room with a 40 h.p. engine vibrating on its mount while you adjust the throttle to reach each new setting of rpm and then read the analog torque gauge. Do you think you could adjust the throttle of this vibrating engine to hold it at precisely 3500 rpm to within 0.15%? And, even if you did, do you think the torque reading would fluctuate less than 0.15% and that you could read it to that precision on an analog gauge? OK, the answers are no, which means the data on these engine dyno tests are fake. Well, not completely fake, but "dry labbed."

I can only guess but a plausible scenario is a "master engine" in a given configuration was measured and the data, complete with fluctuations, was plotted. The draftsman then drew a smooth curve that was best-fit to that data, along with a set of parallel curves somewhat higher and lower than that curve. From then on "production" engines would be tested at whatever rpm had been decided on for this configuration (say, aim for 6500 +/-200) and the torque measured to whatever accuracy was achievable (maybe 1%). Whoever was in charge of producing the dyno sheet found the plot for the relevant configuration in a notebook, noted the measured rpm (which wouldn't have been precisely 6500) and torque, located the parallel curve on the master plot that was closest to that data point, and then "dry labbed" the entire curve based on it.

The reason this is relevant for this thread is, among other choices I have to make, I have to decide how well the parameters I choose need to fit a "measured" BSA curve across its entire range of rpm.


Attached picture BSAvalvespecs.jpg
Attached picture CBScrambler_torque.jpg


I have a Catalina head sitting on my workbench, where it awaits installation after I pluck up the courage (and find the time) to install my shiny new Pearson crank in the cases and actually build the engine. So I will be happy to do the measurements for you this weekend.

Also, regarding carbs, since my Catalina air box is also sitting on a shelf, I can send that to you for your flow test. Seems a shame to take yours off when you have your Catalina running so sweetly, and before I get a chance to break it.
Originally Posted by NYBSAGUY
since my Catalina air box is also sitting on a shelf, I can send that to you for your flow test.
Thanks for that offer, but since it is held on by only two bolts I can remove mine in less time than it would take to re-box yours and take it to the UPS office.

Basically, air flow has a linear effect, but the inlet tract creates a resonance so its effect is non-linear. Because of this the air flow through the carburetor and filter (if any) has an effect on the simulation, but much more significant are the dia. and length of the inlet tract that correspond to the red arrows in a previous post..

The second image is from a test sheet someone sent me, for a BB with Touring cams. As can be seen, the h.p. increases smoothly to ~5500 rpm but then hits an inflection point. My Catalina simulation shows the same type of behavior. Changing the carburetor air flow raises or lowers the overall curve (the effect increases with increasing rpm), but changing the port length or diameter moves the inflection point to higher or lower rpm.

I easily can pick parameters that move the inflection point to higher than the 6500 rpm upper limit of the Catalina test sheet (which doesn't show this in the measured curve, so it's higher than 6500 rpm), but the program has enough parameters that I probably could make a h.p. vs. rpm curve look like the New York skyline if I didn't impose physical constraints (like actual valve diameters, inlet tract dimensions, etc.). Hence, I eagerly await your Catalina measurements.


Attached picture BB_Touring.jpg
It's entirely Gordo's fault that I'm spending my time on these simulations so it's only fair that I inflict a draft ZB Scrambler simulation on him without further delay. I'm still labeling it as 'draft' but I hope to take that qualifier away as soon as I have the Catalina head data to use in another check of my parameters.

All I did to turn the DBD Clubman simulation into a ZB Scrambler simulation was to change to the ZB's 8:1 piston, cams, 49" straight exhaust, and valve diameters. In addition, I used:

1.21"-dia. inlet (given in earlier post by Gordo)
3.6" port length (from red arrows in drawing in a previous post)
5% less flow for the 1-5/32" TT than I measured for a 1-3/16" TT
1-5/8" exhaust diameter (is this correct for a ZB?)

For the attached graph I simply traced the BSA data in a new layer in PhotoShop so it would remain visible and then overlaid the simulation with its axes scaled. As I think people would have to agree, the fit is remarkably good, reproducing the shape very well and the absolute value to ~8% (the fit of the program to measured automobile dyno data is claimed to be +/-7%). I should note that the simulation also over-estimates the total h.p. of the DBD so the fact it does as well for the ZB is consistent.

Again, I first worked out a simulation for a DBD Clubman using physically reasonable parameters. I then simply changed only the relevant measurements (compression ratio, valve dimensions, cam specifications, etc.) and the result is shown in the graph. With each such result my confidence in the output of this program grows.

Of course, the point of doing this isn't to reproduce curves we already have, but to investigate the effects of making changes for which we don't have curves. That will come shortly, as soon as I have enough confidence in all the parameters to remove 'draft' from the simulations.


Attached picture ZBScrambles_draft.jpg
MM: My ZB head measures about 1.75 to 1.78 inches going around where the pipe goes into the head. Can't accurately measure if the opening is tapered or measure the actual opening that the pipe would butt up against.

Gordo
Originally Posted by Gordo in Comox
MM: My ZB head measures about 1.75 to 1.78 inches going around where the pipe goes into the head.
That sounds consistent with a 1-5/8" ID for the pipe.

In a previous post I showed evidence that BSA faked their dyno data. Even though no one came to BSA's defense when I made that accusation, I'll go further. The graph attached to this post is the same as the graph in my previous post except with the simulation displaced down to match the h.p. curve. As can be seen, the h.p. curves overlap almost perfectly. That's a good thing, right? But, what's the deal with the torque curves below 5000 rpm?

Torque and h.p. are linearly related through (torque x rpm) / 5252 = h.p. According to p. 52 of 'Goldie' the BSA dyno worked by balancing the engine output against a variable weight with (W(lbs.) x rpm)/4500 = h.p. The text doesn't give details but that weight would be at the end of a lever so would give the torque once the dyno was calibrated, which is where the constant 4500 comes from. Again, though, the torque and h.p. are linearly related. What this means is, if the h.p. curves overlap, the torque curves must overlap as well. If they don't, as is the case for the attached plot, something is rotten in Birmingham.

The three BSA dyno pages I've taken the time to check all have issues of the torque and h.p. curves not being correctly related to each other. So, do I use parameters that best fit the torque curves, which is what the BSA dyno actually measured, or the h.p. curves that they calculated from the dyno data? The problem is, once you know some data is faked, all data is subject to suspicion. I won't take the time to explore this issue further here, but it's yet another factor to contend with in trying to decide on the parameters that best simulate BSA's "data." Oh what a tangled web BSA has weaved.


Attached picture ZBScrambles__displaced_draft.jpg
Have been away for a couple of days and just catching up with 'Dynogate'.

30 years ago it struck me that the curves were all too 'nice' to be true and that the reality must have been data points scattered above and below the charted line...though I assumed the general trend reflected the engine it was related to, especially the peak power. I've never seen a BSA graph that showed the power peaking and dropping, with RPM pas peak power RPM, as I'm used to seeing with my 2 strokes. The impression is that there is more power at higher RPM, if you're brave enough to go there, or can accept the consequences ($$).
Originally Posted by Kerry W
just catching up with 'Dynogate'.
A. Golland, the nominal author of 'Goldie', has been identified as being the BSA development engineer Arthur Lupton. Lupton says about the dyno testing that "The engine was run under moderate load for about an hour and then the standard exhaust pipe would be fitted, when power tests were undertaken at various engine speeds. ... a series of readings were completed in a very few minutes..." Lupton's description tells the reader that the dyno room produced careful, accurate measurements of every engine over the full range of rpm.[*]

At the height of production in the mid-1950s Gold Stars were despatched at an average rate of 5-7 per day. Bolting an engine in place, warming it up for an hour, testing it, then unbolting the hot engine and removing it from the stand barely allows time to meet that average production rate, let alone higher short-term rates when batches were needed for overseas orders.

Given the above, the dyno room would have been the bottleneck. If the guy locked in that hot, smelly, noisy dyno room knew a, say, good Clubman engine produced 31 h.p. at 5000 rpm as shown in the curve on p. 55 of 'Goldie' why not warm up an engine for just 30 min., run it up only to 5000 rpm to avoid any risk of damage, and measure the output at that single rpm? If it produced at least 31 h.p., use the time while it was being unbolted from the stand to drylab the full curve from the sheets in the test notebook, move on to testing the next engine in order to meet the production demands, and give the day's stack of dyno sheets to the supervisor at the end of the day to sign.

I'm not saying this is how the dyno "data" were produced. But, as the examples I've included in previous posts show, the "data" are too good to be true, and the torque and h.p. values cannot both be correct. This means something is amiss in the way those sheets were produced.

Again, the relevance for these simulations is having to decide at what point a given simulation fits faked data well enough to have confidence to use the parameters from that simulation to fit other faked data. The normal situation would be to develop a simulation that does a reasonable job mimicking known reality. Here, there's a good chance the simulations are more real than BSA's "reality."

[*] The attached image is the signature on a 1961 dyno sheet.


Attached picture DynoSignature.jpg
Did they only have one dynamometer?
Originally Posted by triton thrasher
Did they only have one dynamometer?
Good question. All I know about the situation is the description in 'Goldie'. On p. 54 it says "The dynamometers used for testing were of the hydraulic type. In essence these..." Golland/Lupton used the plural so either more than one dyno was in simultaneous use for Gold Stars, or it means over the years a single old hydraulic dyno was replaced by a single new hydraulic dyno, or he used the plural for stylistic reasons. Without more information, your guess is as good as mine. My guess is they only had one dyno in operation at a time in the Gold Star part of the plant.
If they used more than one, it wouldn’t have been a bottleneck.

It was a big factory.
Originally Posted by triton thrasher
If they used more than one, it wouldn’t have been a bottleneck.
Right. But it would have been just as easy to print the actual dyno data if they had them. But, since the evidence shows the "data" they supplied can't be real, I offered one plausible scenario that could explain why they might have done that instead of printing actual measured curves over the full range of rpm if they had them.

Ok, so Triumph is not the same as BSA, but their bikes did reasonably well, in all modes. Here is the situation at Triumph, in the engine department. And this is a verifiable fact, not just internet hearsay. The crankcases were cast in a shed on one side of the plant. Once enough of them were ready to go to the engine assembly room, they were loaded onto a cart and wheeled across an open yard to the assembly 'plant'. No matter that one set of cases had come straight out of the cast, or they had sat there since yesterday. All fine if it was a nice summer day, with the temps around 70F. What if it was a horrid, rainy, freezing winter day in the Midlands, with the mercury down in the low thirties? Same thing, the cases were thrown onto the cart, and wheeled across the freezing yard to the engine assembly plant.

The point of this anecdote is that the problems with British manufacturing during the 50s and 60s have been well documented, and would ultimately lead to the demise of an entire industry.

So it is barely surprising if BSA knocked out a few dozen made-up GS dyno sheets in a week, while they were busily trying to persuade the Great British Public of the merits of their latest iteration of the already defunct 175cc BSA Bantam.

Oh dear, have we shattered the myth of the individual engine test sheet? I would be happy if at least the max hp/rpm reading was correct.

Gordo
Originally Posted by NYBSAGUY
So it is barely surprising if BSA knocked out a few dozen made-up GS dyno sheets in a week,
Originally Posted by Gordo in Comox
I would be happy if at least the max hp/rpm reading was correct.
The lack of shock or outrage about this revelation is interesting. It's like learning the high school valedictorian cheated on every test since kindergarten and shrugging our shoulders.

Actually, just because the valedictorian cheated doesn't mean he also isn't smart. It only took a few sheets to determine BSA cheated so there's a reasonable chance that if Gordo gets his hands on more dyno sheets we might be able to infer from them what is fake and what is real.
Time will tell on the sheets. I find it hard to believe that they would sit down and fill out a fake sheet for each and every engine given the detail contained on the sheet. With a few lads to help move the engines through the process I could envision all the engines getting their time on a dyno.

Of course Santa Claus did leave me an electric train under the tree one Christmas.

Gordo
Originally Posted by Gordo in Comox
I find it hard to believe that they would sit down and fill out a fake sheet for each and every engine given the detail contained on the sheet.
I think it was you who sent me two sheets on a BB, both listing 25-5-53 as the day it was tested. One sheet appears to be a dyno room worksheet while the other, based on it, is the what would have been given to the customer. At the top of the attached composite is the data from the first sheet, and at the bottom is the curve that is plotted on the second sheet.

The first sheet shows two sets of b.h.p. and torque values, with the upper row of both the ones that are plotted on the second sheet. These values are slightly higher than the lower row. The first sheet lists the brake constant as 4500. That's what is given on p. 55 of 'Goldie' as the calibration constant for the dynamometer BSA used, where it also gives the formula h.p. = W(lbs.) x rpm / 4500. Using the Brake Load values on the first sheet along with this formula gives:

rpm__ calculated h.p.
4000 19.6
4500 21.2
5000 22.7
5500 23.7
5800 23.3

These are the same as the bottom row, which are slightly lower than the figures on the top row. Everything on the first page is written by hand, with the pen that was used for everything other than the two lines of h.p. and torque data leaving lines that are sharp and black.

Going out on a limb with wildly unsubstantiated speculation, it appears to me that all of the data on the first sheet actually may be real. Further speculation is that the engine may have initially failed the dyno test based on the operator just looking at the weights recorded from the dyno. If this is the case, I'll speculate the 19.4 lbs. (23.7 h.p.) at 5500 rpm the operator recorded directly from the dyno was too low to pass so the engine was fiddled with and retested. It hit 20.6 lbs. (25.2 h.p.) on the second test, which apparently was enough to pass. The two lines written with a different pen were to check the before and after values, with only the 'after' values plotted on the second page where all the specifications of this engine are typed. That is, the first page was a worksheet filled out in the dyno room, and the second page prepared later with a typewriter.

Based on too little data my current hypothesis is in the early '50s they were carefully taking complete dyno data, but by the late '50s they were sloppier, taking minimal data and faking the rest. More dyno sheets will help confirm whether or not this speculation is correct, needs modification, or is totally wrong.



Attached picture Dyno_BB_composite.jpg
I have a certificate of performance for my ZB32GS from 1950, this is not a curve but a typed certificate showing engine serial number, cams, carb, jets and cut away, max safe RPM .. etc - is this what you are looking verify?
There is no curve or power output shown
Originally Posted by David Cass1
I have a certificate of performance for my ZB32GS from 1950,.. There is no curve or power output shown
BSA used several formats over the years, at least two where the configuration information is typed on the left half of the sheet and the curve is on the right. Is it possible whoever sent your sheet to you only copied half of it? By chance, is there a line at the bottom that says B.S.A. CYCLES. LTD., Technical Dept.... and is BIRMINGHAM at the end of that line cut off?
Yes, the certificate reads as you describe.
It is a single page, therefore, possibly only half of the test.

David C
Ireland
Today I heard from Ian Jackson, GSOC, and he is not able to send test sheets but he reminded me that Jon Luke now has them all. However he did give me some engine numbers of BB32 GS machines that were despatched in rigid frames. and some DB34 GS engines despatched in rigid frames. Could these be Trials engines or are these Daytona rigid or Flat track BB32R type frames?

I have passed these on to Jon and asked if he has any engine sheets for them.

Gordo
Originally Posted by Magnetoman
Originally Posted by triton thrasher
Did they only have one dynamometer?
Good question. All I know about the situation is the description in 'Goldie'. On p. 54 it says "The dynamometers used for testing were of the hydraulic type. In essence these..." Golland/Lupton used the plural so either more than one dyno was in simultaneous use for Gold Stars, or it means over the years a single old hydraulic dyno was replaced by a single new hydraulic dyno, or he used the plural for stylistic reasons. Without more information, your guess is as good as mine. My guess is they only had one dyno in operation at a time in the Gold Star part of the plant.


There is a period picture floating around of the "Din Room" showing 3 or 4 Goldie motors all hooked up.
Those of you who follow me on Instagram will know I spent the last three days in Sedona surrounded by energy vortexes, aura photographers, energy crystals, New Age psychics and chakra balancers. Dripping with excess energy, my dynamically rebalanced chakra is now back in the desert ready to return to Gold Star simulations.

Thanks to Gordo of the Comox and Jon Luke of the GSOC, waiting for me were the necessary dyno sheets that I need to "calibrate" the simulation program. So, stay tuned. In addition to providing me with needed data, these sheets directly show the progress BSA made with these machines. Taking Clubmans as an example, from a ZB tested in 1950 through to a DBD tested in 1960, the peak h.p. was:

ZB 32.0 @ 6400 rpm
BB 34.2 @ 6200
CB 37.9 @ 6000
DB 37.6 @ 7000
DBD 40.0 @ 7000

For comparison, a B32 DB Clubman produced 32.4 h.p. @ 7000 rpm. And, compared to the wimpy 40.0 h.p. that a DBD Clubman produced for the English market, the U.S.-only Competition's output was a manly 41.7 h.p.

I only have one sheet for the CB Clubman. Its peak was 37.9 h.p. at a rather low 6000 rpm but it dropped only slightly, to 36.9, at 6750 rpm. Especially given the large jump in h.p. that the CB achieved over the BB, I wonder if they decided at that point during the development of the B34 that it might be better to tune it for a broad spread at the expense of somewhat reduced peak h.p. Hopefully, the simulations will shed light on questions like this.
Originally Posted by Magnetoman
Clubmans ...
ZB 32.0 @ 6400 rpm
BB 34.2 @ 6200
CB 37.9 @ 6000
DB 37.6 @ 7000
DBD 40.0 @ 7000
Continuing on the theme of steady improvements, for Scrambles:

ZB [email protected]
BB [email protected]
CB [email protected]
DB [email protected]
DBD [email protected]

Comparing these figures with for those of the Clubmans, again the big leap forward happened with the CB. However, unlike the Clubman, they seem to have decided ~35 h.p. was sufficient for a scrambler so didn't try to eke out more. It will be very interesting to compare the torque curves when simulating these two configurations.
MM: I would agree that the DBD scrambler was really about torque. It had a real ability just keep pulling you forward through muddy conditions or up inclines. It was not too fussy, within reason, about which gear it was in and it was hard to bog it down. I am looking forward to your results.

Gordo
Originally Posted by Magnetoman
Originally Posted by Magnetoman
Clubmans ...
ZB 32.0 @ 6400 rpm
BB 34.2 @ 6200
CB 37.9 @ 6000
DB 37.6 @ 7000
DBD 40.0 @ 7000
Scrambles:
ZB [email protected]
BB [email protected]
CB [email protected]
DB [email protected]
DBD [email protected]
Ending this overview, Touring:
ZB [email protected]
BB [email protected]
CB [email protected]

What a difference a pair of cams makes, eh? (and a silencer, and the inlet tract, but mostly cams). For the CB the difference is 43% between a Clubman and a Touring. I have no idea what cams are in my BB but, given the former owner managed 100 mph on the ZB34 bitza he built that's now owned by NYBSAGUY, I suspect he didn't put touring cams in either of them.
Originally Posted by Magnetoman
Originally Posted by Magnetoman
Originally Posted by Magnetoman
Clubmans ...
ZB 32.0 @ 6400 rpm
BB 34.2 @ 6200
CB 37.9 @ 6000
DB 37.6 @ 7000
DBD 40.0 @ 7000
Scrambles:
ZB [email protected]
BB [email protected]
CB [email protected]
DB [email protected]
DBD [email protected]
Ending this overview, Touring:
ZB [email protected]
BB [email protected]
CB [email protected]

What a difference a pair of cams makes, eh? (and a silencer, and the inlet tract, but mostly cams). For the CB the difference is 43% between a Clubman and a Touring. I have no idea what cams are in my BB but, given the former owner managed 100 mph on the ZB34 bitza he built that's now owned by NYBSAGUY, I suspect he didn't put touring cams in either of them.


Hi guys, just jumping in as a new forummember, although reader for a long time, this topic, and to be more specific this last part, made me to make an account and jump in..

maybe i missed something, but the above quote's do not mention the difference between "x" B32 GS & "x" B34 GS,

if really the output of the "x"B34 GS is meant.. i think some hp claims should be to decern / nuance more..

for instance a ZB34GS in touring trim with the same output as a standard B33 ?? could be in Reliability Trails trim , as these have the same camshafts as a basic B33 , but as a ZB34 GS in touring trim would had left the factory with 65-2438/65-2448 inlet camshaft and 65-2436/65-2450 outlet camshaft the same as the scramblers in those years as far as i know, i think the output was more..
even in those early years and i think in all the GS years, Reliability Trails (standard basic camshafts) is NOT the same as Touring trim with (slightly) more advanced/slightly more sporty camshafts.. atleast in Europe i think..

but maybe i am wrong...

best regards
Harold
Originally Posted by Motolab
maybe i missed something, but the above quote's do not mention the difference between "x" B32 GS & "x" B34 GS,
I thought I had mentioned earlier in this thread that in the interests of keeping the simulations to a reasonable number I only would be dealing with 500 cc Gold Stars, at least for the time being. I should have mentioned that again. Sorry for any confusion.

Originally Posted by Motolab
a ZB34GS in touring trim with the same output as a standard B33 ??
I'm unaware of factory dyno data on B33s. Where did you get your data?

Originally Posted by Motolab
a ZB34 GS in touring trim would had left the factory with 65-2438/65-2448 inlet camshaft and 65-2436/65-2450 outlet camshaft
The ZB34 whose output I quoted is listed by BSA on the November 1950 dyno certificate as having "Touring" specification, "standard pipe and silencer," and with 65-2420 cams for both the inlet and exhaust. I realize that other BSA literature (dated 1952) lists these as recommended Trials cams, but I've followed BSA's lead on what they called the final machine.

I don't have enough information at hand to do more than speculate, but this particular bike was built fairly early in the life of ZB34 Gold Stars. Perhaps they hadn't realized at that point that customers wanted more peppy performance from their Touring machines than given by 65-2420 cams and then later "upgraded" the specifications for Touring models. However, that's just speculation based on the date of the machine.

I don't want to argue whether or not they "should" have listed it as a "Touring" bike because for the purposes of running simulations it doesn't matter what they called any of them, only what specifications the engines had. The names they used are just a convenient way of organizing the information. When I finish each simulation and list the output it will be along with the cams and other relevant technical information. With or without simulations, someone is free to use 'Clubman' cams to build a 'trials' bike and call it a 'scrambler' if they wish.

A couple of points leap to mind as I read the above.

First, yes, I do now own and ride the ZB34 'bitsa' described above, and I have the builder's notes, where the builder indeed affirms that he had it going at 100mph. What he doesn't say is whether it blew up the moment he hit the 'ton', or whether he rebuilt it after he got it home. I have had it up to a whopping 52mph, and at that speed it threatens to buck me into the nearest ditch, so I backed off to a more manageable 42mph.. I presume the hot cams are still in it, because it accelerates like a modern scrambler.

Second, A.Golland was really Arthur Lupton., eh? And Adolf Galland was the WW2 Luftwaffe flying ace known to every schoolboy in the post WW2 era (including me). So why was Mr Lupton impersonating Leutnant Galland. Someone here must know.

With apologies to MM for digressions. But he started it.
Originally Posted by NYBSAGUY
So why was Mr Lupton impersonating Leutnant Galland.
I'll go way out on a limb and speculate that Golland was Arthur's middle name. And, in light of your post, I'll go further and speculate that he, like the Royal Family, was a secret German. Although, the 'Golland Heights' in northern Israel might mean he was a secret Syrian or secret Israeli.


Attached picture Golland.jpg
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This is happening in quite a few threads lately , Can't view attachments or pictures ,
NYBSAGUY

There must be something really wrong with your ZB, The ZB34GS machines running in the Isle of Man Clubman TT were averaging around 80 mph so most likely were up around 100 mph on the quick sections.

Gordo
Originally Posted by Gordo in Comox
There must be something really wrong with your ZB,
He has a Catalina, but his bitza isn't a Gold Star, but rather an iron-head ZB34 in an M20 frame. The builder's notebook says he managed 100 mph on it (after which the liner slipped and he had to rebuild the engine), even though NYBSAGUY feels he's about to be thrown off the road at half that speed. My BB and Catalina came from the estate of the same builder.
MM: I missed that subtlety, the 'bucking' issue could just be the M20 frame.

Gordo

He built beautiful BSAs alright. And he rode them, too, as his notebook illustrates wonderfully. But he was clearly nuts to ride this rigid, girder forked ZB34 at more than 50mph.
Originally Posted by Gordo in Comox
MM: I missed that subtlety, the 'bucking' issue could just be the M20 frame.

Gordo
The funny thing is that the pre-War M23 Empire Star and M24 Gold Star used essentially the same frame and forks as the M20.
Could it be something as simple as tyre pressures? The rigid / girder combination needs much lower tyre pressures than telescopic forks and a swinging fork rear suspension.

The less said about plunger rear suspension the better smile
Originally Posted by Shane in Oz
The rigid / girder combination needs much lower tyre pressures than telescopic forks and a swinging fork rear suspension.
For many years I've run all my car, truck, trailer, and motorcycle tires at 90% of the max. inflation figure given on the side of the tires. For the Avon Roadriders on my Ariel that figure is 42 psi so by the 90% rule they should be inflated to 38 psi. However, at the suggestion of several people (BSA_WM20 and Chaterlea25 come to mind) I used 28 psi instead and was quite happy with how it steered and how it handled bumps. Well, "happy" with how girder forks and rigid frame handled bumps might be a bit of an overstatement, but I wasn't unhappy.
Originally Posted by NYBSAGUY

He built beautiful BSAs alright. And he rode them, too, as his notebook illustrates wonderfully. But he was clearly nuts to ride this rigid, girder forked ZB34 at more than 50mph.


I ride my M20 at speeds of 50mph or better regularly and it runs quite fine, rock steady , although others have noticed the rear rarely touches the ground .
Before I got the tyre pressures sorted out it was a nasty snarling beast doing it's best to toss me off so you will need to do some serious tyre inflation tests .
When the bike was way overgeared I was doing 70-80mph regularly with no handleing problems.
You might also need to have a good look at the fork damper, again there is a fine line between slowing down the front end and the forks throwing the back end around.
Same story for the steering damper, I have found the rigid frames handle much more predictably with the steering damper a bit looser than I would on a swing arm frame.
As little as 1/2 psi can make a massive difference to the handleing on a rigid.
There has been more than one 100mph M 20's kicking around by people with way too much spare time on their hands.
Now stopping from more than 50mph,,, frown that is a totally different story, of the brown undies variety. facepalm
I agree with all of the above. Tyre pressure can make a big difference so thats where I would start. Also setting up the girder/damper will make a difference too.

My 1939 Triumph is rigid/girder and is fine well over 50 as are loads of other bikes with similar frame/forks.

Once you have gone through the other checks and adjustments, if you need more improvement then I would be happy to sell you some snake oil 100% nitrogen that is bound to improve things over the mere 78% that you currently have. smile

John
Ha, thank you for all the suggestions, which are gratefully received. But I think I have hijacked this thread quite enough. MM might never talk to me again. Or worse, he might not rebuild my Catalina mag, and its oil pump too.

John, I'll take the 100% N. Send me a Paypal bill..

Turning from p.s.i. to b.h.p., I've been making progress getting ready for work on the actual simulations. The dyno sheets were issued in several forms over the years. The ones I have for ZBs and some BBs are single sheets with the heading "Certificate of Engine Performance" and with the specifications on one half and a graph of h.p. and torque on the other half.

Starting with some of the BBs and continuing through the DBs are full page "Engine Brake Test (Office Copy)" that list specifications along with the dyno measurements, but no graph. I infer from this that similar sheets exist, or existed, for the ZBs but these were kept on file with the relevant information copied to the "Certificate" that was sent to the customer.

For the DBD I mostly have sheets with the heading 'BSA Model B34 Gold Star Brake Test" with specifications plus dyno data, although I have one sheet with the specifications on one half and a graph on the other, similar to the ones for ZBs and BBs.

The office copies for the BB, CB, and DB have a lot of pre-typed specifications for the operator to circle (e.g. four possible carburetors, four ea. inlet and exhaust cams, etc.), but for the DBD this had been reduced considerably. Only two choices, "Scrambles" or "Clubman's" could be circled (on the sheet for my Competition the word "COMP" is hand-written between these two choices, but I don't know if something similar was done for a Catalina), "Monobloc" or "Grand Prix", "Magneto" or "Magdyno," and "Castor Oil" or "Mineral Oil." There's also a space for "Compression Ratio," but that's blank on all the forms, and "Ignition Timing," which is filled in at 39. Actually, this line is "___ deg. F.A. b.t.d.c." Does anyone know what the "F.A." means?

Four of these DBD sheets have only the "Brake Load lb." table filled in (with moderately sloppy penmanship), which is what was actually measured, but one of them has that line blank and the "B.H.P." and "Torque" boxes filled in (with neat, crisp penmanship), which were values calculated from the measured Brake Load. So, this sheet must have been filled in later.

Anyway, I'm working to get everything into a standard form that will be most useful to have when I start running the simulations. For this I'm creating h.p. and torque curves for every sheet where they don't already exist, which in some cases requires calculating these values from the listed Brake Load. Also, wherever Brake Load data is listed, and even if h.p. and torque values are on the sheets, I'm calculating those values myself since I've already determined that BSA slide rule operators weren't as concerned with accuracy as they could have been.
Hi MM
F.A. ? Firing angle ??????

John
Originally Posted by chaterlea25
F.A. ? Firing angle ??????
That would make sense, although a bit redundant. But your post made me look at earlier dyno tests. There for ignition timing they have "___ inch fully advanced before t.d.c." So, that answers it -- F.A. is the fully advanced timing value.
W built a twin engined M20 in our work shop, which was not too frightening at 70-90mph- we called it an M20/20- we changed the forks to tele as the girders were too worn

[Linked Image]
Having finished jetting my 'Competition', and with tests of the jetting in the BB and Catalina on hold until temperatures drop in the fall, I turned back to the simulation project.

Again, my technology-appropriate TI59 programmable calculator came in handy. As I mentioned before, a lot of the sheets only have the 'Brake Load lb.' line filled in so to get to h.p. I had to multiply that by the rpm and then divide by 4500 for the dyno BSA used. Luckily, I also have the instruction book because for some reason after 35+ years I didn't remember how to program it to allow for two inputs (load and rpm).

In addition to filling in the blanks I checked a few tables even though someone at BSA had filled in the numbers. Having found a pretty high percentage of errors (albeit, of only a few decimal points), and having the TI59 already programmed, I checked all the sheets.

Having the sheets in chronological order made it easy to notice that things didn't remain static even after the DBD model was introduced. Rounding off the engine numbers for Clubman's:

engine no.__ h.p. @ 7000 rpm
3600 _______ 36.7
4000 _______ 37.0
4600 _______ 37.3
5000 _______ 38.4
6000 _______ 40.0
7100 _______ 41.7 (Competition)

Leaving aside the Competition, to eke out an additional 9% in h.p between June 1958 and November 1960 is pretty significant.

At this point I now have all the sheets in order, the h.p. values calculated, and plots of h.p. vs. rpm for all 24 B34 engines so I'm diving into the simulations.
As a sort of progress report on the issues I have to deal with and where things stand at the moment with the simulations, after "experimenting" with the program I decided to start with Scrambles models first. As do other things, the exhaust system has a big effect on the h.p. vs. rpm. However, for my purposes Scrambles models have the advantage of having a simple 51" exhaust pipe so there's no megaphone resonance to deal with (which isn't included in the program).

With that decision out of the way, I started with parameters I already had worked on when I first started with a Clubman. I'll go into greater detail later, but tappet dia., "aggressiveness" of the cam profile, and many other parameters must be the same between models for the simulation to make any sense. That is, I have enough parameters at my disposal that if I didn't impose constraints I certainly could fit each curve separately, but doing so would be of questionably validity. Although some constraints are "fixed" (e.g. dia. of exhaust pipe), some aren't (e.g. "Ramp Rating %"-- an arbitrary value from 0-100% that represents the aggressiveness of the cam profile), but whatever I determine for the "free" parameters of one model will have to apply to another in order that these simulations make sense.

With that as much-too-brief background, the first graph shows a best-ish fit to a DBD Scrambles engine. I've offset the vertical axis of the calculated curve since the program doesn't claim high accuracy for the absolute h.p. As can be seen, the fit isn't all that great. However, this brings us to the point I've made before, that BSA's plots aren't to be trusted. In this case, the BSA curve I have is on a two-column sheet with all the information typed and only a drawn curve, i.e. no "data." So, it was created after the fact as a 'certificate' to ship to the customer.

I have a sheet for a DB Scrambles bike that does give the data. The second graph shows that data in red 'x's with the scatter in those points lending reason to believe it might be actual data rather than a figment of a draftsman's imagination. Also on the graph is a best-ish fit to the DB Scrambles engine, again with the vertical axis displaced. In this case the fit is much better. Presumably, it might even get better as I refine the parameters of the fit. Although, given what I expect the actual uncertainties of their dyno measurements to be, the fit wouldn't have to be any better in order to be a good fit.

Anyway, fitting data where some data might be data and other data might be faked requires making judgment calls as to what data should be given more weight than other data. This makes this simulation project more "interesting" than it already would have been.

Attached picture DBD_Scrambles.jpg
Attached picture DB_Scrambles.jpg
As one example of what I need to do to have confidence in these simulations, two input parameters for the intake port are the 'Average Port Diameter" and "Port Length." After experimenting with values I decided I had no choice but to actually measure these to know how much 'wiggle room' was available in the program. So, I pulled the carburetor from my 'Competition'.

The first photograph shows that the intake port is pretty much a straight shot to the valve and appears to be a simple cylinder for most of the length. However, more careful measurement with a split anvil gauge shows the diameter is ~1.468" for the first 1½", then tapers to ~1.488" over the next 1½" before reaching the cavity around the valve. As for the length, measured to the near edge of the valve seat it's ~4.75", and to the far end it's ~5.88", for an average of ~5.31".

Anyway, to see if these variations make any difference, I ran my draft DBD Clubman simulation with the nominal inlet port diameter 1.5" and length 5", and with the averages of my measurements of 1.48" and 5.56". Those results are shown in the graph.

It can be seen that these two sets of values make a considerable difference (actually, only a small fraction of the difference is due to the diameter). Anyway, I'm making (slow) progress.

Attached picture InletPort.jpg
Attached picture InletPort02.jpg
Attached picture Clubman_InletPort_variations.jpg
I'll be requesting some more data from people as soon as I'm sure I have a complete list of what will be required to simulate pre-DBD engines. Meanwhile, as an indication of the possible value of these simulations, attached are simulations of three DBD Clubman engines covering a fairly wide span of production.

I showed in a previous post that the max. h.p. of DBD Clubman engines crept upwards throughout the production run (by 3.3 h.p. for the five dyno sheets I have). Although most parameters (cam profiles, lifter dia., valve sizes, carburetor, etc.) did not change, where progress could have been made was in the inlet tract. I noted in my previous post that my Competition's head doesn't consist of a simple cylinder the entire length, but rather is a cylinder for the first 1½ and then tapers to a ~0.2" larger diameter over the next 1½". This small difference in diameter makes very little difference to the simulation, but where it might make a difference is in the "Flow Efficiency" of the inlet tract.

The program allows actual flow bench measurements to be entered but, where they're not available, it offers a dropdown list of suggestions that include:

70% Best Racing Heads Today (Winston Cup)
65% Excellent Racing Heads
60% Very Good Racing Heads
57% Good Racing Heads
55% Racing Heads

Keep in mind that the last of the DBDs was made more than a half-century ago, without the benefit of flow benches, so what is considered "very good" today might well have been state-of-the-art in 1963.

Anyway, the green curve in the first graph shows the simulation provides an excellent fit to engine 5000 (rounded up by ~25). For the green curve I used 60% for the flow efficiency. The overall h.p. predicted by the simulation is ~11% too high, which is outside the claimed 7% uncertainty of the program, so I still have some tweaking to do. As can be seen from the second graph the shape of the red curve with 65% flow efficiency is arguably a worse fit.

The red curve in the third graph for engine 6000 (rounded up by ~75), i.e. produced ~1000 engines later, is identical to the 65% in the first graph. Here the fit is excellent, and certainly better than the same 65% curve fit the data for the earlier engine. All parameters other than the flow efficiency are the same for all the graphs in this post.

The colors change their meaning in the fourth graph, where we jump back in production number to engine 3600 (rounded up by ~10) where red is now 60% and green is 57%. It's hard to decide if one fits better than the other, but certainly is consistent with the 57% being the better fit.

This is still very much a work in progress so these simulations, and the discussion of flow efficiency, aren't to be taken as final. But, it is highly suggestive that keeping all the parameters the same but allowing the flow efficiency to ooze higher over the production run of DBDs is consistent with the data as well as with what would be expected from the continuing development efforts of these engines.

Simulated h.p. at 7000 rpm:

55% 41.3
57% 41.8
60% 42.4
65% 43.8


Attached picture DBD_Clubman5000.jpg
Attached picture DBD_Clubman5000_2.jpg
Attached picture DBD_Clubman6000.jpg
Attached picture DBD_Clubman3600.jpg
As can be seen from the first graph I'm very close with the parameters for the DBD Clubman simulation. The fit is within 6.5% at the peak which is within the 7% accuracy claimed by the program. However, until I'm willing to remove the heads from my Gold Stars and flow test them and the exhaust systems there will remain a few uncertainties.

As I mentioned in an earlier post, absent flow measurements the program provides suggested choices for several components. Taking the inlet port and exhaust systems as examples of two components where I have no actual data (as opposed to, say, the carburetor where I've measured a GP on my flow bench):

Inlet Port Flow Efficiency:
55% Racing Heads
60% Very Good Racing Heads

Exhaust system CFM for 40 hp engine:
Calculated Exhaust System CFM Rating:
64 CFM Production Sporty
96 CFM Aftermarket
320 CFM Full Race

OK, what values for these two components should I use in the simulation? The problem is illustrated by the second graph that shows the calculated results assuming 60% and 83 CFM (green curve) and 55% and 96 CFM (red curve). As can be seen, there is essentially no difference between the two curves at the level of uncertainty of the BSA dyno data so it's impossible to use the best-fit to dyno data to choose between them.

Luckily, there are few such issues and their effects are not as bad as they could be. In the above case, since the exhaust system didn't change during the production run, if I get a good fit to a late DBD dyno curve I know that I only can change the inlet port efficiency when fitting an early DBD dyno curve. Although both values could be off somewhat from their true measured values, the trend won't be.

The program also has an "Analysis Report" feature that provides a four-page commentary on its findings, along with specific recommendations where and how gains could be made given the results it calculated. The BSA Race Shop would have found this very useful indeed. Just to highlight one point, it says "The Inertia tuning of this intake is tuned to 7009 RPM, which is close to your 'Desired HP Peak RPM' of 7000 RPM." So, BSA got that part right, at least on the DBD, although it means they got it wrong with the much shorter intakes of previous models.



p.s. to simulate earlier 500 cc engines I need the diameters of their valves:

______ intake dia. ____ ex. dia.
ZB ___
BB___
CB___
DB___

I have a feeling Gordo posted some of this but I don't have it in my folder and I can't find it on Britbike.



Attached picture DBD_Clubman6000_2.jpg
Attached picture DBD_Clubman6000_head_exhaust.jpg
Here are some valve dimensions from a 56 DB.

The intake, 65-2511, is 1.788 OD, with the seat within a few thousandths in from the edge.

The exhaust , 65-2512, is 1.532 OD, with the outer edge of the seat ~.030 in from the edge of the valve, as shrouding.

My head is on the engine, so I can't measure the throat diameter of the seats.

Hope this helps.

It would be interesting to know what silencers were fitted to the Production Sporty and after market bikes, and was the race a straight pipe, megaphone, etc. The difference in flow rate indicates that there was a marked decrease in back pressure, or a pulse tuning difference. ?????

JR
Originally Posted by Jerry Roy
Here are some valve dimensions from a 56 DB...
It would be interesting to know what silencers were fitted to the Production Sporty and after market bikes,...
Thanks very much for those dimensions.
At best the names in the program can only suggest values that might be appropriate. The only real way to know would be to hook up the items to the flow bench. I might measure an exhaust system at some point, but unless I inherit a spare head it's very unlikely I'll be making that measurement.

On the subject of heads and air flow, the first photograph shows the inlet tract of a 1928 Ariel (top) and 1963 BSA Gold Star (bottom), both 500cc. It's not as easy as you might think to accurately align a camera parallel to the inlet tracts and perpendicular to the mounting surfaces, and then get light into the cavities. I shot both from the same distance so they are the correct relative size in this photograph. Horsepower is directly proportional to air flow into the engine so you don't need a flow bench to see why the Ariel's smaller asthmatic inlet tract kept it to only about 20 h.p. while the Gold Star produced 40.

I adjusted the two inlet tracts to be the same diameter in the second photograph, showing that even then the Ariel's inlet would be more restrictive. Both engines are of the same basic design by the same person, Valentine Page, so these photographs show the results of 35 years of development work.


Attached picture ArielGoldStar.jpg
Attached picture ArielGoldStar_3.jpg
MM

Early ZB Intake tract 1.22, Intake port at valve 1.63, Valve head 1.72, (most likely original seats) Ex port at valve 1.558

Late ZB and BB Intake tract 1.20, Intake port at valve 1.60, Valve head 1.72, (replacement seats) Ex port at valve 1.56

CB Intake tract 1.162, Intake port at valve 1.66, Valve head 1.848, (replacement seats) EX port at valve 1.36

Gordo
Originally Posted by Gordo in Comox
CB ... Intake port at valve 1.66, Valve head 1.184,
The valve size must be a typo. It can't be 1.84, either, unless it was fitted with one from a DBD.

The inlet tract dimension for the ZBs and BBs also are suspect since they're quite a bit larger than the 1.09" of the carburetors listed for those bikes, as well as what you have for the later CB.

This is a problem when trying to extract original dimensions from "performance parts" that very possibly were modified sometime in the past 60 years.

Having this data isn't (yet) holding up my work because I decided I really do need to make flow bench measurements of the exhaust systems before proceeding. Removing this parameter as a variable will significantly improve the reliability of the simulation. I have a spare Catalina pipe as well so it's a matter of fabricating a jig for the flow bench.
MM: I have corrected the typo that you caught on above post. The CB inlet valve head is actually 1.848. Of course I have no history with this head and these are replacement valves. I have attached some photos of valves and head.

Valve seats

[Linked Image]

Valve heads

[Linked Image]

Gordo
MM: I went back to the early ZB and late ZB/BB heads. With a small steel ruler across the inlet tract (where carb bolts on ) I get the early ZB at 1 7/32 and two ZB/BB heads both at 1 3/16. These are close to the vernier readings I took earlier. In particular the the ZB/BB heads do not look to be modified at all and the are both the same.

Gordo
I haven't found any carburetor data for the earliest post-War Gold Stars, but the '53 Clubman used a 1-3/16" (1.188") and from 1954 the scramblers used 1-5/32" (1.156") (1-3/16" for a few years of the Catalina). So, inlet ports of ~1.20" seem reasonable.

Originally Posted by Gordo in Comox
I have no history with this head and these are replacement valves
The CB value you have looks suspiciously like a DBD valve, even more so since the DB size was smaller than the CB you quoted. Hopefully, others will jump in with additional measurements.

The program calls for the valve diameters so must make an internal correction for the estimated ID of the seat. Anyway, because of this I need the valve diameters. Otherwise I'll have to add my own estimated correction to the seat diameters after which the program will de-correct my correction with its own correction. Luckily, the ID of the inlet tract has only a small effect. The length, on the other hand, is important, but I have those values from a diagram in 'Goldie'.
Of course without history any mods are possible. My CB head appears to have the original inlet tract size. Given that there seems to only be one CB 500 casting, could the machining at the factory around the valve area have produced different heads for different uses?

Gordo
Hi,

Very interesting project!

Regarding the inlet track i think the data and input i read now, is “tricky” so to say.

Each inlet track “in the day” was different... man shaped end THE “part” wich did and does make the biggest difference regarding power output on these engines,
Flow testing a rather standard and original head from each type , Will make sence to get a “standard” to work with, but if you measure now the way people are doing now, (mainly 2 or 3 sizes in/of the whole inlet tracht) is far too easy in my opinion.. also valve shape in relation to the inlet trackt does make huge differences...
It is wat you can not of very difficult measure on a standard workbench what makes the biggest power difference on the inlet side..

On the other hand, exhaust is far more easy, shape of the port is not as significant as inlet (within limits) .. and you can calculate the exhaust pipe differences rather easy, diameter and length are the main parameters, shape (like straight pipe or megaphone or megaton (reverse cone on megaphone)) (as open systems are concerned) are only a way to shorten the Total physical length if you want to keep the same effective length, needed or wantend for that engine..

Just my innitial/first thoughts after reading the above..

Originally Posted by Gordo in Comox
could the machining at the factory around the valve area have produced different heads for different uses?
Harking back to an earlier conversation, they produced the BB scramblers in parallel with the CB Clubmans during the period of that short-lived model. But, the dyno sheets show that scrambles and touring CBs were made as well, so they must have given in to demand for the latest models for those purposes. However, the dyno sheets reveal that the same valves were used for Clubmans, Scrambles, and Touring CBs (65-1844 and 65-1845) so it appears they slapped the same head on all the models and, other than the cams, didn't try to optimize them for any purpose other than Clubman racing.

Looking again at the dyno sheets, there is nothing about the valves for the ZB, BB or DBD, but for all versions of the CB they're 65-1844 IN and 65-1845 EX, and for the DB Clubmans & Scrambles they're both 65-2511 IN and 65-2512 EX.

Originally Posted by Motolab
Each inlet track “in the day” was different... man shaped end THE “part” wich did and does make the biggest difference regarding power output on these engines,
Yes, but the hand shaping didn't affect the diameter by much, only the Flow Efficiency. When I say 'only' I don't mean to minimize the importance; it didn't require moving much metal around to have a significant effect on the h.p.

Originally Posted by Motolab
Flow testing a rather standard and original head from each type , Will make sence to get a “standard” to work with,
I very much would like to flow test a DBD head. It's just that I don't want the information badly enough to be willing to disassemble my 'Competition' to make the measurements. However, if someone has a DBD (and/or ZB, BB, CB, or DB) head gathering dust, that they know has an unmolested inlet tract, and they're willing to part with it for a few weeks, by all means let me know.
Originally Posted by Magnetoman


Originally Posted by Motolab
Each inlet track “in the day” was different... man shaped THE “part” wich did and does make the biggest difference regarding power output on these engines,
Yes, but the hand shaping didn't affect the diameter by much, only the Flow Efficiency. When I say 'only' I don't mean to minimize the importance; it didn't require moving much metal around to have a significant effect on the h.p.


We do both mean the same..... it is the form of the inlet wich makes the big difference, more than increasing the diameter.
Sorry I came very late to this discussion.

You seem to have gone a long way already but can I suggest you have a look at this engine simulation software. It is called EngMod4T. The programmer is an engineer in South Africa. The programme is based on and matures the G Blair simulation software that used to be marketed by SAE.

https://vannik.co.za/EngMod4T.htm


The fully professional version costs many $10,000.

https://www.optimum-power.com/Virtual%204-Stroke.htm


About 12 years ago I spent considerable time modeling and developing my Norton 500 Dominator bike for classic racing in New Zealand. I would iterate between the computer model and the dyno. At that ime I was using the old SAE version of the software and following the Blair text four stroke simulation.

Results were mixed.

I found very good curve shape prediction between the computer at dyno for modelling inlet tract changes. Especially lenght changes and peaks and troughs matched almost exactly computer to dyno.

I found very good shape and absolute value prediction results for a friends single cylinder Jawa speedway type engine.

On the other hand the computer did not model at all well the lower part of the rpm curve for the 500 twin. Megaphonitis was never predicted by the computer.i assume this was because it always assumed the carb would operate perfectly.

So I would say I used the software more to teach me about engine dynamics and pressure wave behaviour than using it for design - build - result type outcomes. Except for inlet tract modeling where the bike had clearly read the same book as the computer. :-)

For anyone interesting in seeing how these programmes work Lotus actually have free single cylinder basic simulation software on their website.

http://www.lesoft.co/
Originally Posted by johnm
You seem to have gone a long way already
Yes, it's too late to turn back now...

Originally Posted by johnm
I found very good curve shape prediction between the computer at dyno for modelling inlet tract changes.

I found very good shape and absolute value prediction results for a friends single cylinder Jawa speedway type engine.

On the other hand the computer did not model at all well the lower part of the rpm curve for the 500 twin.
My findings so far mirror yours. Although BSA dyno curves don't go below 4000 rpm for ZBs, and 5000 by the time we get to DBDs, so I have nothing to compare the simulations to for rpms lower than these.

Originally Posted by johnm
So I would say I used the software more to teach me about engine dynamics and pressure wave behaviour than using it for design - build - result type outcomes. Except for inlet tract modeling where the bike had clearly read the same book as the computer.
Well, since all the power is only what passes through the inlet tract, that's not so bad.

The program has taught me a lot about what matters and what doesn't. Once I got close with the DBD simulation I went through the inputs and changed them one at a time to see what effect each one has. For example, changing the exhaust port efficiency from 60% ("racing heads") to 70% ("excellent racing heads") has a barely perceptible effect on h.p. over the full range of the simulation from 3000 to 7000 rpm. So, if I were building a bike to race that tells me where not to spend any of my time. Intake runner length has a big effect in the midrange, which tells me I would want to explore longer intakes if building a scrambler.

I'm pretty sure all of this will pay off when "designing" a Gold Star for some particular purpose, e.g. spirited trail riding. Once the parameters are determined for a stock configuration, then "what-if" scenarios can be explored a lot easier than if having to actually swap parts and measure outcomes. The results based on the simulations only will be approximations, and one likely could do better given a large budget of money and time, but it appears to me that the simulations will take one close enough to the "optimum" that it would make most people happy. Unless they were racing and need to squeeze every last ounce of h.p. from the engine.

As an aside, you said you did your work 12 years ago. I wonder if any significant progress was made with simulation software in the meantime, or if the modeling available today is only incrementally better than it was back then.
Oh by the way MM, I think that I can speak for all the GS enthusiasts out there when I say how much we appreciate the work that you are doing. I have my cam collection lined up awaiting for the results of your work.

Gordo
Gordo,

Thanks very much for that sentiment.
I played hooky for a while today from what I should have been doing for long enough to fabricate a jig for testing the flow of various pipe and silencer (or not) combinations. I made it on a plate that I can either mount directly on the top of the flow bench, or at 90-degrees on the large plenum I use for testing carburetors. I only have the header pipe attached in the second photo but when the silencer is attached I may have to add a secondary support. That may determine that one orientation of the jig is better than the other.

I have two header pipes not currently attached to bikes (Clubman and aftermarket full-length Catalina) and five "silencers" (OEM twitter, short 'Competition'-type megaphone, aftermarket Burgess-type, aftermarket shorty, and 'none') so the flow of whatever I'm missing from these lists probably will be able to be estimated fairly well from the measurements of what I do have.

Attached picture SuperFlow_ExhaustJig_01.jpg
Attached picture SuperFlow_ExhaustJig_02.jpg

Quote "The program has taught me a lot about what matters and what doesn't. Once I got close with the DBD simulation I went through the inputs and changed them one at a time to see what effect each one has. For example, changing the exhaust port efficiency from 60% ("racing heads") to 70% ("excellent racing heads") has a barely perceptible effect on h.p. over the full range of the simulation from 3000 to 7000 rpm. So, if I were building a bike to race that tells me where not to spend any of my time. Intake runner length has a big effect in the midrange, which tells me I would want to explore longer intakes if building a scrambler.

I'm pretty sure all of this will pay off when "designing" a Gold Star for some particular purpose, e.g. spirited trail riding. Once the parameters are determined for a stock configuration, then "what-if" scenarios can be explored a lot easier than if having to actually swap parts and measure outcomes. The results based on the simulations only will be approximations, and one likely could do better given a large budget of money and time, but it appears to me that the simulations will take one close enough to the "optimum" that it would make most people happy. Unless they were racing and need to squeeze every last ounce of h.p. from the engine.

As an aside, you said you did your work 12 years ago. I wonder if any significant progress was made with simulation software in the meantime, or if the modeling available today is only incrementally better than it was back then.
[/quote]


That's what I was hoping to judge from your work actually. :-)

Intake runner length has a big effect in the midrange, which tells me I would want to explore longer intakes if building a scrambler.

Agree. That's what the computer told me and what happened in practice. In the specific case of Clubmans rules racing in NZ with mandated 4 speed gearboxes and tight circuits good midrange was exactly what won races.
Originally Posted by johnm
That's what I was hoping to judge from your work actually.
I haven't actively looked for it, but neither have I stumbled across it, but I don't know what the code is based on. Twenty years ago the cheap 'Desktype Dyno' program that came for free with a paperback book did a pretty good job.

To digress, many years ago at lunch one of my colleagues mentioned that custom golf clubs were a waste of money. I've never played golf but was interested in his comment. He pointed out that basically everyone's arms reach to the same point above ground so standard-length clubs fit everyone. That caused me to check this out and, it turns out, he was right. A tall person's shoulders are high above the ground, but their arms are long, so they reach down to a certain point. Similarly, short person, short arms, so they also reach to approximately the same point as the tall person's arms. The result is you could win a bet if you said you could predict how high above the ground the hands would be of the next person to walk into the room.

Back to engine simulations. Not knowing what's behind the code, I wonder if a similar principle to golf clubs is involved. That is, are all internal combustion engines basically the same so all you have to do is input a few simple factors (bore, stroke, valve configuration,...) in order for the program to use a look-up table to get an answer that is pretty close, after which it just tweaks that basic figure? Hmm....

Back to flow measurements. Take a look at the first photograph. Which pipe flows more air, the shorter 'Clubman' or the longer 'Catalina'? Well, you're wrong. The longer pipe actually flows 3.2% more air than the shorter one (I checked each pipe twice to be sure). Air typically doesn't behave the way you might think, and there's nothing like a flow bench to determine that the extra resistance due to the longer Catalina pipe is more than made up for by the sharper bends of the Clubman.

The simulation program uses exhaust flow rates measured at a pressure difference of 20.4" H20 so I've converted all my measurements to that value using conversion factors in the SuperFlow manual. In addition to the pipes I tested my OEM 'Twitter' silencer and two new aftermarket Burgess-type silencers whose internals are quite different. The results are:

Catalina pipe 201.6 CFM
Clubman header 195.4 CFM
Clubman + Twitter 165.4 CFM

Burgess-type #1 90.9 CFM
Burgess-type #2 184.4 CFM
OEM Twitter 186.5 CFM

These measurements are quite useful for the simulations since I now know the exhaust system is less restrictive than I had thought, which makes a significant difference in the calculations. The Twitter and #2 Burgess-type both allow the exhaust to pass straight through and only silence wayward sound waves that get lost and wander outside that straight path. The lower CFM of the Clubman + Twitter than the Catalina is largely due to the overall length being 11" longer and only somewhat due to the alleged silencing properties of the Twitter.

Attached picture SuperFlow_ExhaustJig_03.jpg
Attached picture SuperFlow_ExhaustJig_04.jpg
[quote

To digress, many years ago at lunch one of my colleagues mentioned that custom golf clubs were a waste of money. I've never played golf but was interested in his comment. He pointed out that basically everyone's arms reach to the same point above ground so standard-length clubs fit everyone. That caused me to check this out and, it turns out, he was right. A tall person's shoulders are high above the ground, but their arms are long, so they reach down to a certain point. Similarly, short person, short arms, so they also reach to approximately the same point as the tall person's arms. The result is you could win a bet if you said you could predict how high above the ground the hands would be of the next person to walk into the room.

Back to engine simulations. Not knowing what's behind the code, I wonder if a similar principle to golf clubs is involved. That is, are all internal combustion engines basically the same so all you have to do is input a few simple factors (bore, stroke, valve configuration,...) in order for the program to use a look-up table to get an answer that is pretty close, after which it just tweaks that basic figure? Hmm....

Hi

I understand your are a university physics professor and are therefore in a much better place than most of us to understand the maths.

Professor Gordon Blair of QUB was one of the pioneers of engine simulation.

https://daro.qub.ac.uk/pages/2016-rebrand/news/obits---all/obits-professor-gordon-blair

https://www.amazon.com/Design-Simulation-Stroke-Engines-R-186/dp/0768004403

Constrained by my rather dismal math ability (my MSc is in geology) I understand he did develop his programmes from fundamental physics and engineering calculation supported by experiments in the QUB labs. However Blair died a few years back so things should have moved on from there. I did look at some of the US programmes available years ago and they did seem to sit more in the look up table camp - and the lookup tables were built from dyno results on American V8 engines.

However despite what Blair said, I was always a little suspicious that my best matches always occurred with engines similar to the Matchless G50 engine that he uses for an example in the chapter on empirical engine simulation. ie for all the maths he still used experiments with the G50 to build his fudge factors ;-) The exhaust discussion on long pipes in that chapter did seem to have been read by my Norton as well !!.

A University Professor of engineering who designed racing motorcycle engines and pit crewed for his students at the Isle of Man should always be listened to very carefully !!



Gordon Blair was a very genial man and quiet man who really loved racing, especially in Ireland. His first success on a bike called the QUB, which was a four stroke. I can't remember what it was based on, perhaps the G50. He then had huge success by designing expansion chambers on the ubiquitous Yamaha two-strokes of the day, the 250cc and 350cc. These flow-tested engines were really fast, ridden by Queens student, Ray McCullough, and were the basis for what became a long-lasting relationship with Yamaha, and Blair's work being hailed all over the world.

Several years later, MMan and I had the pleasure of knowing Nobby Clark, who worked on some of those Yamaha teams, and shared some of his technical insights regarding flowing the two-strokes, this time by raising the ports.

Fun stuff.
Originally Posted by johnm
Professor Gordon Blair of QUB was one of the pioneers of engine simulation.
Indeed he was. Most of his work was on 2-strokes but he did a lot of work on 4-strokes as well. And he wasn't just a pioneer in the sense of having done important work long ago. He continued until his death at a youthful 73 less than ten years ago.

Originally Posted by johnm
I did look at some of the US programmes available years ago and they did seem to sit more in the look up table camp - and the lookup tables were built from dyno results on American V8 engines.
No matter how sophisticated the underlying models might be, the capabilities of most PC-based programs have to be hobbled to work with the PCs available at the time they are released. Since the computing power has increased by at least 100x in the past decade, a state-of-the-art program written in 2009 would be significantly less powerful than one written today. However, that's a general statement. A given program may not have been all that advanced when it was released, and may not have been updated much or at all since then. Or, a program may have been able to take full advantage of the models that existed at the time and new modeling might not have added much since then.

Anyway, the manual for the Engine Analyzer Plus program I'm using has a 2010 copyright date. However, I don't know if there's a newer and more powerful program for a similar price. In any case, the program seems to have inputs for all the relevant factors that should go into a proper model and it is producing quite credible results that are only limited by estimates I have to make in the absence of certain specific data. However, that took a step forward yesterday with the flow data on exhaust systems, and shortly will take a leap forward when I make flow measurements on the Catalina head NYBSAGUY is about to send.

Originally Posted by johnm
A University Professor ... should always be listened to very carefully !!
I couldn't agree more...
I've been keeping quiet, but by invoking the name of Gordon Blair you may have entered a rabbit hole from which you can never return.
Steady state gas flow is important, but as Walter Kaaden and Gordon Blair found, the pressure wave characteristics of the pipe have a significant effect on the engine's power peak and torque spread. They also found that once you're hooked, it's impossible to shake the addiction...
I was thinking the exact same things the last few days, regarding the pressure wave effect. This effect is very significant on 4 stroke’s indeed...and within limits far more important than “more” flow. Phil irving did explain the effect and how you can use it (and what happens when wrong) in his master piece for the (home) tuner ,” tuning for speed” published in the ‘40’s, this book contains also some goldstar specific info on other subjects..
Originally Posted by Shane in Oz
, but as Walter Kaaden and Gordon Blair found, ...
Originally Posted by Motolab
Phil irving did explain the effect and how you can use it
OK, you guys, Irving's book was published 70 years ago(!), Kaaden's groundbreaking work on expansion chambers was done over 60 years ago, and Blair's further development of exhausts had pretty much ended as of 40 years ago. It seems like a reasonable assumption that simulation programs that have been around a long time, and periodically updated, have incorporated what's right with early work, weeded out what's wrong, and included developments of the most recent four decades.
Originally Posted by Magnetoman
OK, you guys, Irving's book was published 70 years ago(!), Kaaden's groundbreaking work on expansion chambers was done over 60 years ago, and Blair's further development of exhausts had pretty much ended as of 40 years ago. It seems like a reasonable assumption that simulation programs that have been around a long time, and periodically updated, have incorporated what's right with early work, weeded out what's wrong, and included developments of the most recent four decades.
That will be the add-on exhaust tuning package.
What parameters are available in the simulation package(s) for exhaust systems?
Originally Posted by Magnetoman
It seems like a reasonable assumption that simulation programs that have been around a long time, and periodically updated, have incorporated what's right with early work, weeded out what's wrong, and included developments of the most recent four decades.

I hope so, and is seems a reasonable assumption, ;-)
are 2 or 4 valves a variables in this program? What we see here on de dyno, for instance, that with the same engine layout, in stroke and engine displacement but with different head/valve layout (2 valve or 4 valve) an engine asks for different flow rates of the exhaust, (4 valve engines/heads are needing more flow) but ofcourse the engine/exhaust system needs the same pressure wave characteristics... to get a “flat” as possible torq curve.. (within the limits of what is possible with these variables and exhaust systems)
Originally Posted by Shane in Oz
]That will be the add-on exhaust tuning package.
Spoken like someone who understands commercial software... The company I bought from has four levels of packages, priced at $129, $199 (the version I bought), $499 and $749. Needless to say, the more expensive packages have a lot more inputs (although most of the additional capabilities of the most expensive one seem to be aimed at turbochargers and fuel injection).

Originally Posted by Shane in Oz
What parameters are available in the simulation package(s) for exhaust systems?
There are two headers that seem applicable to a single-cylinder engine: individual tubes that connect at a collector, or individual tubes. For a single-cylinder engine both should give the same results if the collector has the same dia. as the pipe and the overall lengths are the same. Beyond that choice, inputs are dia., pipe length, collector length (if any), and flow efficiency. If there is a silencer, another input is its CFM. In most cases (e.g. silencer CFM) the program suggests values to use if you don't have the measurements.

Originally Posted by Motolab
are 2 or 4 valves a variables in this program? ...
Yes, for the head there are ten chamber types (hemi, wedge, sidevalve, ...), and intake layouts of 1 valve or 2 valves, with the latter having combined or separate ports. Valve dia., average port dia., port length and flow efficiency are the other inputs for the inlet.

But, keep in mind I didn't buy this program to try to build an engine to win the IoM or set a land speed record. I bought it to try to accurately model the output of Gold Star engines as they left the factory 60 or so years ago in order to then run 'what-if' simulations with different cams, carburetors, etc. For this, the biggest limitation I can see thus far is the inability to enter something like the behavior of the Clubman's semi-reverse-cone megaphone. The program handles the effect of the length of a pipe, but the additional strength of the pulses due to the megaphone is an uncertainty. However, the Scrambles data with straight pipes allows me to gain confidence in the simulations.

I expect when the Catalina head arrives from NYBSAGUY the flow bench data from it will significantly reduce remaining uncertainties, even for the Clubman. Rather than me having to guess at the inlet "Flow Efficiency" based on descriptions like "Racing Head," "Good Racing Head," etc. the program lets me enter flow measurements at a minimum of four, and max. of eight, valve lifts from which it calculates the Flow Efficiency. This parameter has a large effect on both the slope and max. h.p. so I'm very much looking forward to having the data to enter since it then will reduce the remaining uncertainty in cam/lifter parameters. At that point, whatever parameters I have to enter to fit the dyno data shouldn't have much uncertainty in them.


MM: I have been going through your old thread on 'part numbers for heads' and I am a bit confused about the Catalina. For clarification were there both DB and DBD Catalina engines? The thread implies there were both types. How are the Catalina engines stamped?

Gordo
Gordo,

Yes, there were both DB and DBD Catalinas. An undated (but obviously 1957) supplement from BSA East Coast lists two heads for 1955-56 DB Models: 65-2467 for the 'Cylinder head' and 65-2467 for the 'Cylinder head (Catalina Scrambler)'. The next page of the same supplement for 1956-57 DBD Models only shows one head: 65-640. I don't remember now where I got the information (or misinformation), but I recall that Catalinas continued with DB heads for some time even though they where stamped 'DBD'.(*) Catalina engines had the extra code 'S' under the engine number. A possible source of confusion is that if an engine is stamped with a 'C' it's a Competition, not a Catalina.

(*)I've now found despatch information that confirms all DBD34 Catalinas were in Catalina CB32C frames (first of which was despatched 12 November 1958), whereas DB34 Catalinas were in CB32 frames . However, this doesn't address whether or not early DBD Catalinas might have had DB heads despite the DBD stamped on the engine.
For sure specifics are hard to come by some 60 plus years after the fact. The BMS book chart shows the first Catalina in 1959 (model year?) as a DBD in a CB32C frame. Of course what would the UK researcher know about a US model?

Thanks

Gordo
Originally Posted by Gordo in Comox
The BMS book chart shows the first Catalina in 1959 (model year?) as a DBD in a CB32C frame.
The 1956 East Coast sales catalog has a Catalina in it, three years before BMS was aware. Not for the only time was a British author oblivious of export-only models like the Catalina or Spitfire.

Attached picture Catalina1956_East.jpg
I should have looked at my copy of 'The Gold Star Buyer's Companion' before I commented. It seems to have better info.

Gordo
Originally Posted by Gordo in Comox
'The Gold Star Buyer's Companion' ... seems to have better info.
I'd say that much more so than any other motorcycle book, information was carefully vetted before it went into the 'Buyer's Companion'. Even if certain information is "common knowledge," but if it couldn't be verified, it's not in the book. It's always possible mistakes or errors have still managed to slip through, but they should be rare exceptions.
MM: I think the real issue is what left the factory and what was actually sold in the US dealerships. Did the dealers make standard Scramblers into Catalinas by sticking on a decal and using the name in the adverts even before the factory recognized the unique model? The BMS type list could be what the factory thought they were shipping to the Colonies.

I will search through the Goldie magazines to see what Ian has published about the Catalina and the CB32C frames according to his records. It could be the factory catching up to reality.

Gordo
Originally Posted by Gordo in Comox
Did the dealers make standard Scramblers into Catalinas by sticking on a decal and using the name in the adverts even before the factory recognized the unique model?
Gordo,

Ian Jackson found the DB34 bikes that left the factory starting in 1956 are in the despatch records as 'Catalina' so it was a genuine factory model, not "dealer-manufactured" with a decal. However, what I believe is currently unknown information is at what point the 'S' stamp was added below the engine number, and if it only applied to Catalinas or was also on "ordinary" Scrambles models available to the rest of the world.
The engine simulation project made a huge step forward today with the arrival of a Catalina head on loan from NYBSAGUY. The photograph shows it sitting on a 500 cc cylinder that is bolted to the top of my flow bench.

Scrambles models used 65-2446 cams for both the inlet and exhaust, having maximum lift 0.404". But, since the reason for doing these simulations in the first place is to be able to answer 'what-if' questions, I'll measure the inlet lift to 0.442" in case anyone ever feels the urge to install a Clubman cam in their Catalina but wonders what effect that might have.

I've started making the necessary valve opening fixture to bolt to the top of the head that will press the valves open in increments measured by a dial indicator. Maybe the fabrication will be more difficult than I expect, in which case I'll come to understand why the prices of such fixtures start at over $300, with many versions selling at more than double that.

Attached picture FlowBench_Catalina.jpg

And, as a quick PS..

Lest you think I prepped this head beautifully for MMan's experiments, full disclosure requires me to tell you that I sent it first to Phil Pearson, who breathed on it quite beautifully. So beautiful that I haven't been able to bring myself to assemble the engine. Just as well, as it turns out.

Now, let if flow, let it flow, let it flow...
Originally Posted by Magnetoman
[

But, keep in mind I didn't buy this program to try to build an engine to win the IoM or set a land speed record. I bought it to try to accurately model the output of Gold Star engines as they left the factory 60 or so years ago in order to then run 'what-if' simulations with different cams, carburetors, etc. For this, the biggest limitation I can see thus far is the inability to enter something like the behavior of the Clubman's semi-reverse-cone megaphone. The program handles the effect of the length of a pipe, but the additional strength of the pulses due to the megaphone is an uncertainty. However, the Scrambles data with straight pipes allows me to gain confidence in the simulations.



The software I mentioned does have the options to define complex exhausts including reverse cone megaphones.

Going back to Blair, the top end commercial programmes and computer performance. i read a paper about ten years ago where the modelers were varying 3 parameters at a time. The output was a contour map in three dimensions. Run times were 24 hours plus.

When modelling exhaust systems for a twin project for a friend introducing a balance pipe between two exhaust pipes took the run times up to 5 hours compared to 30 mins for single pipes. The optimal system ended up looking like a BMW airhead exhaust system. Not a big surprise perhaps !

I imagine a good modern PC would do the job in a few minutes
Originally Posted by johnm
Going back to Blair, the top end commercial programmes and computer performance
It would be very easy for someone like me to get sucked down that rabbit hole (as if I'm not already down another rabbit hole, albeit one that -- I hope -- has a way out of it before too much longer).

Although it's unlikely I'll ever want to flow test an exhaust port, it didn't take all that much more time to make a "universal" Gold Star valve opening jig than it would have to make one for the intake only. However, the intake valve is at an angle of 33°45' and the exhaust is slightly different at 33° so I "optimized" the jig for the intake.

Despite what I wrote in the previous paragraph, the first photograph shows me milling the "riser" for the jig at an angle 33°. Actually, the angle of this piece isn't critical and the easiest way to make it was in the vise using 30°+2°+1° angle blocks. After fabricating the base and welding the riser pieces I then clamped it on an adjustable table set to ~33°45' to drill and tap the holes for the adjusting bolt and dial indicator. This placed the adjusting bolt precisely co-axial with the intake valve and the indicator precisely parallel with that axis. The slots in the base allow the jig to be dropped over either the intake or the exhaust studs, whose patterns are mirror images of each other.

The final images show two views of the jig as mounted to the head. Three features aren't apparent in the photographs. One is that, although the indicator hangs over the end of the tubing, there is a washer between the indicator and the jig to have its mounting point as close as possible to the lever arm of the adjusting screw. Because of this, even if the tubing bends under the load the indicator will be displaced by (approximately) the same amount as the adjusting screw. Another is I TIG-brazed silicon-bronze to the tip of the adjusting screw so a relatively soft material (Rockwell C hardness <2) is in contact with the end of the valve to avoid any possibility of abrasion. Finally, I Tig-brazed a nut to the underside of the arm because the tubing wall thickness only allowed for a couple of threads and they might not have supported the full force of the valve spring.

I had to end the day early because of other commitments, but I did do a quick check of the apparatus before I finished. Everything seems to be working well, so tomorrow I flow test.

Attached picture ValveOpener01.jpg
Attached picture ValveOpener02.jpg
Attached picture ValveOpener03.jpg
Attached picture ValveOpener04.jpg
Attached picture ValveOpener05.jpg
Thanks to having NYBSAGUY's Catalina head on the flow bench I made significant progress with the Engine Analyzer software today. And the day isn't done yet. However, things always seem to become more complicated when you get into the details and this is no exception.

The software has separate entries for the flow of the carburetor and of the inlet tract, which perhaps suggests I shouldn't install the carburetor for the flow testing because the program wouldn't be able to distinguish between the fundamental restriction of the inlet port and that of the carburetor when calculating the efficiency. However, the SuperFlow manual says "it is strongly recommended" to install an inlet guide which they suggest should be "about one port width in thickness" (i.e. ~1.2") and "generously radiused on the inside all the way to the head."

In any case, since the purpose of this flow testing isn't so much to determine the absolute flow rate, but rather to determine the inlet port "Flow Efficiency," it's pretty clear that I'll need to make a radiused inlet guide to send the air smoothly on its way into the head. However, I couldn't wait to make that guide before running a test. That is, a test, test.

Making a long story short (because it will change), despite not yet having an inlet guide I ran the flow tests up to full lift for a 65-2446 inlet cam. As a reminder, the program gives the following efficiencies to use if flow data isn't available:

55% racing heads
57% good racing heads
60% very good racing heads
65% excellent racing heads

If flow data is available the program allows entry of up to 8 lifts, calculating the flow efficiency at each lift. What I found is for lifts of ~0.2" and less the program calculates values for the Catalina head of ~58%, but then decreases to ~54% at 0.3" and 48% at full lift of ~0.4". Although it remains to be seen, I suspect the inefficiency at high flow rates might be due to turbulence due to the lack of that radiused inlet guide that I'll now be fabricating.

Anyway, at this point my preliminary finding is a 60-year old Catalina head seems to be a "good racing head" even by 2019 standards.
I had a short length of 4½"-dia Teflon rod that was perfect for making the tapered inlet. Since 3-angle valve jobs have been researched extensively for maximizing flow I decided I'd use those values. After boring the hole the same ID as the inlet to the port, I then cut 15°. 30° and 45° tapers. To avoid having the mounting studs project into the flow I carefully measured their lengths and then drilled to just those depths, relying on a tight slip fit over the studs to hold it in place. This mounting scheme worked very well as can be seen from the second and third photographs, with the Teflon pushed just slightly into the taper at the studs. With the tapered inlet in place, a quick measurement showed that near full lift the head flowed ~6% more than the bare head so having it does make a difference.

After entering the results into the program I then read the manual to find it bases its calculations only on the flow results at the value of lift corresponding to the ratio of lift to valve diameter = 1/4 (i.e. L/D=0.25), noting that once that point is reached the area of the inlet port rather than the area around the valve is what limits the flow. Since the inlet valve is 1.85" that's a lift of 0.46". This means all the time I spent measuring the flow at lower lifts was wasted, at least as far as the program is concerned, and I only needed to have measured the flow at a lift of 0.46" (I stopped at 0.404"). Oh well, live and learn. Actually, my "iterative" process is deliberate since by quickly running through the entire set of measurements and calculations I learn what I need to spend time on, and what requires less attention.

L/D explains why the program helpfully asks me if I've made a mistake with the valve diameter because it appears to be too large. Also, the lift of 0.46" for L/D=0.25 is close to the 0.442" lift of the Clubman cam (0.404" for the Catalina), which is consistent with the valves having been optimized for the Clubman engine and simply reused on the Catalina without further optimization for the smaller inlet tract and lower max. rpm (6500 vs. 7000).

Attached picture SuperFlow_Inlet01.jpg
Attached picture SuperFlow_Inlet02.jpg
Attached picture Superflow_Inlet03.jpg
The problem with having data is it ties your hands. Unfortunately, now having good flow data on NYBSAGUY's Catalina head I'll have to spend more time with the program to get back to where I was before I had the data.

Originally Posted by Magnetoman
...bases its calculations only on the flow results at the value of lift corresponding to the ratio of lift to valve diameter = 1/4 (i.e. L/D=0.25),
The diameter of the Catalina's inlet valve is 1.85" so I measured the flow at values of the lift around 0.25x1.85"=0.462". Plugging these values into the program gave an inlet flow efficiency of only 47.8+/-0.2% at L/D=0.25. Given what I wrote before about "good, "very good," etc. racing heads, this seemed quite low. It falls between the flows of modern "as cast aftermarket heads" and "ported aftermarket heads."

For a while I thought I had done something wrong but, after carefully redoing the measurements, I found the attached table in the manual (yellow highlights added by me) indicating ~48% actually was very good for an engine designed in the mid-1950s. So, having this data, and since the data makes sense, my hands are tied.

I'm joking, of course, since the more data I have for the program, the fewer adjustable parameters (i.e. uncertainties) there will be. This only will make the final simulation that much more robust.

On the subject of additional data, I already have the air cleaner assembly off my Catalina waiting for its turn on the flow bench. But, Gordo and I only have one dyno curve for a "Scrambles" DBD, not a Catalina, so that's going to be a limitation until it's solved.

p.s. The SuperFlow manual gives a formula for the maximum power for a "well-tuned racing engine" that has "the maximum compression, the right cam, and a tuned exhaust system" that is calculated from the measured flow at maximum valve lift. Assuming my friend's Catalina had a Clubman cam installed (i.e. with greater lift than the Scrambles cam), higher compression piston, and a tuned exhaust rather than a straight pipe, this formula estimates it should produce 50.5 h.p. That's 1/3 more h.p. than a Catalina in stock configuration was measured to produce on the dyno so the estimate from the formula is too optimistic, but it does indicate my friend's Catalina head is in excellent condition.


Attached picture EngineAnalyzer_FlowEfficiencies.jpg
That damn NYBSAGUY just cost me $40. If he hadn't loaned me his Catalina head to test I wouldn't know the inlet tract flow efficiency was so low (by 2019 standards), so I wouldn't now be facing the problem that the simulation runs into a wall at ~5500 rpm. I've checked for obvious, and non-obvious, mistakes (e.g. converting flow measured at one pressure to the figure needed by the program at
another pressure), but the h.p. rises nicely to ~5500 rpm and then turns over. So, I had no choice but to have the ~300 page manual printed. And, worse than that, I now have to carefully read it in the hopes of finding what is going wrong. Damn you NYBSAGUY!
<<Damn you NYBSAGUY!>>

Ha! This is only the beginning. I'm going to cost you a whole lot more by the time this is over..
My wallet took a hit, but as a result I'm moving forward again.

The black lines are traces of the dyno curves so I don't have to make the simulation partially transparent to see them.

Attached picture DBD_Scrambles67xx_sim001.jpg
It's working then..
Originally Posted by Kerry W
It's working then..
I'd say it's working very well indeed.
Hi

I'm new to the forum and only quickly run through the simulation work you have carried out. As a Goldie racer of some years I've also taken a "modern" approach to engine development by purchasing a copy of the Vannik 4t programme. It is a somewhat more powerful programme using the development of Prof Blair. Not only has Cornelius been a great help but also his Beta tester.
What you will find as you progress in making small alterations is the outcome will not match the popular misconceptions. No1 being more flow=more power. Is your software able to show pressure wave in the form of a graph at all the tested rpm. This is invaluable. It highlights the truth of what makes the engine, and that is pressure differential.
Keep up the good work. With careful selection of standard bsa parts and exhaust/inlet dimensions a 20% increase in power with the 500 is easily found.
Originally Posted by Elfin jnr
I've also taken a "modern" approach to engine development ... popular misconceptions. No1 being more flow=more power. Is your software able to show pressure wave in the form of a graph at all the tested rpm.
Thanks very much for your post. My goal is perhaps different than yours, in that I "only" want to determine the effects of substitution of various stock BSA components on otherwise-stock engines. I'm not trying to investigate the (more complicated) effects of modifying the inlet port, installing a smaller/larger exhaust valve, a second spark plug, etc. The questions I hope to answer are of the type, what would be the effect on the h.p. and torque vs. rpm of, say, installing a Clubman inlet cam in a Scrambler, or using an 8:1 piston instead of a 10:1?

My flow bench measurements aren't to increase h.p. but simply to characterize the flow of standard components. On this topic, don't tell NYBSAGUY who loaned me the Catalina head, but out of curiosity a week ago I ordered silicone casting rubber that I will use to make a mold of the inlet tract. If I'm unable to remove the slug of silicone from the tract I expect it might reduce the h.p. of his engine somewhat, which is why I don't want him to know I'll be doing this.

My simulation work has been on a temporary hold while I catch up on another project that, unfortunately, has actual milestones and deadlines. However, I hope to get back to it within a few more days. So many interesting things to do, so little time...
Originally Posted by Elfin jnr
exhaust/inlet dimensions a 20% increase in power with the 500 is easily found.


Originally Posted by Magnetoman
[quote=Elfin jnr] effects of modifying the inlet port, installing a smaller/larger exhaust valve


First..MM i understand what you want.. BUT Elfin nr does not mean necessarily that dimensions (valve dia. and modifying ports) .. only length and diameter of both inlet (carb incl manifold etc) and exhaust pipe alone can have such an effect on power.. so race cam in clubman with specific inlet length and specific exhaust length, behaves different in a scrambler with same basic engine/volume and compression ratio same race cam but with other length carb (incl air filter)/ inlet tracks and exhaust length (and diam.)

I presume you know this, so I am very curious how the “end” and result list, will show up ;-)

Evening, all..

I have not been following this thread, because I am way to busy on other stuff.

But I did send MMan my head, for experimentation purposes only. And now I hear he is going to create a silicon mould of my inlet. Well, I say.. I think you might have told me. But it begs the question, Which inlet?
Motolab is correct in what he says. The exhaust fitted to the 350/500 is generic and made to fit the bike/frame, as is the carb. By simulating the engine with what mechanicals you have, you are now in the enviable position to read the pressure traces and design an induction and exhaust system to create the best case scenario. What I like to call equilibrium. Ie at the point of the inlet valve opening Inlet pressure needs to be greater than cylinder pressure. Like wise the exhaust pressure, at the manifold also needs to be below that of the Inlet. As the cylinder fills and pressure in there goes up, the inlet port pressure should follow as close and for as long as you can possibly get it before the Inlet valve closes. You will then see inlet port pressure "bounce" as the superposition wave goes back and forth. Lengthening the inlet will reduce the number of bounces. The fewer bounces the less that pressure point is eroded.
Get these timings and others not mentioned working in harmony and the benefit far greater than any flow bench test can ever possibly generate.

On the software side, I need the ability to convert cam profile results at the valve. This is due to using modified Rocker arms of various lengths. Does any of the software you have viewed given this kind of usability?
Originally Posted by Elfin jnr
using modified Rocker arms of various lengths. Does any of the software you have viewed given this kind of usability?
I don't remember what I found when I was looking at the various programs on the market, but ' Engine Analyzer Plus' by Performance Trends that I'm using allows ratios up to at least 1.8:1.

I've hit another roadblock thanks to Microsoft. It did some sort of major update to Windows 10 last week and as a result my home office computer no longer recognizes any printer (sadly, it's not a simple issue of reinstalling the printer). It also changed various settings for other programs (I'm still discovering new issues). My work-around for the printer is to transfer files to my laptop and print from it, but this is quite a headache. My laptop also got the same upgrade but is still able to print, although other settings were altered and at least one program I use now won't open and diagnostics says it's incompatible with Windows. Not being able to print the 'Engine Analyzer' results makes comparing the results of changes essentially impossible. Hope springs eternal that I'll get it working again before too much longer.
Originally Posted by Magnetoman
... update to Windows 10 last week and as a result my home office computer no longer recognizes any printer ... Hope springs eternal that I'll get it working again before too much longer.
I wrote the above two months ago. For those interested in these simulations who might have given up hope since then, I think I now have a "permanent" fix to the printer problem. I got the computer to recognize the printer for a few weeks since I wrote the above, but another Windows update severed the connection again a month ago and since then I've only been able to print by transferring files to my laptop. Anyway, fingers crossed that this new fix is more robust than the last one so I can fire up the simulation effort again.
I share your pain MM.

My business (a very large Engineering company) has recently upgraded everyones laptop to the latest business standard item and the OS to Windows 10. I can honestly say that it is the worst OS I have had the misfortune to have to suffer on a daily basis. This is not just my opinion but the universal opinion of everyone in my office.

I sincerely hope that your printer problems are the only issues that you experience. At least you can have a go at sorting it yourself rather than have to rely on an IT Hell Desk due to the fact that everything has been tamper proofed.

John

My friends in architecture and design (including, I am sure, MM's architect daughter, though I haven't asked her) also share this pain. They are split between Macs and PCs, but the design work is largely done on PCs. And they are having a nightmare since the recent upgrades, both to the OS and to the various drafting, modeling and draughting apps that they use.

The lesson is, and perhaps this should be written as a scientific principle: Things don't always necessarily get better.
Avoiding actual work by escaping to work on my trailer is winding down, so I've turned back to engine simulations as my principle outlet for avoidance.

Since I last worked on this I received one more dyno sheet, which broke the back of my notebook and I had to bring a second one into the operation. All the ZB-DB sheets are now in one book and I moved all the DBD to the second one. In both cases, I have each 'series' (e.g. ZB) and each configuration (e.g. Clubman) separate and with the sheets in increasing order of engine number to make it easier to spot differences or changes.

In moving the DBD sheets to the new notebook I noticed something I hadn't before (or, that I had, but since forgotten). All six of the Clubman DBD dyno data run from 5000 through 7000 rpm, and two of the three Scrambles DBD data run from 4000 through 6500 rpm. This makes sense in terms of the intended use of the machines. However, the third Scrambles sheet, which has the lowest engine number and further is a Catalina, runs from 5000 through 7000 rpm.

The pre-printed sheets only have 'Scrambles' and 'Clubman's' on them, with one of them crossed out as appropriate. This is also the case for the third "7000 rpm" Scrambles sheet which I know to be for a Catalina, although there is no mention of that on the sheet. One of the "6500 rpm" Scrambles sheets has a different format and lists the cams, which are 65-2446 for both the inlet and exhaust. This is what the BSA literature lists as correct for a Scrambles Gold Star. None of the Clubman's sheets lists the cams, but the literature gives 65-2442 inlet and 65-2446 for the exhaust of those machines. Different inlet cams, different rpm ranges.

OK, back to the "7000 rpm" Catalina. I only have the single sheet that I know is for a Catalina, but does the fact the data for it runs to 7000 rpm mean it was built with Clubman's cams? It happens that this bike is a fairly early Catalina (engine no. 43xx), tested in June 1959, so a further question is that even if the early ones came with Clubman's cams, did this practice continue for later ones?

The more information I gather, the more questions that are raised.

Very interesting.

My Catalina is a 59, with engine #43**. But it came to me with different cams, the 65-2446 exhaust, the 65-2442 inlet.. Of course I don't know if that is how it was shipped. The BSAOC told me that my bike was shipped with 65-2446 cams, but I don't think they had actually looked at the dispatch records for that bike.
Originally Posted by NYBSAGUY
Very interesting.
My Catalina is a 59, with engine #43**. But it came to me with different cams, the 65-2446 exhaust, the 65-2442 inlet.. Of course I don't know if that is how it was shipped...
Very interesting, indeed. That Catalina dyno curve I referred to is the one from your bike. I'd forgotten what cams you said came with it but, in light of this, I think there's a very good chance it came from the factory with the cams that you now have, i.e. Clubman's cams. The person at the BSAOC who told you it was shipped with a pair of -2446 was (incorrectly) assuming that was the case because the dyno data was marked "Scrambles." This certainly isn't the first time the configuration of a U.S.-only bike befuddled a Brit.

OK, we've established with pretty high certainty that your #43xx 1959 Catalina came from the factory with Clubman's cams. Irrespective of the intended configuration all Gold Star engines were stamped sequentially. The first Catalina in a CB32C frame was engine #377x in frame -101 and, without checking with you, I know from the date n the dyno sheet that your frame would have been ~-300, i.e. it was within roughly the first 200 Catalinas with CB32C frames that were made. Questions this raises include:

-- Were any or all of the pre-CB32C Catalinas shipped with Clubman's cams?
-- Were all of the initial ~200 (or more) 1959 CB32C Catalinas shipped with Clubman's cams?
-- If Clubman's cams were used for a period, at what point (if ever) did they stop being used?

The rabbit hole continues to get deeper.

For those who are interested in what difference it might make to put Clubman's cams in a Catalina head, thanks to my age-appropriate TI59 programmable calculator, we now have the experimental, not simulated, answer:

[Linked Image]

The black curves are from the sheet that explicitly lists the -2446 pair of cams and the green overlay is the h.p. curve from the 1959 Catalina whose dyno curve covers the 5000-7000 rpm range normally seen on Clubmans machines. However, it's not so simple, because the black Scrambles curve comes from an engine 2300 higher in number and progress was made in increasing the h.p. throughout the time of production. That is, a Catalina early in the production cycle with Clubmans cams produced more h.p. than one made much later in the production cycle with Scrambles cams.

While you're thinking about the above graph, how about a, ahem, head-to-head comparison of an actual Clubman and that same early Catalina? The next graph shows just such a comparison for a Clubman engine only 228 higher in number than that early Catalina. I'll leave you to ponder this without making further comment (because I don't know what comment to make)

[Linked Image]


Attached picture DBD_Scrambles_43xx_Scrambles67xx.jpg
Attached picture DBD_Scrambles_43xx_Clubman46xx.jpg

It gets better and better. You are quite right about my frame, which is number 3**.

What the above graphs demonstrate is the engine's ability to produce oodles of power at high RPMs. What was demonstrated to me on our recent ride, where we rode all three of your bikes, including a Clubman and the Catalina, is that I will never rev these engines anywhere near their maximum power curve.
For a Catalina to have more h.p. than a Clubman doesn't seem to make sense. But, I only had the data from one Catalina for comparison. Or did I? I actually had written in pencil "Catalina" on another of the three Scrambles sheets, but I erased it yesterday because I couldn't remember where that information came from. But, I should have trusted myself more because I am very careful with information like this to only to write down things I know, not what I might guess. Anyway, in the light of a new day I checked further and "discovered" that second sheet is from my own Catalina. Sigh...

Anyway, the engine no. on mine is nearly 2200 higher than on NYBSAGUY's so the next graph shows an early-late comparison of the h.p. developed by Catalinas:

[Linked Image]

The raw data shows my Catalina makes an extra ~1 h.p. at 6500 rpm but correcting for the different temperature and pressure of the two measurements (but assuming 30% humidity in both cases, which isn't something on the sheets) the difference increases to 1.9 h.p. for the later machine.

So, we have two measurements made 2 yr. 4 mo. apart on Catalina engines that agree reasonably well with each other (38.7 & 39.9 hp @6500 rpm), both producing significantly more hp than one known to have Scrambles cams (37.5 hp @6500 rpm). The Scrambles engine no. is only 150 higher than that of my Catalina so an "age-corrected" comparison is 37.5 hp Scrambles vs. 39.9 hp Catalina. At about the same time as my Catalina was made a Clubman (~740 engines earlier) produced 38.9 hp @6500 rpm (40.0 @7000) and a Competition (~540 engines later) produced 40.2 hp @6500 rpm (41.7 @ 7000).

OK, that's a lot of numbers to digest. To summarize, although it would be great to have a few more data sheets on Catalinas and home-market Scrambles to check, the data I do have indicates the U.S. got 'scramblers' with significantly more hp than the Scrambles machines sold in the UK.

However, irrespective of the cams that might have been used, I'm having a hard time reconciling the fact the dyno sheets show Catalinas produced more hp than Clubmans. This, despite the head having a smaller inlet tract and using a Monobloc carburetor. If a Catalina engine truly did produce more hp than a Clubman, why did BSA continue to build machines with the "old" Clubman specification instead of adopting the seemingly-better Catalina specification? On the face of it, this makes no sense to me. Could BSA have faked the Catalina dyno data by adding a couple of h.p. to make Alzina think he was getting something better than the home-market guys were?

Attached picture DBD_Catalina_43xx_67xx.jpg
MM: In the literature there are comments about engines being sent back due to poor performance. As the hp went up over the years for any given engine model what would have been the hp number that would allow an engine to pass the test run. Is there any knowledge of such a number?

Gordo
Originally Posted by Gordo in Comox
Is there any knowledge of such a number?
I haven't seen any list giving those figures but a couple of early test sheets provide some indirect evidence.

On 11 June 1953 a BB "Racing" engine with "Special" valve springs was tested twice, once giving 23.2 h.p. @5800 rpm and another time giving 24.7 hp. There are higher hp readings across the full range of 4000-5800 rpm, but no indication of why it was tested twice. My inference is that the first time it was too low, presumably at the highest rpm(?), and presumably with 24.7 having reached or exceeded the min. acceptable value(?). However, another "Racing" spec engine with "Special" valve springs tested on 14 October has 24.8 and 26.5 hp values at 5800 rpm. Since it apparently failed at 24.8, whereas four months earlier one passed at 24.7, this is consistent with them having moved the goalposts in the interim.

These are the only sheets I have that show two sets of data, but they seem to reveal something interesting about the bikes that we didn't know before. It's a shame all those dyno sheets are just collecting dust, essentially used only as decoration by owners, if they're used at all, when I could put them to very good use to extract interesting new information about Gold Stars.

Recently, MMan and I (re)visited the Barber Museum in Birmingham, AL, and in the succeeding days, I chatted on the phone with Brian Slark, who has retired from the Barber. Brian and I were not talking about this issue, outlined above, but one thing he talked to me about might shed some light on these bikes.

Brian was a famous scrambles and ISDT rider in his day, riding everything from Greeves (ISDT) to Goldstar (scrambles). Describing scrambles in the US, he said there was an imaginary line dividing the continent from north to south. To the east of that line, the off-road scene was very European. So the scrambles races were like British scrambles tracks, slow, 'nadgery' (a lovely Brit word for twisty) with lots of ups and downs. Western off road events were wide open, like the famous Las Vegas races, where 300 riders would line up in a huge line, and race away at full throttle to a mark several miles away. The so-called Desert Races. Races like the Catalina GP were similar; the course was ten laps of a six-mile course for the 500s.

So it makes sense that Alzina would have asked for, and been sent, scramblers with a lot of top-end power. Whereas a Gold Star being scrambled in the UK would have needed tons of bottom end torque, which the 65-2446 cam would have delivered.

Horses for courses, is the old phrase. And it seems particularly apt here.
Originally Posted by NYBSAGUY
...I will never rev these engines anywhere near their maximum power curve.
Originally Posted by NYBSAGUY
Horses for courses...
I don't know what cams are in my BB, but the dyno curves of this series show ~30-32 hp @ 5000 rpm (~24 with Touring cams), which is a fair bit below their redline of ~6500 rpm that I infer from the data. Interestingly, the Catalina and Competition are essentially the same at that rpm.

What this, along with the behavior of my Gold Stars, tells me is while they may have 40 hp @ 7000 rpm, what is actually useful is the 30 hp they have at 5000 rpm. That 30 hp provides very satisfying performance on the streets and highways from these 355-lb. bikes (the actual dry weight of my Competition). Of course, it would be different if I were preparing a Gold Star for AHRMA. But, horses for courses.

Addendum:
Originally Posted by NYBSAGUY
So it makes sense that Alzina would have asked for, and been sent, scramblers with a lot of top-end power. Whereas a Gold Star being scrambled in the UK would have needed tons of bottom end torque, which the 65-2446 cam would have delivered.
We know east and west coast Catalinas had some external differences, like magnetos vs. magdynos, but now I wonder if they might have had internal differences as well, like cams.

From memory a 1959 supplemental parts list for the Catalina has ~18 items on it but they're all external to the engine (such as the frame and air cleaner), implying those are the only changes from the British catalog. However, there's no letterhead on that list so maybe(?) it's for the east coast, and maybe(?) the west coast equivalent -- if there is one – shows Clubmans cams. Does anyone have relevant information on this question?
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