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#544613 - 05/22/14 9:15 am Megaphone discussion  
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Hillbilly bike Online content
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Running from demons in WNY
If you read my latest dyno pulls you'll see the engine makes good torque and HP from 3800-7250 rpm. Kinda like a stock 650 with 10 more HP and slightly higher RPM. The wide power band should make the bike easy to ride.. The exhaust is a simple 1-1/2 x 36 inch TT type pipes. My engine also does not like long intakes or stacks,a different story but likely linked to the exhaust.
The dyno shop does only bikes and snowmobiles and has seen 750 Brit twin flat track bikes on his dyno. He says best power and power band came from a two into one with a straight collector or short megaphone. He says individual megaphone engines have been peaky while making no more power than the collector system on a 360 degree twin. I can not disagree with a guy who has seen many exhaust system on many bikes on his dyno.
I see highly modified road race Triumphs like Tim Joyce's past bike using short primary pipes merged into a short collector. These may turn higher RPM's and I have no idea if they have 360 degree cranks so the comparison may not be valid.
I did fabricate a rather crude short primary two into one pipe that showed promise..But do to time limitations the TT pipes was the choice at the time.
OK, so has anyone tried a collector type exhaust on a 360 degree twin?
I have nothing against megaphones but if they give one HP at the expense of a peaky engine,I don't know about that.
Thanks.


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#544618 - 05/22/14 9:28 am Re: Megaphone discussion [Re: Hillbilly bike]  
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OK, so has anyone tried a collector type exhaust on a 360 degree twin?

Sorry no. All my tests were single pipes with individual megaphones.

ending up here. 1956 Norton 500 Dominator 360 twin. Petrol 97 octane




with pipes that looked like this


Last edited by johnm; 05/22/14 10:18 am.
#544623 - 05/22/14 10:15 am Re: Megaphone discussion [Re: Hillbilly bike]  
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Mark Parker Offline
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I would recommend a two into two through an 'X' connector. I do not think crank configuration makes a big difference to the pipes working, though it effects other things. Header dia can determine where the power is.


mark
#544628 - 05/22/14 10:21 am Re: Megaphone discussion [Re: Hillbilly bike]  
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Ron - in California R.I.P. Offline
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I do see more and more guys go with a two into one set up.. that should make tuning easier and get a nice wide rpm range. Power wise, dunno.. As an aside, try to separate the difference between a road race set up from a land speed set up..

Last night we watched one of the many Ack Attack videos.. they went through a lot to get where they got to... and in the end, when they got the record, the bike had a shifting issue and would not go past 4th gear, so they re-geared it for record speed in 4th. Then they raised the rev limiter a bit and added boost to make up for the wide gear spacing, it worked. The point is that often there is more than one way to make speed, even if the one option is less desirable, in the "heat" of the battle you have to do, what you have to do... This is a good video to show team work and keeping cool heads when the deadline approaches. This year I hear there will be a few teams trying to break their record.. could be a very fun year at Bonneville.

FYI, so far my bike does not like a long velocity stack. It lost top end power and gained mid range power.. changing the overall length did not improve that. I have a shorter stack on the way. Almost all the bikes I see have very short intakes / stacks. Perhaps they know something or just follow each other.. testing is how I will know. My old carb set up is very good.. the new carb is not as good.. yet.

Ron

#544654 - 05/22/14 11:29 am Re: Megaphone discussion [Re: Ron - in California R.I.P.]  
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Running from demons in WNY
We can't compare dyno power but we can compare the power curves.
This is the graph from a few days ago seen in my "Dyno" post.
9 inch total intake length from carb throat to intake valve, no velocity stacks,the mentioned TT pipes. This is a very wide power range up to 7250 rpm with no dips and 90 percent of maximum torque available from 4800-6800 rpm. the lesser power lines on the graph were with velocity stacks or a 1/4 inch bolt "restriction" in the exhaust pipe exit and jetting trials.
The dyno operator felt a two into one collector can get the power up a bit higher at 7000 plus RPM..



And this is the exhaust on Tim's very successful racer.Different breed of Triumph than mine...but...



650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#544679 - 05/22/14 2:10 pm Re: Megaphone discussion [Re: Hillbilly bike]  
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Ron - in California R.I.P. Offline
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Sorry to go back to it.. but your charts do not reflect any fuel mixture readings.. If you are not equalizing the mixture for each set up, you may be pe**** in the wind. On some bikes, one main jet size is worth most of one H.P. And I have found changes to either the intake or exhaust often changes the mixture several main jet sizes.. your comparisons may not be any good if those changes are not accounted for. For instance I made one intake change and the main jet went from a 225 to a 205. At first we thought we lost power.. after re-jetting there was a few tenths more. The basic rule is to make one change at a time, and maximize each change to get a proper comparison.

Ron

#544696 - 05/22/14 3:30 pm Re: Megaphone discussion [Re: Ron - in California R.I.P.]  
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Running from demons in WNY
I have other charts with A/F ratios, 12.9 was best.The best power curve was checked with by A/F and then jet substitution. 220 main was best,substituting a 210 or 230 was almost 2 hp loss at 1700 air density.


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#545134 - 05/25/14 9:05 am Re: Megaphone discussion [Re: Hillbilly bike]  
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Pre Unit Offline
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Both Actually !

SMITH had 1 3/4 headers, on a Saint 650 ( TR6P ) . Bonney Cams .
Tubes TTish to 2 1/4 Tube under starting at front of frame ,
as in the headers just went down then curved into tube at
twice the X- section . This went to a 14 in odd long Mega ,
about 5 in + at rear dia , or 6 in.Started about at rear of
trans , so lower tube was about 14 or 18 inches long .

Was effective for dealing with RDs etc , good of the line .
Reved to about 7000 with the single carb head , effectively .

boomed and grated / gnarled , rather than wailed . But only
loud within a kilometer or so , w.f.o. in still air .

#545152 - 05/25/14 11:51 am Re: Megaphone discussion [Re: Hillbilly bike]  
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quinten Online content
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Quote:
He says best power and power band came from a two into one with a straight collector or short megaphone. He says individual megaphone engines have been peaky while making no more power than the collector system on a 360 degree twin. I can not disagree with a guy who has seen many exhaust system on many bikes on his dyno.

As engine builders , this may be old hat to you , but i found this an Interesting article .

http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm

...."The computation of what actually goes on during an exhaust cycle is a highly complex problem in compressible fluid flow, the details of which are explained in detail in several texts, my favorite being Professor Gordon Blair's Design and Simulation of Four Stroke Engines. For the purposes of this article, the following overly-simplified explanation will serve to illustrate the principles.
There are two separate components to the exhaust event. The first is ..."

#545296 - 05/26/14 11:34 am Re: Megaphone discussion [Re: quinten]  
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I ordered basic megaphones and reverse cones from Megs/Cone Engineering.less than 50 bucks to weld up myself.
Be back on the dyno ,make adjustments and see what happens.
I'm thinking the engine is fully developed and there's no more power to be found without digging into the engine....But ya never know unless you try...
And there's always oxygenated racing gas that can be good for 3-5 percent power...But that fuel is said to be a slippery slope between best power and detonation..


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#546824 - 06/04/14 8:32 am Re: Megaphone discussion [Re: Hillbilly bike]  
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terra Australis
" And there's always oxygenated racing gas that can be good for 3-5 percent power "

what the film didnt make clear was Old Berts ' one for me & one for you ( the bike )'
with the Amyl Nitrate heart pills .

Used as model aircraft diesel fuel ignition improver . Only legal in N.Z. as antidote
for cyanide , with the possum hunters . DII is 50% amylnitrate and seems as effective .
dunno about for dicos though .

#546827 - 06/04/14 8:43 am Re: Megaphone discussion [Re: Pre Unit]  
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Gasoline racing classes require gasoline. Oxygenated gasoline is ok but doped up gas puts you in fuel class. Model airplane engine fuel for glow plug engines is very similar to nitromethane.


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#546834 - 06/04/14 9:27 am Re: Megaphone discussion [Re: Hillbilly bike]  
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Ron - in California R.I.P. Offline
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California
If you do a little research you will see some (many/most..?) gas stations have Oxygenated fuel. The Oxygen leans out the mixture on carburetted engines, which they "thnk" reduces emissions. If a lot of Oxygen is added, and the fuel mixture is not changed, then bad stuff can happen to your piston(s).

Ron

#546907 - 06/04/14 5:39 pm Re: Megaphone discussion [Re: Ron - in California R.I.P.]  
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VP sells oxygenated leaded and unleaded racing fuel...Yes you have the enrichen the mixture a few jet sizes .Guys say it's a fine line between more power and lean engine damage.


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#547999 - 06/11/14 8:24 am Re: Megaphone discussion [Re: Hillbilly bike]  
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I now have megaphones.I fabricated these from pieces bought from Cone Engineering. The reverse cones are removable for tuning....A lot of info on megaphones and for the most part the tuner needs to experiment on his particular engine to see what works.
I also shortened the intakes 1-1/2 inches.
The bike goes back on the dyno shortly to make comparisons ...






650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#548015 - 06/11/14 10:41 am Re: Megaphone discussion [Re: Hillbilly bike]  
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Ron - in California R.I.P. Offline
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Nice looking pipes.. now those look long to me (with the megas on)..! One key element people sometimes miss are the bents in their pipes.. your bends are nice - large radius. If you see bikes with very tight / sharp bends at the head, then someone does not understand how pipes work.

But I should tell you that lengths on both intake and exhaust need fine tuning.. more so on the intake side. I made a length change of 1/4" and that got me two H.P. My dyno guy says some top tuners go in 1/4" adjustments on the intake. On the exhaust side, 2 inch changes are too much, once you get close to what is ideal for your set up. Half inch on exhaust seems about right.

So, I had my exhaust pipe coated.. I only discussed the outer coating to make it look nice.. they coated the inside as well. I made no other changes to the engine that could affect power.. yet we got more power after the coating. My dyno guy said yes, that even a coating will change the effective length / speed of the exhaust. And in my case, I lost a small amount of power in the lower RPM range of 4,000 and gained power above 6,000. A great trade off, if I must say..!

OK, here is one "rule" that is difficult to follow, but... Make only ONE change at a time, test then make the next change. You changed the intake and the exhaust at one time. One of those changes may be great, the other may be the opposite, thus you have no idea, what did what.. Sorry, it is a hard rule for me to follow, so I understand, but this is how it should be done if you want the best results.

There is so much for me to still learn.. today is shipping day..!!

Good Luck..!

Ron

Last edited by Ron - in California; 06/11/14 10:43 am.
#548023 - 06/11/14 11:52 am Re: Megaphone discussion [Re: Ron - in California R.I.P.]  
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Ron,good luck to you with the racing


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#548034 - 06/11/14 1:15 pm Re: Megaphone discussion [Re: Hillbilly bike]  
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Alex Offline
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Let us know what you get with the megas. You mention Tim Joyce's bike: Tim told me he went around and around with megas and finally gave up due to gaps in the power band. I suppose it's different for road racing but he ended up with the collector with perf pipe inside. I came to the same conclusion but with a two-into-two exhaust on my A65. Useable power is sometimes more important than maximum power.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
#548035 - 06/11/14 1:28 pm Re: Megaphone discussion [Re: Alex]  
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Running from demons in WNY
My bike engine has a very nice power band with 1-1/2 x 36 inch TT pipes peaking at 7200 rpm.
From what I understand about megs is they cam make a peaky power band. And the reverse cones are supposed to make a better power curve but lose a slight bit on top end...Probably wind the same as the TT pipes....
Supposedly....two into one collector type headers are not that effective on 360 degree twins...
I don't want a peaky power band but all the top running LSR Brit bikes have long pipes with megaphones...
As they say in car racing,see what equipment the fastest guys are using...Then use the same stuff or spend a lot more time and money to go off in a different direction that may or may not work out better...


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#548067 - 06/11/14 6:02 pm Re: Megaphone discussion [Re: Hillbilly bike]  
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I used Cone parts also to make these pipes. I did not want 1-3/4 pipes.

Model airplane two stroke motors use methanol and castor oil with nitromethane add in the hotter mixes.

#548142 - 06/12/14 8:01 am Re: Megaphone discussion [Re: Hillbilly bike]  
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phantom309 Offline
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That system in the picture worked great on everything I put it on. I just made one for my BMW side car the same set up and it also seems to work well but will report back after the weekend :-) I now use a super trapp end so I can tune it better. That system in the pic rusted out so now stainless is the way I go .The rust also was getting pulled back into the cylinder on the return waves and causing cylinder scratches.. just something else to think about. You can do all the computer systems you want but rare they work, Keep the pipes about 29 inches and on 500's they like very small pipe like 1 1/4 inside and 750 seemed to like 1 5/8 inside. my 750 now has 2 into 2 now, high pipes because of room under the bike. not bad power too at 78 hp at the wheel.:-)It has a few trick goodies in it .


Tim Joyce
sponsors
D@D cycles
Works shocks
Glass from the past
#548143 - 06/12/14 8:05 am Re: Megaphone discussion [Re: Hillbilly bike]  
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Mark Parker Offline
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It would not be difficult to make an 'X' pipe to join the pipes just before the megaphones. It could be slipped on or replaced with straight tube to change back, it would be interesting to see the difference on the dyno. This one looks rough from the outside but the internal connection is really nice because of the curves of the pipes. The section is short enough to get an oxy torch at the inside to neaten up. I tried just a balance pipe between pipes but this seems much better. A 2into1 helps extract but then there is just the volume of one exhaust, this gives the volume of two pipes plus the extraction benefit, and might be something worth experimenting with.




Last edited by Mark Parker; 06/12/14 8:08 am.

mark
#548145 - 06/12/14 8:40 am Re: Megaphone discussion [Re: Mark Parker]  
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Running from demons in WNY
I'm familiar with X pipes from car experience.

What Phantom 309 (Tim) describes on his bike was the system I made in a hurry for the first dyno testing. 29 inch 1-1/2 primaries and a 3 inch diameter 17 inch long non tapered common collector. This made two HP less on the dyno than the later dyno test with the 1-1/2 inch TT pipes.In all fairness the bike had a battery failure, no spare battery so the testing was cut short. I should have refined the two into one pipes but....Guys were telling me the primaries were too short,the collector too short so I fabricated the TT pipes.

Looking at the power curve graph above you can see my bike with the TT type pipes has a nice power curve with 90 percent of maximum torque available from 5000- 6800 rpm. It's more like a stock 650 Bonneville with 12 percent more HP that peaks 3000 rpm higher. In reality the engine is just a Bonnie with a bit more compression and cam and large carburetors. I might be looking for more power that simply isn't there considering the present state of tune....


650 Triumph modified production LSR record holder 133.1 MPH... Twin 650 engine Triumph LSR that goes sorta fast...
#548996 - 06/17/14 6:33 pm Re: Megaphone discussion [Re: Hillbilly bike]  
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So I don't know much of nuttin' from nobody, but I will tell you what I have been told, and done, and what has worked for me, in about 25 years of racing Triumph stuff.

First, if you measure a set of factory TT pipes, you will see they are 43 inches around the outside of the bends, from front to back, and 1 3/4 inches in diameter. Time-tested dimensions. Works great on dirt, and road racing. Keep those numbers in mind.

When I first built my T140 road racer more than 25 years ago, I called guys all over the country to get advice. At that time, I was told by Jack Wilson at Big D in Dallas to build a system based on TT pipes, with 2 separate 1 3/4 inch diameter, 29 inch long head pipes, with 13 inch long cones that went to 3 1/2 inches in diameter, then a 1 inch long reverse cone that was 2 1/2 inches diameter at the outlet. Virtually all the AHRMA road racers at the time used those dimensions. I used that system for many years, and the result was low to mid 60's hp, and just a knick under 130 mph at Daytona, with very good overrev to 7500-7600 rpm. It accelerated very well, and was quite good on straights and on starts where you could control the rpm with clutch slip, but that system was very prone to megaphonitis or reversion, and basically just stumbled below 5000, so it was hard to get off turns on a road race track.

If you do the arithmetic, by the way, you will notice that system is also exactly 43 inches long around the outside, just like the factory TT pipes. This obviously is not accidental.

More recently I built another very similar system, with the same dimensions, but shaped as 2 individual high pipes, one on either side, with a sharp U bend at the head to bring the pipe alongside the cylinder, and I also added a perforated 3 inch long, 2 1/2 inch diameter core projecting out of the end of the reverse megaphone, and a straight 3 1/2 inch diameter, 4 inch long pipe section at the back of the megaphone, extending over the reverse megaphone, both ending at a flat end plate shaped like a big flat washer--in other words, a simple straight through muffler on the end. Whatever it was, the tight bend, or the muffler section, the megaphonitis/ reversion problems I had before were solved, and this one runs like a tractor, making useable power from about 4000 rpm on to 7200 rpm or so, although it doesn't overrev like the other set. I'm no tuner, but I assume the reason it worked so well is a little bit of additional back pressure. Even with the loss of overrev, it gets around a race track faster because of the better spread of power.

By the way, just for reference purposes, the 43 inch TT pipes end at the back of the engine, just in front of the rear tire, and the 29 inch head pipes end just below the front of the engine, so you can always use those dimensions to guesstimate the length of the overall system or the head pipes of any bike you are looking at.

Tim Joyce's bike was much stronger than mine, and he is a much better rider than me, so whatever he says, do it. Anyway, on his old Sportsman bike he used similar length head pipes (or slightly longer, like 31 or maybe at most 32 around the outside) and then a 2 into 1 collector and a relatively short muffler after that, roughly the same overall length as the factory TT pipes (or perhaps just a little longer), and they look to be 1 3/4 diameter. I will probably get around to building a siamesed system like that at some point, because it seems that is the best road race style answer where you need to get off corners and need mid-range power. For top end, though, I am guessing the separate 1 3/4 29 inch pipes, 13 inch meg, 1 inch reverse cone might be best.

There are a lot of opinions on this stuff out there. I was told a bunch of times that 1 3/4 diameter pipes were best and smaller diameters didn't do anything (Neil Keen), or that they were ridiculously large and would not work, etc. etc., that the 43 inch pipes were too short, that 13 inch megas were too short, etc., etc. To-may-to, to-mah-to. What I do know is, whenever I experimented with longer pipes, the motor slowed down.

So there you go, I'm no tuner or scientist, but that is what I was told, and what I did. For what it is worth. Your results may vary.


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