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where do the coil wires go on dual plug heads? #577134 12/19/14 10:25 pm
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kevin roberts Online Confused OP
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i had my T120 cylinder head drilled for dual plugs many years ago, and have run a markIII Boyer on them with excellent results.

i just read this on the Boyer website:

Quote
The Micro Power Coils
. . . With most dual output coils it is good practice to have only one output feeding a compressed cylinder, but with 35,000 volts it is possible to have both outputs feeding a compressed cylinder at one time.


i've been running both plug wires from a single dual lead coil to the same cylinders: left coil, left spark plugs . . .right coil, right spark plugs. the bike has run extremely well this way, but i'm wondering if i fail to understand something.

what are the recommended destinations for the four plug wires leaving two dual plug coils in a two cylinder motor?





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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577169 12/20/14 9:37 am
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Kevin, with your dual plugs, are you running less advance with the timing? If so do you know about what its set at ?

Last edited by konon; 12/20/14 9:38 am.

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Re: where do the coil wires go on dual plug heads? [Re: NickL] #577255 12/20/14 7:52 pm
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Originally Posted by NickL
Each cylinder would have one lead from each dual coil attached. That way each coil fires one compression stroke at a time. This will improve your sparks that's for sure.

Nick


this is what i read, now. originally, i connected the system leftie/rightie because i thought that if one plug would fire easier than the other, then all the spark energy from the coil would be diverted to the easy plug, and the compression plug wouldn't fire at all.

is that not the case? i'm not a rocket scientist when it comes to ignition.



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Re: where do the coil wires go on dual plug heads? [Re: konon] #577262 12/20/14 8:34 pm
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Originally Posted by konon
Kevin, with your dual plugs, are you running less advance with the timing? If so do you know about what its set at ?


nope, i put them in because at the time the best gasoline was 89 octane unleaded premium. i'd been trying all sorts of things to keep it from knocking-- MTBE made the pistons orange, Pep Boys octane booster made the plugs (and me) black and sticky, extra base gaskets did weird things to the rocker arm ratio.

when i put the two-plug head on, i left the timing at 38 BTDC, right on the rotor marks, and it ran great, no spark knock. it did what i was looking for then, and i haven't changed it since.

but i'm making a lot of changes to the machine, and looking much more closely at fuel and spark settings is in the plan.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577265 12/20/14 9:09 pm
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and speaking of dual plug ignition ... It's not always known, but when fitting dual plugs in a single cylinder bike like our Goldies, you Must use two separate coils with the primaries connected in series vs fitting a dual output coil. Bear in mind a dual output coil isn't two coils in one case, but there's a spark plug lead connection to either end of the single HV windings. Because of this the voltage output to each plug is halved if they are both needed to fire at the same time under compression.
BTW, I've ended up tuning with the dual sparks by only retarding the ignition ~2 degrees, vs the 10 degree retard so often 'heard'. hmmm

FWIW .. With my road Goldie with dual plug ignitions I use the SRM/Boyer systems with two Boyer coils. Interestingly the total loss Boyer 'crank triggered' system on our dirt tracker uses a different Boyer box that is triggered with a modern design 'reluctor' sensing a steel tab on the primary belt pulley vs those delicate magnetic pickups in the typical Boyer set up.
For my latest GS project bike I have a yet untried Power Dyno alternator/ignition unit set up made in GER to fire dual plugs. We'll see.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577280 12/20/14 10:59 pm
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With a dual-lead coil, the current has to go through both plugs to complete the circuit. If one plug fouls, that can still happen. The current will just travel down the insulator around the centre electrode to ground, instead of having to jump the plug gap to reach ground.

If the coil has to fire two plugs, both on compression, you'll need a helluva voltage (about twice what it normally takes to fire a single plug). That might not be good for the coil. Coil voltage only rises up enough until it can jump the plug gaps (in that case, very high).

If one plug is on the exhaust stroke, it takes very little voltage to jump that gap, and most of the voltage is used to fire the other plug on compression.

Re: where do the coil wires go on dual plug heads? [Re: Dave - NV] #577295 12/21/14 1:33 am
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Originally Posted by dave - NV
triggered with a modern design 'reluctor' sensing a steel tab on the primary belt pulley vs those delicate magnetic pickups in the typical Boyer set up.

You mean just like the Lucas Rita? What an idea!


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577311 12/21/14 4:46 am
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Quote


i've been running both plug wires from a single dual lead coil to the same cylinders: left coil, left spark plugs . . .right coil, right spark plugs. the bike has run extremely well this way, but i'm wondering if i fail to understand something.




You're putting a bit of a strain on the coils. It might shorten their life.


Amateur Loctite enthusiast.
Re: where do the coil wires go on dual plug heads? [Re: DavidP] #577312 12/21/14 4:50 am
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Originally Posted by DavidP
Originally Posted by dave - NV
triggered with a modern design 'reluctor' sensing a steel tab on the primary belt pulley vs those delicate magnetic pickups in the typical Boyer set up.

You mean just like the Lucas Rita? What an idea!


My crank triggered Boyer Micro Power had a fairly delicate looking magnetic pickup.


Amateur Loctite enthusiast.
Re: where do the coil wires go on dual plug heads? [Re: triton thrasher] #577378 12/21/14 2:51 pm
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i'm thinking about all this.


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Re: where do the coil wires go on dual plug heads? [Re: konon] #577442 12/21/14 9:58 pm
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Originally Posted by konon
Kevin, with your dual plugs, are you running less advance with the timing? If so do you know about what its set at ?


The timing is set at a factory figure that is usually determined on the dyno. As Nick L mentions, any variation to the head will lead to the need to put the bike on the dyno and determine where the new timing number is.

The use of dual plugs is often for practical reasons like Kevin's avoidance of pinking. Some use it because the starting is more reliable. Dual plugs can allow the timing to move closer to TDC simply because there is a likelihood that it will speed up the combustion process. If your head is really inefficient, the combustion process will take quite a while. If it is efficient it will be quite quick. What you are shooting for is to have the highest mean effective pressure at 12 degrees ATDC.

If the pressure peaks at TDC, the piston and connecting rod will "stiff arm" the pressure and there will be a loss of power. If the pressure peaks BTDC, it will slow the momentum of the flywheel and thus reduce power. Both of these early power peaking possibilities will put additional strain on the components. If you go to the dyno, you can time the bike for peak power by moving the ignition a small amount for each run until the power drops. The power will drop if you go too far because the piston will already be on its way down when the highest pressure occurs. You can then go back to peak power and that is where your new timing will be.

If your timing is at 38 degrees it takes a total of 50 degrees to get to the "sweet spot", which is a long time. Some engines with deep combustion chambers take even longer. Additionally, if you are firing your intake charge at say 40 degrees rather than 20 degrees, you are starting the combustion process short of your maximum compression ratio, which occurs at TDC. This will lower power also. All this to say, the dyno is your friend!

David

Re: where do the coil wires go on dual plug heads? [Re: David Dunfey] #577457 12/21/14 11:24 pm
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okay. dave in NV pointed out that the secondary windings inside a dual lead coil are actually two ends of the same winding. this is an image of something like it i've found after some looking:

[Linked Image]

ignore the double switching device.

i can understand the idea that two spark gaps on a compression stroke have more trouble ionizing the gap than two plugs on an exhaust stroke, given that the total voltage available in the coil is fixed.

what i'm still not grasping is why both plugs on the same coil fire, if they're separated into one cylinder on compression and another on exhaust. if there is a big imbalance between the voltages necessary to spark them, then why doesn't all the spark energy get diverted to the cylinder on the exhaust stroke?

if that plug sparks at a lower voltage, why doesn't it simply leak down all the energy out of the joint windings, and allow the plug on the compression stroke to misfire all the time? don't misfiring gasoline-fouled plugs on a single tower coil do this by leaking all the electricity down the ceramic and out? why doesn't this happen when the wires are connected between cylinders?

Last edited by kevin; 12/21/14 11:30 pm.

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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577461 12/21/14 11:41 pm
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well, in addition to all your suggestions that i'm straining the coils (they're old harley 6V things, and seem to be able to take it), i'm glimmering that i might be straining the engine in general by NOT retarding the spark, if the cylinder pressure is peaking before TDC due to better flame travel. this is the culprit of my confusion:

[Linked Image]

i run a standard NGK B8ES in the 14mm holes, and then something else that i can't remember at the moment in the 12mm holes in the center. the idea behind this was to start the mixture burning at both ends. the pistons are the morgo 9.5:1 (i think), so the crowns aren't awfully high, but the combustion space is still the nasty old grapefruit rind-shape at TDC.

the 12mm plugs have a too-long reach, and they're held up on brass spacer pieces to keep the threads out of the combustion chanmber.

Last edited by kevin; 12/21/14 11:42 pm.

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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577504 12/22/14 9:40 am
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Kevin,who did the work for the dual plugs? hopefully the two added plugs in the center miss each other. grin
I'm thinking about doing a 650 dual plug conversion myself. But I'm unsure exactly where to drill the pilot hole...Might just have to practice on a junk head...
I had a talk recently with Franz and Grubb, a well know Triumph shop in California. I was told they don't believe a dual plug conversion is worth the trouble for an engine with stock 9-1 pistons. It's just a conversation piece that adds complication. An easier approach is to use MAP tight quench lower dome pistons that give the same compression as higher dome stock pistons if you are rebuilding the engine...
Their opinion,not mine...I would think if you only have low octane fuel available it's a good idea to dual plug.
Hate to mention Harleys,apples and oranges, but I will...I dual plugged a iron head Sportster and a big twin Shovelhead. Both engines had higher compression and hotter cams.
Making on the street comparisons between the normal plug only and dual plugs,the engine ran the same....But the dual plugs did help eliminate detonation.
And I originally wired the engine with one coil per cylinder...Not a good ideal...


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577522 12/22/14 12:07 pm
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Originally Posted by NickL
You have drawn single ended coils with the normal grounded end of the secondary, you have a single secondary which is connected to 2 plugs, one at each end. To jump a gap at atmospheric pressure takes little energy so the plug which is not under pressure will arc across and as an arc has no resistance will complete circuit to ground so the large energy will ionize the plug at the pressurized end.


nick, is this a better image of what you're saying is in there? i think in pictures.

[Linked Image]

i understand verbally the idea that the exhaust plug will fire with a weak spark, and the compression plug will fire with a hotter spark, but i don't see what pete was saying about the current having to go through both plugs to complete the circuit to ground. still seems to me that one plug could be ignored. obviously, this doesn't happen, because the engines run this way. i'm still trying to understand why the north half of the electrons don't all hurry backwards through the low-resistance windings and misfire.


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Re: where do the coil wires go on dual plug heads? [Re: Hillbilly bike] #577531 12/22/14 12:48 pm
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Originally Posted by Hillbilly bike
Kevin,who did the work for the dual plugs? hopefully the two added plugs in the center miss each other. grin


it was done by Big D in texas. the two 12mm plugs go in at a steeper angle than the stock plugs and just miss each other on top. in fact, the rubber spark plug boots are in firm contact. but because all the plugs fire at once, i've never understood that to be a problem.

as far as i know, franz and grubb might be right. as i understand it, the whole idea of moving the plug to the middle or adding one on the other side is to shorten the distance the flame front has to travel to get to the dead-end space down on the other side of the piston dome. if you've got really good turbulence from squish or from intake porting, then i guess you can accomplish the same thing, and a lower-dome piston would stay out of the way and let it happen.

but the domes raise the compression ratio, and if the extra plugs can make it burn okay with 10.5 to 1, then all other things being equal, you'll be faster than you would have been with 9 to 1.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577538 12/22/14 1:52 pm
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I'm interested in doing dual plugs,and can do in my drill press...But the cost of the tools probably exceeds the cost of a experienced shop doing it.
There used to be a guy here on Brit Bike that did dual plug conversions...Anyone know his name????


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: Hillbilly bike] #577567 12/22/14 4:02 pm
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if you drill them in the center of the head, the only thing to be careful about is making sure you stay clear of the valve seats. when i had Big D do mine, i stupidly didn't tell them that i had just had MAP install 3/32-inch oversize intake valves, and they nicked the valve with their bit:

[Linked Image]

they didn't say anything, and just installed a different valve with a different head shape and different spring pack. i didn't know until i next took the head off and discovered that their odd valve was tapping the edge of the valve pocket on the morgo piston. i took it off and had the pockets milled a bit deeper and wider, and solved that problem. it was my fault for not letting them know the head wasn't standard.

but their flycutting was exquisitely done. look at how they milled through the top fins on the head:
[Linked Image]

[Linked Image]

if i had told them about the oversize valves, the work would have been perfect. even so, the head has worked well for many years.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577570 12/22/14 4:24 pm
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Kevin .. I've not seen or heard of a 'dual output' coil as your drawing shows. Certainly a different concept than the typical dual output coil. Do you have more info on it?


Hillbilly ... Harold with Johnson Cams in WA has added the dual 12 mm plug hole for me on umm.. 5 Gold Star heads. He has the shop machine tools, the experience and the talent to do a nice job. As the 2nd 12mm plug in my GS heads are vertical into the backside of the chamber due to the limitations of the location due to the rocker box. In this case a long reach 'extended tip' 12mm plug fits down better into 'pocket' cut into the chamber.

But ... 'I've been told' that moving the plug hole location and changing to a little 10 mm plug to allow squeezing it closer to the valve seats is as good as a dual ignition set up in our olde inefficient hemi head combustion chambers. This is certainly not a 'new idea', but I've not tried it. John Healy, what's your opinion on this??

Most of us have heard of The Era's tuning wizard/rider Dick Mann. He had already changed to total loss battery ignition vs the power loss spinning a mag. Here's 'A story' telling of a illegal mod at that time to the ignition of his Gold Star pro dirt tracker. He had located a 2nd central 10mm plug directly between the valve seats. The plug fired into a small cavity and then through a slot between the seats into the chamber. After awhile he was found out and had to disconnect the secondary ignition.
What's interesting about this idea is many years later the Honda auto factory 'invented' somewhat the same concept to ward off detonation sparking their 'lean burn' high mileage engines into a cavity connected to the combustion chamber.


Dave - NV
Re: where do the coil wires go on dual plug heads? [Re: Dave - NV] #577587 12/22/14 5:25 pm
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Ya mean the CVCC engines?

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577599 12/22/14 6:10 pm
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Setting up "squish" so it actually works is more than putting in a set of new pistons. This is especially true when you have a head that has had the head gasket surfaced skimmed. There is a narrow window where having a squish area actually works. The target recommended by a lot of "tuners" for a Triumph is .032". If you are racing on a short track you can go as little as .025" and the pistons will not hit the head, but at Daytona you need the full .032" or there will be contact. The squish is easy to measure by laying 4 or 5 "u' looped pieces of solid solder around the outside edge of the piston and rotate the engine over with the head on just once. You can then remove the solder and "mike" the area that was squished.

For our 500's we always got semi-finished pistons from Aries. The valve pockets were cut, but the rest of the top and underneath the dome were not. This allowed us to accurately cut the squish area on the head and match the piston to it. To get a squish band on a 500 you have to use the early squish head.

Part of setting up the crush, and getting everything square, included shaving material from the base of the cylinder. Then we could use various thickness copper base gaskets to vary the squish.

[Linked Image]

The head would look like this: The valves are skimmed to allow them to clear each other on overlap. As it is, there is just .060" between the valve margins as they cross each other at TDC. The early 500 head has a shallower valve angle than the later head and is a lot more work to get right than the later head.
[Linked Image]

When searching for the right timing for the dual plug I got to use Daytona where I found 25° on both the 750 twin and 500 gave the best lap times.

All this is interesting to some of us nuts, but it has little to do with reality... IMHIxperience if you are having problems with pinging I would look into it. Twin plugging helps a lot. If the bike runs well as it is, leave it alone.


Last edited by John Healy; 12/22/14 6:34 pm.

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577620 12/22/14 7:47 pm
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As others have said, that wire on your schematic the leads from the centre of the secondary winding back to the primary shouldn't be there. It doesn't exist on every dual lead coil I've checked.

The secondary winding is completely insulated from the primary and on its own. One coil lead is positive and the other is negative. The current flows through both plugs and across the head between the plugs to complete the circuit.
If one plug is fouled, or even if you joined its plug lead directly to the head, the other plug will still fire (if that's not fouled, too).

Re: where do the coil wires go on dual plug heads? [Re: Pete R - R.I.P.] #577625 12/22/14 8:17 pm
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catching up . . .

Originally Posted by NickL
You are still drawing a ground connection on the secondary of the coils.....there isn't one.
. . .
I thought most blokes used 10mm plugs for the second set these days.


i've never taken a dual-plug coil apart, so i was guessing at the windings. so the voltage in the secondary in the coil is completely induced by the adjacent primary windings.

Originally Posted by Pete R
. . . One coil lead is positive and the other is negative. The current flows through both plugs and across the head between the plugs to complete the circuit.
If one plug is fouled, or even if you joined its plug lead directly to the head, the other plug will still fire (if that's not fouled, too).


^^^ okay. now i think i understand. i didn't realize the polarities were different. this means one plug sparks from the side electrode to the center, and the other from the center electrode to the side, correct? so neither can complete the circuit to ground unless current flows through the other.

my center plugs are NGK D8EA, 12mm. i have a picture of them showing the spacer, but transferring photos from a telephone to the net is defeating me at the moment.


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Re: where do the coil wires go on dual plug heads? [Re: NickL] #577630 12/22/14 8:53 pm
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Originally Posted by NickL
We won't go into the realms of preferred electron emissive flow with heated anodes etc.
Suffice it to say that dual ended coils work very well.


agh

yes, please, spare me. i already confessed i'm no rocket scientist on ignitions. i have enough trouble figuring out the easy stuff.

Originally Posted by NickL

The advantage of the 10mm plugs is that they don't seem to induce the cracking between valve seats that larger ones do.


i've heard about that when the plug hole is drilled right at the top. there isn't much metal to spare there.

back when i had this done MAP said they were experimenting with duals using 14mm plugs. i don't know whether they were ever successful at it.


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Re: where do the coil wires go on dual plug heads? [Re: John Healy] #577631 12/22/14 8:58 pm
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Originally Posted by John Healy

When searching for the right timing for the dual plug I got to use Daytona where I found 25° on both the 750 twin and 500 gave the best lap times.


that is not a lot of advance compared to the stock figure, john. i didn't realize how significant the improvement in burning was.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577717 12/23/14 10:51 am
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Re: where do the coil wires go on dual plug heads? [Re: Transgarp] #577737 12/23/14 1:03 pm
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i'm fascinated.

trans, why the switch from the 14mm to the 10mm plug in the old hole?

who did the porting?


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577876 12/24/14 9:54 am
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Originally Posted by kevin
i'm fascinated.

trans, why the switch from the 14mm to the 10mm plug in the old hole?


To install the same type of spark plug as on the two new holes, to decrease the hot points around the spark plug and especially to avoid too much weakening the medium of the head by drill two large hole of 14 mm

Originally Posted by kevin
i'm fascinated.
who did the porting?
Me wink

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577895 12/24/14 12:12 pm
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trans, the NGK D8EA plugs i'm using need a brass spacer in order to stay out of the chamber:

[Linked Image]

[Linked Image]

i'm really interested in the pazon ignition you're using, as i have a new project in the works. they provided much more information about the modification than i had available when i did mine some 30 years ago. this was all i had to work with at the time:

[Linked Image]


trans, how do you like the pazon system? have you found any faults with it?


every day you do not take a chance is a day of your life that you will never get back.
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #577953 12/24/14 8:12 pm
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yes.

very impressive. i've obviously got some testing to do. even setting the timing omn my machine at the (way advanced) 38 BTDC still didn't put peak pressures on the uphill side of TDC, though, because the motor wouldn't detonate after the change.

the pazon literature for the system that transgap uses recommends 32 degrees BTDC for total advance at 4000 rpm or so. clearly there's some room for fiddling with all this.

wonder how much horsepower i've been leaving on the table all this time.


every day you do not take a chance is a day of your life that you will never get back.
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578216 12/27/14 9:12 am
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Pinking over 28° with Morgo 750 cc 9.5:1 cr & Quebec cheap 91 octane fuel

I prefer the spark plug NGK CR8EIX Iridium which resists the fooled better that spark-plug NGK CR8EA standard

I use 8 oz Torco by tank for eliminate residual pinking

Spark plug color of my Triumph

[Linked Image]

Last edited by Transgarp; 12/27/14 9:16 am.
Re: where do the coil wires go on dual plug heads? [Re: Transgarp] #578223 12/27/14 10:29 am
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interesting that you still have pinking over 28 BTDC. that is in line with what people have told me to expect from a dual plug conversion in this thread.

your plugs show the pretty orange of the MTBE in the Torco octane booster.

i have had no fouling problems at all since i abandoned Champion plugs for NGK.


every day you do not take a chance is a day of your life that you will never get back.
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578347 12/28/14 10:38 am
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My Triumph started to undergo the problem of knocking since the arrival of the unleaded gas in Quebec at the beginning of the years 1980
Formerly I ride to 38° full-advance without any problem with the gasoline with lead

I say well that it is knocking, because pinking does not disappears when one put ignition retard; the knocking yes

I speak about it at greater length on my Web server

English version
http://transgarp.dyndns.org/Motorcycle/Knock-Pink-en.html

French version
http://transgarp.dyndns.org/Motorcycle/Knock-Pink-fr.html

Re: where do the coil wires go on dual plug heads? [Re: Transgarp] #578367 12/28/14 12:02 pm
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on my T120, hard detonation was clearly audible-- sharp metallic knocks, identical to hammer blows on metal.

i have no experience with any sounds from pre-ignition, and no evidence that it occurs.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578385 12/28/14 1:32 pm
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Quote
Spark plug color of my Triumph


These observations are from looking at your picture. It is not the same as actually looking at the plug.

Look at the threads. They looked heated at least half way up, where I would expect to see only two or three threads colored from heat.

What puzzles me is this is a fairly cold plug with most of the heat going directly into the body of the plug above the point where your plug' threads display heating. Just how hot does this engine run? I suspect retarded to 28° it must be running pretty hot. Of course these observations are subject to what I can see in your picture.

Also the orange deposit masks the plug not allowing one to check it for temperature of fuel mixture.

A side note: Here in New England we get very few real warm days, but I have had the chance of riding a long stroke 750 (aka Morgo etc.) belonging to Bill Getty in Southern California in the Summer (100°F) two up - me at 230 and the bride at 150ish from sea level in Santa Barbara through San Marcos Pass and up and around Figueroa Mountain on several occasions. It was a TR6, 5 speed, running on Californian pump gasoline, one of Bill's Keihen carburetors that was on test and it had a 750 long rod cylinder with 9:1 pistons. It neither missed a beat or pinged unless I really, really lugged it which I did on a couple of single track switch backs that seemed to gain 30 feet in elevation in 60 feet of asphalt. ANd having the carb on test Bill suggested that I abuse it a bit to see what I thought of the new carburetor.

Last edited by John Healy; 12/28/14 1:48 pm. Reason: side note

Re: where do the coil wires go on dual plug heads? [Re: John Healy] #578390 12/28/14 2:21 pm
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Originally Posted by John Healy
I suspect retarded to 28° it must be running pretty hot. Of course these observations are subject to what I can see in your picture.


Impossible to ride my bike to more 30° without increasing the detonation severly and decreasing the engine output with low rpm
Before 1982 I ride to 38° full-advance without problem and my spark-plug were held brown clearly with the super lead gasoline
Since 1982 I did not have the choice to move back with 28° not to scraping the engine by the detonation

About the air/essence mixture I use 2 AMAL 930 with #190 main jet
In 1974 I used #220 main jet, but too rich with the unleaded gas

The unleaded gasoline of Quebec is too low in octane number compared with the USA wink

Re: where do the coil wires go on dual plug heads? [Re: NickL] #578496 12/29/14 12:41 am
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Originally Posted by John Healy
Just how hot does this engine run? I suspect retarded to 28° it must be running pretty hot. Of course these observations are subject to what I can see in your picture.


john, i recognize that race conditions aren't road conditions, but you mentioned earlier that you ran this sort of head successfully at 25 BTDC. that's even more retarded than transgarp (nothing personal), and in a normal engine ought to make it run hotter. but as i understand it, if the engine runs best at a certain timing, then that's where most of the heat is being used to move the piston, and the engine shouldn't run hotter at that setting even if the figure is nominally way retarded.

i'm assuming that advancing to just short of detonation will make peak horsepower.

is that what you mean? why would you expect 28 BTDC to run hotter, if that's where the most energy is being used up in piston movement and isn't just being absorbed by the motor?

Last edited by kevin; 12/29/14 11:57 am.

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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578557 12/29/14 1:14 pm
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Quote
john, i recognize that race conditions aren't road conditions, but you mentioned earlier that you ran this sort of head successfully at 25 BTDC. that's even more retarded than transgarp (nothing personal),


From reading his posts he has given no indication that he has the head twin plugged.

Even reading his latest post:
Quote
Impossible to ride my bike to more 30° without increasing the detonation severly and decreasing the engine output with low rpm Before 1982 I ride to 38° full-advance without problem and my spark-plug (ed. bold) were held brown clearly with the super lead gasoline Since 1982 I did not have the choice to move back with 28° not to scraping the engine by the detonation


Even reading this I get the idea that the engine is single plugged. Triumph did extensive tests on the T140 using low octane unleaded fuel at MIRA as this is the fuel they had to certify for DOT emissions testing. They found that the engine was least prone to detonation (single plug) at a very narrow timing window of 37°.

The Triumph combustion chamber, especially on the larger bore of the 750, has a rather slow flame propagation. Putting in two plugs effectively cuts the time it takes for the flame front to travel in half. Thus the need to change the timing to something in the 25 to 30 degree range.

Califonia gasoline is nothing to write home about, but from Petro Canada's web site it doesn't seem that Canadian gasoline is out of line with the US:
Quote
The octane number written on the gas pump is Anti-Knock Index (AKI). It’s an average of two octane ratings using the same test equipment but using different operating conditions. The methods produce a Research Octane number (RON) and a Motor Octane Number (MON). Both were once considered important and that’s why AKI is an average of the two. With modern engines and fuels systems, recent studies have shown that RON is more important than MON. So in these cars, the higher the RON the better these cars perform. For an AKI rating of 91 the lower the MON the higher the RON. This difference is called sensitivity. All gasoline components have different sensitivity. Most hydrocarbon components have low sensitivity. Ethanol has high sensitivity and so, modern performance cars benefit from gasolines with ethanol. Why does ethanol have higher sensitivity? One reason is related to the cooler combustion that results from ethanol combustion. Higher knock tendency is directly related to higher combustion temperature.
Here is a comparison of two fuels with different octane with and without ethanol.

91 Grade - no ethanol
RON 97.2
MON 85.6
Ultra 94 - with ethanol
RON 101.5
MON 88



Even their AKI research RON number, the one referred to in Triumph owner's manuals, is 97 RON.


Re: where do the coil wires go on dual plug heads? [Re: John Healy] #578592 12/29/14 4:36 pm
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Look at John.
Yes one or two spark-plug little to make a difference, but I installed one 2nd spark-plug towards 2002 which is more than 20 years after having known my first troubles of detonation with the unleaded gas.
I have ride of 1982 to 2002 approximately with only one spark-plug by cylinder, the super gasoline unleaded, 20° full-advance and the detonation
Since 2002 that I ride twin plug by cylinder by Pazon and 28° with the threshold of the detonation
Since 2014 I eliminated any detonation with Torco and I could surely adjust with 32° or more, but I prefer to leave with 28° if ever I would miss it of Torco.

Come to live in Quebec with the gasoline [***] which is sold and you will include/understand wink

I have friends who noticed a large difference when they go to the USA
They have the impression to have more power with the engine of their vintage British motorcycle
There is surely a difference in manufacture of the gasoline sold in Quebec and the USA
Because formerly there was of it no problem


About ethanol, I am really not interested in ride with
It is manufactured based on water and many parts of the engine are sensitive there, especially AMAL carb & fuel tank

Last edited by Transgarp; 12/29/14 4:43 pm.
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578608 12/29/14 6:19 pm
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well, i obviously have some testing to do. it seems clear to me that i'm missing something with the ignition timing in my machine. if the optimum timing for a typical two-plug head is in the vicinity of 25-28 BTDC, then i shouldn't be able to run 38 without peak cylinder pressures occurring way early. if i were running god's own octane gasoline, then maybe it still wouldn't detonate, but horsepower should be down compared to the retarded figure.

i'm wondering whether having the two plug leads connected to the same cylinder negated the effectiveness of the two-plug conversion. doesn't seem so, because i haven't had detonation issues since then, although i continue to run the highest octane fuels i can find.

i've been using the 110 octane leaded racing fuel available from one of the gas stations near where i live. i'm guessing that has had an effect.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578617 12/29/14 7:06 pm
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Quote
Since 2002 that I ride twin plug by cylinder by Pazon and 28° with the threshold of the detonation


Do you have the Smart-Fire Triumph/Bsa/Norton Unit Twin 180° Crank TWINPLUG 12 Volt system or the standard Smart-Fire - Sure-Fire etc, running as a twin plug system. It makes a difference because the advance curve is different and not appropriate.

As I said above 25° to 30° full advance timing using a specific twin plug system designed for a twin plugged engine would be appropriate.

Quote
I have ride of 1982 to 2002 approximately with only one spark-plug by cylinder, the super gasoline unleaded, 20° full-advance and the detonation


I am not surprised you had detonation as 20° full advance timing (the retarded timing would be near TDC) with a single plug Triumph head would certainly be problematic. The timing itself would have caused your detonation no matter what the octane was. You were lucky you didn't hole a piston from pre-ignition.

And a bit of nit picking but the 91 Grade number on the pump is NOT an octane measurement. It is what is called the Anti-Knock-Index. As shown in the Petro chart above 91 grade (AKI) has a research octane number of 97 and a motor octane number of 85.

Coming to the US and having having more power because the fuel has more octane confuses me. Higher octane fuel does not contain any more energy than lower octane fuel. The only thing a higher octane rating does is to slow down the rate of combustion. Yes, the engine will not detonate because high compression pistons or high cylinder pressures caused by lugging or heavy load. What is called drive ability (no pinging, etc.) will be better, but it will not have any more power.


Re: where do the coil wires go on dual plug heads? [Re: John Healy] #578627 12/29/14 8:28 pm
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Kevin,

I did not realize that you were using such high octane. As John intimates, it may be the reason the combustion process is so slow. It is my understanding that you will produce the highest power using the lowest octane fuel that works with your compression ratio. Going lower or higher in octane will reduce the power. Unfortunately, the compression ratio is like the "pump number", it often does not relate to what you want to know. The advertised compression ratio of the piston, say 9:1, is a theoretical number based on 180 degrees of compression. Your "effective" or "dynamic" compression ratio is based on where the intake valve closes, which is dependent upon you cam and valve timing. Often, this means that your dynamic compression ratio is really 8:1. On top of this, you have the issue mentioned earlier that the advertised CR assumes that the spark theoretically occurs at TDC and as we know, it is happening much earlier.

I am not sure what you are shooting for, but if you are looking for power, you need to optimize all these compromises that you are required to make. If you know what octane is readily supplied as premium, you could adjust your CR to make the most power on premium and this would most likely mean adjusting your timing to suit. Unfortunately, to do this, you have to record numerous measurements on your engine.

David

Re: where do the coil wires go on dual plug heads? [Re: David Dunfey] #578634 12/29/14 9:17 pm
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Saying that higher octane gas burns slower is not always true. And how higher octane lessens detonation is a lot more that overall slower combustion.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578635 12/29/14 9:19 pm
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John, you seems to me skeptic and to think that I did not test all the possible solutions.
A given moment I bought a Honda XL600R 1986 new to rest problems of Triumph with the unleaded and to ride without gasoline concern to have fun in the sand pit
Before buying the Honda, I had good results on Triumph with 38° with one mix 50/50 of super gasoline unleaded 91 and the gas of octane 110 plane
I have this Pazon since 2006

Since the installation of the head twin-plug in 2002, I had the same problems of detonation with the Boyer Micro Digital connect on two twin coil 6V in series
When you speaks to give the full-advance to 38°, this implies that you do not believe in my problem of knocking and thinks you seems to think pinging which is not the case
I have failed to tear off me the leg by starting the bike with the kick when I gave the full-advance of origin to 38° towards 2008 and the engine was very unstable with the idle and wanted to spit the pistons because of the detonation if I gave too throttle to low mode
Normally with pistons Morgo 9.5:1 I must ride with AKI of 94 at least to ride 38° full-advance and only Petro-Can with ethanol allows it
But I am against the fact of ride with water in the engine of Triumph some is the percentage kind 5%
The majority of people of Quebec lowers compression with 8.5:1 to ride to 38° without problem, but with a loss of power that I to allow me little.
Then I do not have the choice to juggle with threshold of the detonation to keep a maximum of performance without being obliged to ride with of VP-Racing.

My Web site reads again well on the difference between pinking and knocking for better seizing on the content of my problem.
Because for the moment Torco is the most rational solution if I want to roll on the forest roads to the North of Quebec or only the ordinary gasoline unleaded is available

Gasoline of the USA really unleaded?

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578637 12/29/14 9:32 pm
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David

I have camshaft of origin with normal overlap for Triumph

I already used a set of camshaft of competition to strong overlap and dynamic compression decreases much in proportion of overlap and I did not have a problem of detonation when I tested them with unleaded super
But I do not like this kind of camshaft with strong overlap considering the reduction in power to low mode that that causes which is useful in the trails and forest roads of Quebec in the technical places where one must ride at low speed while asking the engine much

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578645 12/29/14 11:18 pm
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TG I do believe you have a problem and that you bike has suffered from detonation. No skeptic here!! I am not questioning that what you are hearing isn't detonation. I am just trying to point out to you some of the things I think you are over looking.

Here are some observations. I apologize if I am repeating myself:
If you are going to dual plug using a Boyer, Pazon or any EI with an advance curve engineered to suit a single plug application used on the street you are setting your self up for problems. The advance engineered for a dual plug installation will have a much shorter advance curve. The standard EI for A Triumph would retard the spark from 38° to approx. 14°. The same EI would retard the the spark from 20° BTDC to 4° ATDC. An EI engineered for a dual plug on a Triumph would retard the spark from 25° - 30° to 10° to 14° BTDC.

The hemi design of the Triumph cylinder head, with the top of the piston sticking right up into the combustion chamber, has a very slow combustion burn. You want the combustion to be at the end of its cycle at around 12°-15° ATDC. So for this to happen with a Triumph you need time for full combustion to take place so that is finished burning at the appropriate time

You can use a standard EI if your racing because the engine will hardly ever be below 3,500 rpm and the EI will always be fully advanced. This is not the case in the street, especially if you are fond of cruising and have installed tall gearing. Remember if you cruise, or accelerate under 3,000 rpm the timing isn't at 20° any more. It could be as low as 10° or lower.

Running an engine in a too retarded condition

Running 20° full advance on a single plug Triumph with either points or an EI will put the full retard timing at near TDC. There is no way this will work no matter how high the fuel octane is. The flame speed of this engine will not support this.

http://www.smokstak.com/forum/showthread.php?t=70385


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578646 12/29/14 11:21 pm
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But I do not like this kind of camshaft with strong overlap considering the reduction in power to low mode that that causes which is useful in the trails and forest roads of Quebec in the technical places where one must ride at low speed while asking the engine much


That is why they make 16 - 17 - 18 tooth sprockets.


Re: where do the coil wires go on dual plug heads? [Re: David Dunfey] #578648 12/30/14 12:10 am
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Originally Posted by David Dunfey
Kevin,

I did not realize that you were using such high octane. As John intimates, it may be the reason the combustion process is so slow. It is my understanding that you will produce the highest power using the lowest octane fuel that works with your compression ratio. Going lower or higher in octane will reduce the power.


i haven't always had access to gasoline that good. most of the time it's been with 91 or so unleaded premium, sometimes with lead substitutes added.

but i don't think i understand what you're saying about octane effects, and "getting the most power by using the lowest octane that will work with your compression ratio." are you tuning by varying octane number? that's a new idea for me. i've always tried to use fuel with an octane number high enough to eliminate it as a variable, and then do the actual tuning by changing the other stuff.

Originally Posted by David Dunfey

I am not sure what you are shooting for, but if you are looking for power, you need to optimize all these compromises that you are required to make.


i have a hot street bike that i want to make run as sharply as i can, physically and chemically, and still be useable at legal speeds, and hopefully not blow up. it's not a competition machine, just a long-term project. but i'm looking for ways to capture and analyze data on it, so lots of measurements are where my head is. i do have a competition machine in the works, though, so it all has a pretty sharp focus, in the end.

what i'm shooting for is understanding, really, and i'm most interested in understanding the british machines, because their level of technology and tuning is so fundamental.

Last edited by kevin; 12/30/14 12:31 am.

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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578658 12/30/14 1:44 am
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John

I ride my Triumph from 1974 to 1982 without problem, I even used pistons of 11.0:1 CR without hearing the least sound of knocking or pinking
I was seldom in bottoms of 100 Mph at the time considering which I was insane furious with my Triumph
My Triumph of origin with breaker-point adjusted at 38°, Lucas coil, Champion N3G spark-plug and front sprocket of 19 teeth
There was only gasoline with lead in Quebec before 1982, all went marvelously well and the engine turned easily to 7000 rpm

The nightmare started in 1982 with the arrival of the unleaded
Considering I had installed pistons 11.0:1 about 1981 and kept them with the arrival of the unleaded of 1982, I did not manage any more to hill climb the road without the engine wanting to be demolished by the knocking and the pinging
Then not the choice to install pistons of 9.0:1 like first test for eliminate the detonation.
But it was not sufficient, then about 1984 I moved back with 28° full-advance to cut a little more the detonation.
But it was not sufficient and taken discouragement I bought the Honda in 1986 considering which the only method to remove the detonation completely was one mix 50/50 with gasoline of plane

In 1992, I had the idea to again fight the problem of detonation by installing an Boyer with 2 coil 6V Lucas in series without large apparent change
When I installed modified the cylinder head of the engine for dual plug by cylinder towards 2002, I felt a small difference but not sufficient.
In 2006 I try the blow for Pazon Smart-Fire PD2TP adjusted at 28° without too much difference in behavior compared with Boyer Micro-Digital
In 2014, I found MY solution which is not can-to be not holds it but which is enough for me without being obliged to ride to the VP Racing or to use pistons 8.5:1
Simply of Torco Accelerator

About the full-advance, with each modification since 30 years I had tested between 20° and 38° and 25-28° are the ideal place not not to handicap the engine too much.

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578659 12/30/14 1:54 am
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Video of my Triumph in knocking mode

https://www.youtube.com/watch?v=24sa5PxAGCQ

towards 4m30s on this video and while climbing the small hill thereafter 14m50s
https://www.youtube.com/watch?v=-KEncRqPSrU


On this video I always ride to the threshold of the detonation with regular gas unleaded of AKI 85 at a cruising speed of 110-120 Km/h approximately at 1h20m00s
https://www.youtube.com/watch?v=Rc-96mIOfKM


I did not use Torco before 2014 wink

Last edited by Transgarp; 12/30/14 2:16 am.
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578696 12/30/14 10:49 am
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After looking at those video's I wonder what gearing are you using?

The only time I can select out pinging from general engine noise is when the engine is struggling.

Morgo always set-up those cylinders pretty loose. Is the engine noise worse when its cold or warming up?


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578702 12/30/14 11:35 am
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I use one 21 teeth what implies 4100 rpm in the 4th speed and 120 Km/h on the highway
I agree which it would be preferable a front sprocket smaller than 21 teeth for hill climb sand or abestos as at the time of the 2nd video one
But that returns expensive and tiring to ride on the highway or forest road to 4100 rpm for only 90 Km/h by using one 16 teeth
There are no gasoline station between Parent and LaTuque in Quebec for a distance of 200 kilometers and my tank of gasoline has only 12 liters
Then I do not have the choice to optimize the petrol consumption of the bike not to undergo a gasoline breakdown in middle of the night when full with wild beasts as the black bears grind in trimmings

The noise is really with timing
I am a mechanic of motorcycle Japanese and English for 40 years, then I have known and I must make the difference of the noises of engine to earn my living wink

I readjusted my last pistons Morgo .020" oversize with .008" because the engine had partially seizes when I had put it at .006"

The knocking arrives especially the summer when the weather is hot and that the engine functions since a certain time

The only time that I knew pinging is while returning from Parent at north of Quebec of the video last
The engine was seriously carbonized what had increased the ratio compression and had created hot spot to cause the pinging
Before 2012 I was accustomed to adding a little oil 2-cycle in the gasoline while thinking better of lubricating the combustion chamber
I ceased this useless practice after having dismounted the cylinder head and having decarbonized the pistons and the combustion chamber

This day there, I knew all the mechanical forms of musics. The pinging and the knocking


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578720 12/30/14 2:37 pm
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Kevin,

What I was meaning to say about octane is that in the crudest way, more octane is a bad thing because the higher the octane, the slower the burn. Of course, there is a situation where slowing down the burn rate is beneficial. This is when you increase the compression, which is the easiest way to get more power. The trick is matching the two.

So, I don't pick the octane as a tuning method, but I pick the fuel I will use for the season and tune for the octane rating of that fuel. If I choose 100 octane and all that is available at the track is 110 octane, the engine will most likely be down on power. Thus, it is as much a choice about availability as it is about performance.

If, for example, your pump gas is 93 octane, you could probably run a 12.5:1 CR piston without detonation. This assumes that your DCR (dynamic compression ratio) would be about 8:1 with lots of other considerations like sea level, humidity and temperature.

In general, the target DCR for pump gas is 8:1 plus a little, maybe plus .25, but if you use DCR it will be true for all the engines using DCR, single cylinder or v-8. You can't do this with the static CR figure that we are all familiar with because it is a purely theoretical number that will always be higher than the DCR by an unknown amount.

If I were running 110 octane I would think that I would be at 14:1 advertised CR with no detonation. So, I am curious about the mismatch.

I think your goal with the bike is laudable. It is a great challenge to get as much out of your engine as possible. When you begin to ask the questions that you are asking you realize that there is power in the engine for the taking if you can only find the right balance. The basis of all engine power begins with measurement, something I did not do enough of with my own endeavors.

Here are some DCR data that may be interesting:

http://purplesagetradingpost.com/sumner/techinfo/tech--dcr%20comb-sm-1.html

David

Re: where do the coil wires go on dual plug heads? [Re: David Dunfey] #578724 12/30/14 3:00 pm
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David, higher octane does not mean a slower burn..Octane effect on detonation is quite complex...I use racing fuel in my LSR Triumph and have spent time looking into what goes on...I'm not a fuel chemist so I have to believe what they say...
Here's some basics from Sunoco ...

High Octane

This is what I think a good explanation of detonation and preignition. And why the hole in your piston may not be from detonation. This may have been posted before and there are other opinions on this matter.

Ping ping


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: Hillbilly bike] #578738 12/30/14 4:21 pm
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Originally Posted by Hillbilly bike
David, higher octane does not mean a slower burn..


High octane fuels which I have used do burn slower than low octane fuels which I have used.

But you're right to say that the meaning of "high octane" is not "slow burning."


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Re: where do the coil wires go on dual plug heads? [Re: triton thrasher] #578747 12/30/14 5:29 pm
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Thank you both. I will defend myself by saying I did use the word "crudest", but I always appreciate learning more. I particularly liked the section on detonation caused pre-ignition!

David

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578785 12/30/14 10:28 pm
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well, i've followed these links on CR, and burning, and octane, and detonation. I've skimmed the links they link to, and looked at some of the links the links link to. and now i understand a great deal less than i thought i did when i started.

it seems as if DCR is a useful way to incorporate cam timing into compression ratio, generating a number that can be used with more predictive value than just static CR alone. but now i've got a lot more to think about.

my head hurts.

HB, this id from your link and seems similar to what david was suggesting earlier:

Quote
Production engines are optimized for the type or grade of fuel that the marketplace desires or offers. Engine designers use the term called MBT ( Minimum spark for Best Torque) for efficiency and maximum power; it is desirable to operate at MBT at all times. For example, let's pick a specific engine operating point, 4000 RPM, WOT, 98 kPa MAP. At that operating point with the engine on the dynamometer and using non-knocking fuel, we adjust the spark advance. There is going to be a point where the power is the greatest. Less spark than that, the power falls off, more spark advance than that, you don't get any additional power.

Now our engine was initially designed for premium fuel and was calibrated for 20 degrees of spark advance. Suppose we put regular fuel in the engine and it spark knocks at 20 degrees? We back off the timing down to 10 degrees to get the detonation to stop. It doesn't detonate any more, but with 10 degrees of spark retard, the engine is not optimized anymore. The engine now suffers about a 5-6 percent loss in torque output. That's an unacceptable situation To optimize for regular fuel engine designers will lower the compression ratio to allow an increase in the spark advance to MBT. The result, typically, is only a 1-2 percent torque loss by lowering the compression. This is a better trade-off. Engine test data determines how much compression an engine can have and run at the optimum spark advance.

For emphasis, the design compression ratio is adjusted to maximize efficiency/power on the available fuel. Many times in the aftermarket the opposite occurs. A compression ratio is "picked" and the end user tries to find good enough fuel and/or retards the spark to live with the situation...or suffers engine damage due to detonation.


point being, these folks are saying that once you have determined what spark advance is optimum for a given engine configuration/operating condition/benchmark, that any fuel change that results in detonation is better compensated for by reducing compression ratio than by retarding the spark.

but i's still lots easier to change timing than to change compression ratio, except by deciding in advance at the beginning of the season, as david suggests.

my head still hurts

Last edited by kevin; 12/31/14 11:41 am.

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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #578803 12/31/14 1:12 am
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After a score of 20 years to be ride with a cylinder head twin-plug by cylinder; I can say to you that that made pretty but not really necessary wink

Re: where do the coil wires go on dual plug heads? [Re: triton thrasher] #579359 01/04/15 8:50 am
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On the higher octane burning slower it seems there is no simple answer and it's a yes and no....
This is an explanation from a racer/ fuel chemist...A bit complex for my simple mind..


" You can have a higher octane fuel with any number of boiling points and igntion points. They have nothing to do with burning faster.

Fuel octane values (either RON or MON) have NOTHING to do with combustion flame speed. They are completely unrelated.

If we run an engine on the dyno using straight “isooctane” (224TriMethylPentane) it would have RON and MON values of 100. Interestingly, there are actually 18 different isomers for isooctane with different octane values.
We could then add measured amounts of Tetra Methyl Lead(TML) to increase the octane values in steps. We would find:

TML
g/gal ........ MON .......... RON
0 ........ 100 .......... 100
2 ........ 108.6 ........ 108.6
4 ........ 118.0 ........ 118.0
6 ........ 120.3 ........ 120.3

While the fuel octane values are increasing, there would be absolutely no change in engine performance or in ignition temperature, flame temperature, laminar flame speed, peak combustion pressure angle and total burn angle.

Fuel octane alone does not change these combustion values. But a change in blend composition is another matter. It is possible to have two fuel blends with the same octane numbers, but they will behave quite differently in the combustion chamber. This is due to the fuel blend components and not to their octane values.

Different fuel blend components do have a substantial effect on combustion properties.

..................................... nHeptane .... Methanol .... Toluene .... Isooctane

Laminar flame speed ................. 42.4 ....... 52.3 .......... 38.6 .........37.7
(cm/s)

A/F ratio for max FS .................. 122 ........ 101 ........... 105 ......... 106
(% of stoich)

Ignition temp ........................... 476 ........ 878 .......... 1052 ......... 874
(F)

Flame temp ............................ 3525 ........ 5050 ........ 3759 ........ 4193
(F)

Laminar flame speed is not affected by octane value but is a function of fuel blend components. Laminar flame speed is much too slow to burn properly in modern engines; chamber turbulence is necessary. When chamber turbulence (primarily squish velocity) is added to laminar flame speed, turbulent flame speed is the result. That is what will determine combustion burn angle, peak combustion pressure location, flame temperature and engine performance.

Laminar flame speeds are on the order of about 40cm/s (.4m/s). Squish velocity is on the order of 40m/s or about 100 times that of laminar flame speed. Combined turbulent flame speed would be 40.4m/s; the laminar flame speed having contributed very little to burn time or burn angle.

The ignition temperature of the fuel will determine the ignition delay period. The flame temperature of the fuel will affect the flame speed and combustion pressure.

It is most unfortunate that when race fuels are mentioned, even by fuel company marketing reps, octane seems to be the only fuel property that is mentioned. We very often find fuel company marketing reps to be very underinformed regarding their fuels. While every true race fuel refinery has fuel blenders and fuel chemists on staff, they are mostly kept out of sight and contact with race fuel customers. And the promotional literature is commonly written by some ad agency copy gal who knows only the buzz words and little else.

Fuel companies could provide real data regarding their products to help racers make the right decisions. But then, who would listen? frown "


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: Hillbilly bike] #579365 01/04/15 9:28 am
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Originally Posted by Hillbilly bike
Fuel companies could provide real data regarding their products to help racers make the right decisions. But then, who would listen? frown "

Yep wink

Re: where do the coil wires go on dual plug heads? [Re: Hillbilly bike] #579568 01/05/15 4:10 pm
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well, this is interesting, tony

Originally Posted by Hillbilly bike
. . .
While the fuel octane values are increasing, there would be absolutely no change in engine performance or in ignition temperature, flame temperature, laminar flame speed, peak combustion pressure angle and total burn angle.


what exactly is it in tetraethyl lead that retards knock? how does it work, if octane value and flame speed aren't necessarily related? is it all about suppressing pressure-ignition?

Quote
Fuel octane alone does not change these combustion values. But a change in blend composition is another matter. It is possible to have two fuel blends with the same octane numbers, but they will behave quite differently in the combustion chamber. This is due to the fuel blend components and not to their octane values.


^^^this is not encouraging.


every day you do not take a chance is a day of your life that you will never get back.
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579612 01/05/15 10:27 pm
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Kevin,

I don't want to attempt to explain the chemical properties of lead, but it did replace MBTE, which was carcinogenic, and MBTE was replaced by ethanol, another octane booster, so to speak. You say correctly that the increase in octane effectively increases the pressure under which the intake charge will ignite. Thus, with low octane fuel, the intake charge will self ignite under high compression. So, the major cure is to increase the octane or lower the compression. Once your are close to the correct compression/octane combination you can fine tune by adjusting the timing.

Higher octane fuels can burn both faster or slower and this usually depends upon the blend as well as the architecture of the molecules. But, this should not matter to you, yet, and in general the flame propagation is usually quite similar at different octanes.

As HB points out, the "slower burning" characterization probably says to much even though it is true in certain instances. I think this has also become a popular characterization because high octane fuels can be "slower" to ignite under the same pressure as low octane fuels even if the flame propagation is equal.

If you think about the ethanol as increasing octane, you may also realize that ethanol has less energy than an equal amount of gasoline without ethanol. This can be a problem with running higher octane fuels. It does not automatically translate into higher energy that is available to push your piston down harder.

So, if you want more performance from your engine the object should be to match your compression ratio to the best fuel at the closest gas station. You don't even have to do the engineering. Just use the DCR that every motorcycle manufacturer uses: about 8.2:1. Then go to the dyno and set your timing. You should then have the best power that you can expect from your motor with the accepted inputs.

The process will be more involved for a race engine, but measuring and matching components and inputs should be the foundation for the work.

David

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579645 01/06/15 7:34 am
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Originally Posted by Kevin
. . .

what exactly is it in tetraethyl lead that retards knock? how does it work, if octane value and flame speed aren't necessarily related? is it all about suppressing pressure-ignition?

Here's what I read....
Quote
The anti-knocking agents reduce the activity of free radicals in the burning mixture, either by eliminating them, or by converting them to radicals that are relatively stable (and thus unreactive).

Burning proceeds as a chain reaction mediated by free radicals. If the radicals are unstable, the reaction is fast, and less heat is needed to initiate it. Branched alkanes (isooctane) and aromatic compounds produce relatively stable radicals which allow the chain reaction to die down. Tetraethyl lead eliminates free radicals by allowing them to combine with its ethyl groups.



Here's the thread I started on Speedtalk, a site populated by professional racers and engine builders,fuel chemists and so on...There's some good info and of course some pure opinion...
Octane


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Re: where do the coil wires go on dual plug heads? [Re: David Dunfey] #579742 01/06/15 10:40 pm
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Originally Posted by David Dunfey

So, if you want more performance from your engine the object should be to match your compression ratio to the best fuel at the closest gas station. You don't even have to do the engineering. Just use the DCR that every motorcycle manufacturer uses: about 8.2:1. Then go to the dyno and set your timing. You should then have the best power that you can expect from your motor with the accepted inputs.


well, i've gone through the DCR calculator from your link (lots of other information in there as well), and it appears that there are some physical measurements i need to do on that head first. luckily, it's apart at the moment, so i'll see what i can do. regarding fuel, i've got access to that 110 leaded premium, and also to ordinary 93 unleaded. when the snow melts i'll try out both of them and see what timing works best. i'm very curious about the results of switching the inner coil leads, because that would seem to make the biggest difference, from what i've read here.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579754 01/07/15 12:27 am
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damn, i hate losing stuff i typed. short version:

HB, have you encountered situations in tuning where the spark timing could be advanced until horsepower began to fall, without going into detonation first? any engine.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579766 01/07/15 8:00 am
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Yes,my 650 race Triumph. 10.5 compression using 107 octane leaded race fuel. And many years ago with "muscle cars" using 260 Sunoco pump gas.
Disclaimer, short periods of full throttle high rpm detonation can go unnoticed in more robust engine designs.Detonation in V-8 powered circle track race cars causes excessive bearing wear or even cracked cylinder walls and a lesser experienced racer might just think the engine block is defective.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: Hillbilly bike] #579849 01/07/15 11:00 pm
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that's been my impression from what people say, in that detonation-limited engines seem to be more gasoline-quality-limited engines. holding the gas quality constant, reducing compression ratio but holding the advance seems to keep the most horsepower. (this is theoretical. i haven't done it).

not being able to hear detonation is a problem with loud pipes. i've been trying to learn about exhaust gas temperature, and it seems that it can reflect detonation that you might not be able to hear by showing a sudden decrease in temperature, as that extra heat goes into the piston and head, rather than the exhaust.

innovate sells one that can be linked to a data logger:

[Linked Image]


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Re: where do the coil wires go on dual plug heads? [Re: NickL] #579878 01/08/15 8:55 am
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Nick,the operator of the dyno shop I use for the race bike has a very simply mechanical device to detect detonation. A short length of a small diameter copper tubing is mechanically fastened to the engine head. it's connected with rubber tubing to a set of "headphones" just like a doctor's stethoscope.The sound of detonation can be heard clearly over the normal engine clatter.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579890 01/08/15 11:34 am
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that's a really useful suggestion.

kevin cameron once wrote that detonation sounded like smacking rocks together underwater, hard. i've heard that in my motor before using poor quality gasoline in an emergency, but the continuous knock that you can't hear because of pipes and concentration would be extremely useful to detect.

there's too many variables to keep track of it all if you're running a motor at the edge, especially fuel blending.



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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579904 01/08/15 12:48 pm
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And piezoresistive chips are used to plot cylinder pressure under varying loads. But all of this is theory and the problems I see day-in-day and day-out are more of a practical nature. As Kevin Cameron is fond of saying, you must toughen you engine to prevent detonation and pre-ignition long before your offer fuel to the engine. The first thoughts about detonation should be in the workshop, not the gas station or the dyno room. It is way to late to make any meaningful changes.

Unlike BSA and Norton, who have by some measure almost modern combustion chambers, Triumph's hemi combustion chamber design was abandoned by engine designers years ago. It is a relic from the distant past. The design is further inhibited being air cooled, very minimal in mass and with no where adequate fining for what some people expect from the engine.

While static compression and intake cam closing are a starting point they are just that.
Just as important are:
• Valve margin thickness, margin shape and seat widths.
• Removing all sharp edges from the piston, spark plug hole, and blending valve pockets.
• Selection of the proper grade of spark plug.
• Selecting cams, and timing those cams, with the intended use in mind.
• Of course timing and fuel mixture.
• Matching individual gear ratios and overall gear ratios for the engines power band and intended use. There is a reason Triumph provided wide ratio transmissions on their dual-purpose models.
• Selecting piston ring thickness that matches the engine design. Thin rinshould not be ones first choice for street engines using pump gasoline.
• Making sure rings seat during initial start-up as 75%, or more of the heat in the piston is removed through the rings. Those low tension thin rings have there place, but it is not always in one of these motors.
• The over all gear ratios are matched to the intended use and riders ability. There is a reason Triumph provided wide ratio transmissions on their dual-purpose models.
• And while those early light flywheels worked well for the likes of Eddie Mulder on the soft sand, they provided more opportunity for combustion mischief with the novice rider. At low rpm they lack the kinetic energy

There is a lot of talk about squish and "swirl" helping control detonation. You also hear talk about about squish this, and squish that about Triumph heads. While there might be flat areas near the edge of some Triumph pistons and heads are thought to be squish bands the only head that comes near having a true squish band is the early unit 500 twin. And although the physical parts are in place, the gap between the piston and head is such that it is a squish band in name only. It is too wide to be effective. If you are not measuring and setting the gap in the .035" range it is of no benefit in creating enough swirl to help control detonation.

In the end Triumph did two things that were an effort to help prevent detonation, but it was very late coming. The T140D head with the parallel ports and the constant velocity carburetor. The T140D port design dramatically increased swirl improving combustion and lowered combustion temperatures to a point where it required running spark plugs 2 ranges hotter to prevent fouling. The CV carburetors prevented high dynamic cylinder pressures caused by rapid opening of the carburetor while the engine is under even a light load (often referred to as lugging).

Before Triumph started to use the CV carb the rider had to remember to shift to a lower gear when he sensed that the bike did not respond with an increase in speed as the throttle was opened. While your car does this without you thinking about it, with your Triumph you have to remember to do this. And when you sort the motor a lot of the detonation, and even modern engines designed to use current fuels will detonate, can be managed with intelligent use of the throttle and the shift lever. Modern cars have a computer... your Triumph only has you.


Re: where do the coil wires go on dual plug heads? [Re: John Healy] #579916 01/08/15 1:42 pm
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Originally Posted by John Healy
And piezoresistive chips are used to plot cylinder pressure under varying loads. But all of this is theory and the problems I see day-in-day and day-out are more of a practical nature. As Kevin Cameron is fond of saying, you must toughen you engine to prevent detonation and pre-ignition long before your offer fuel to the engine. The first thoughts about detonation should be in the workshop, not the gas station or the dyno room. It is way to late to make any meaningful changes.


In my opinion you have to be on guard for detonation when testing on an engine on the track or in the dyno room.Especially hobbyist builders like me who don't have years of experience on a Triumph engine to know the limits.
All might be fine with the engine build but a bad or mislabeled fuel load could turn the pistons inside out....

Last edited by Hillbilly bike; 01/08/15 1:43 pm.

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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579937 01/08/15 3:46 pm
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Quote
All might be fine with the engine build but a bad or mislabeled fuel load could turn the pistons inside out....


I am not totally unfamiliar with detonation! But over some 50 years of preparing Triumph engines for racing of all sorts, I have learned not to wait, but to anticipate these kinds of problems. Most of the failures I personally have experienced have been of my lack of understanding, not the fuel's.

And my post was not inspired by your previous post...

This is where I like to start:
[Linked Image]
These are the piston blanks we use when setting up an early 500 squish band head so it works.


Re: where do the coil wires go on dual plug heads? [Re: John Healy] #579939 01/08/15 3:51 pm
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Originally Posted by John Healy

There is a lot of talk about squish and "swirl" helping control detonation. You also hear talk about about squish this, and squish that about Triumph heads. While there might be flat areas near the edge of some Triumph pistons and heads are thought to be squish bands the only head that comes near having a true squish band is the early unit 500 twin.


hi john

i'm used to seeing much better squish bands on old two-stroke cylinder heads than i've ever seen in a triumph. i didn't even recognize one being there the first time i looked.

are there modifications that one can do to a stock triumph T120 head that can significantly increase swirl? maybe my question includes increasing velocity in general, as it seems to me that one would help the other.


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Re: where do the coil wires go on dual plug heads? [Re: John Healy] #579942 01/08/15 4:17 pm
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JH,I saw that photo of yours recently and meant to ask...Why are the rings located so far below the piston crown ? It appears the they be moved up quite a bit before fouling the valve relief. All modern piston designs seems to have the ring package pushed up as high as possible to eliminate unburned gases remained in the 'dead space"

[Linked Image]


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579946 01/08/15 4:50 pm
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I don't think the rings can go much higher, when you look at the complicated shape of the crown.


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Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579947 01/08/15 4:53 pm
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are there modifications that one can do to a stock triumph T120 head that can significantly increase swirl? maybe my question includes increasing velocity in general, as it seems to me that one would help the other.


No, the 650 head, or the late 500 for that matter, does not lead itself to having a squish band without a lot of work, and expense. The 750 twin can be worked to have a squish, but requires different pistons and some work.

Increasing air velocity through the ports seems counter intuitive. Because drawing air into the cylinder is a timed event, air velocity is more than a consideration. In a lot of tuner's eys it is where a lot of the magic comes from. The common thought is to increase the port diameter, but in my experience with the 650 it is too big for a street engine to start with. For street work the early 9 bolt head with the small non-unit ports and valves makes for a more useable, easy to tune, and more rideable street bike with a good wide power range suitable for the standard 4 speed gearbox.

The same port as the late 650 works real well with the large bore of the short rod 750. Unless you know exactly what you are doing I would leave the ports alone, but concentrate your time and money to the area around the valve seat.


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579951 01/08/15 5:15 pm
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JH,I saw that photo of yours recently and meant to ask...


They are blanks - you chuck them up and machine them to match the squish band in the head. The final shape, after some nibbling away the parts I don't need, is not unlike the ones the factory used in the T100 and Triple racers.

As the area under the dome is also not machined you can vary the top of the dome for improved flame propagation and final compression ratio. You need to put them in a piston vice and go at them in the Bridgeport. This also allows you to vary the piston weight to fine tune balance.


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579985 01/08/15 8:53 pm
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No, Nick no misunderstanding here. And they also have sensors to measure dynamic cylinder pressure under no-load and full-load. These can be used to predict abnormal cylinder pressures that can lead to detonation.


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #579997 01/08/15 9:48 pm
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I worked the squish in a different way. Instead of squishing around the edge of the piston into the centre, I put the squish opposite the spark plug so the charge is pushed around to the plug. No detonation problems with this on pump fuel.
[Linked Image]

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #580012 01/08/15 11:56 pm
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Triton Because of the size of the valve cutaway on the intake side of this piston if the rings aren't set a bit lower than normal the valve pocket cuts right into the ring groove. Not ideal, but it seems to work out. Except for the valve pockets the whole dome of the piston above the ring grooves is solid when I get the pistons. The head is machined and measured and the dome cut to match. Then the inside is cut leaving a dome thickness in the range of .125". Do the same with the 750 we ran for years.

David - Nice "another way to skin the cat." KB pistons have been making a piston for sportsters with a similar dome configuration for quite a few years now. It is a whole new world when you find out you can get partially finished pistons and match the pistons dome to the head. SOme people create a trough across the top of the pistons in an effort to improve combustion. Still some small signs of detonation. It seems you exercised the throttle some, or were beginning to loose a valve spring, with that right cylinder exhaust valve kissing the piston - was it worth it? DId you win...


Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #580013 01/09/15 12:44 am
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That was probably when I was following an RG500 with my Wenco framed R3 racer on PCH coming back south from Laguna Seca. He could not out accelerate me coming out of the corners. If the throttle cable doesn't need adjustment periodically you're not turning hard enough, yes?

Last edited by DMadigan; 01/09/15 2:33 am.
Re: where do the coil wires go on dual plug heads? [Re: John Healy] #580089 01/09/15 2:17 pm
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The T140D head with the parallel ports and the constant velocity carburetor. The T140D port design dramatically increased swirl improving combustion and lowered combustion temperatures to a point where it required running spark plugs 2 ranges hotter to prevent fouling.

hi John, very interesting info as ever.
But I still cannot understand how you can have "improved combustion" and lower temperature at the same time? Is it because they had a very lean carburation and very low CR?







Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #580111 01/09/15 4:32 pm
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Simply stated - the swirl from the incoming mixture seems to mix the air/fuel mixture better than the "splay port" resulting in a better burn or "improved combustion" = little or no detonation.

no-detonation = lower combustion chamber temperatures - and the "explosion" isn't pushing past (blowing away) the protective boundary layer that insulates the head from the heat of combustion.

With lower compression, which they had already done in previous years, you compress the incoming charge less. As a result the fuel air mixture does not heat up as much as it did with a higher compression. It is all a balance of controlling pressure in an effort to control heat. You want the fuel/air charge to burn and not explode.

The constant velocity carb prevents the rider from taking a handful of throttle at low rpm. Doing so, you can drive the dynamic cylinder pressure, and gas temperature with it, to the point that when the spark plug fires the additional pressure created by combustion pushes the end gas (un-burnt gas opposite flame front) to a point where it will self ignite. You have just created a case of severe detonation. In a CV carb the slide responds to manifold vacuum, and not just to throttle position and prevents the rider from causing the carburetor from delivering a big gulp of air when it cannot handle the dramatic increase in cylinder pressure it causes.

A good example of this is checking the cylinder pressure with a gauge. Leave the throttle closed and you get a very low reading - There is no air through the carburetor to compress. Open the throttle and the engine takes that big gulp and the needle jumps up over 100 pound and more. That is dynamic cylinder pressure - it changes with slide position.


Re: where do the coil wires go on dual plug heads? [Re: John Healy] #581391 01/17/15 2:57 pm
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Originally Posted by John Healy
Simply stated - the swirl from the incoming mixture seems to mix the air/fuel mixture better than the "splay port" resulting in a better burn or "improved combustion" = little or no detonation.

no-detonation = lower combustion chamber temperatures - and the "explosion" isn't pushing past (blowing away) the protective boundary layer that insulates the head from the heat of combustion.

With lower compression, which they had already done in previous years, you compress the incoming charge less. As a result the fuel air mixture does not heat up as much as it did with a higher compression. It is all a balance of controlling pressure in an effort to control heat. You want the fuel/air charge to burn and not explode.

The constant velocity carb prevents the rider from taking a handful of throttle at low rpm. Doing so, you can drive the dynamic cylinder pressure, and gas temperature with it, to the point that when the spark plug fires the additional pressure created by combustion pushes the end gas (un-burnt gas opposite flame front) to a point where it will self ignite. You have just created a case of severe detonation. In a CV carb the slide responds to manifold vacuum, and not just to throttle position and prevents the rider from causing the carburetor from delivering a big gulp of air when it cannot handle the dramatic increase in cylinder pressure it causes.

A good example of this is checking the cylinder pressure with a gauge. Leave the throttle closed and you get a very low reading - There is no air through the carburetor to compress. Open the throttle and the engine takes that big gulp and the needle jumps up over 100 pound and more. That is dynamic cylinder pressure - it changes with slide position.
I get a great education when I examine some of these discussions. Taking this in a slightly different direction, It seems that most if not all the comments here apply to highly modified machines. I am no stranger to mixing fuels to reach necessary octane levels.My 1969 BSA owners handbook shows a minimum octane requirement of 98 ( I'm thinking RON) for a stock 9:1 A65. HB provided two good links,the Sunoco one I am familiar with. The other brought out something that seems to be lost on some people-that a slightly lower static compression ratio with a factory engineered timing curve is better than a retarded timing curve with high(er) compression ratios and is the better way to get our old -stock- iron to run on 91-93 octane pump premium.The article mentioned a 1 to 2% loss in torque with lowered compression. Didn't the majority of T140's have an advertised compression ratio of 7.9:1 in preparation for lower octane unleaded and the phasing out of super premium leaded fuel? With A65's or T120's I was never satisfied with the performance of retarded timing so as to operate on sub-standard fuel.The engine is so much happier with 100 octane and the factory settings and so am I.SO my question is, would quality forged pistons-not cheap- that provide a lowered 8:1 compression ratio for otherwise stock A65,T120,etc. machines be marketable, and if not why not? Hoping for a lot of feedback.


1969 BSA A65T w/A70 engine
1970 Royal Enfield Interceptor S ll
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #581392 01/17/15 3:07 pm
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My 76 T140V at 7.9/1 would run on lamp oil


When given the choice between two evils I picked the one I haven't tried before
Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #670447 10/08/16 9:26 am
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Transgarp calling John Healy smile

I dismantling the engine of the T120R in May
According to this Web site, the wear of my conn-rod bearing confirms the detonation caused by a gasoline of too low octane or a too high C.R., here 9.5:1 with 750 Morgo kit
http://www.agkits.com/bearing-failure-analysis.aspx

My bearing wear:
http://transgarp.dyndns.org/motorcycle/0800/20160000/20160521_04.JPG

The last year 2015, I ride under this configuration :
750 Morgo kit CR 9.5:1
28° full-advance
21 teeth front sprocket, 46 rear
Detonation

In August 2016 I reassembled the engine with this configuration :
750 Routt kit CR 8.9:1
38° full advance
22 teeth front sprocket, 46 rear
No detonation

All my problems of detonation disappeared, while riding with the same super gasoline of Shell and more power all rpm smile

You surely wonder why I have enlarges the front sprocket.
Not the choice because of the necessary release of the chains to the top of the front of the swingarm considering which I installed the complete back suspension of a Honda XR650L on the frame of the T120R

http://transgarp.dyndns.org/motorcycle/2000/20161001/17.JPG

http://transgarp.dyndns.org/motorcycle/2000/20161001/08.JPG

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #673622 11/06/16 2:32 pm
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What do you know, I have an A65 that has the primary side rod brgs that look just like that. Spitting image. However, I have no information on the motor or how it ran when it was a complete bike. I know it had under 10,000 miles on it and the throws and bush are factory clearances. I assume it was all stock. It is a 1971 engine and everything else is specking out as should be. Maybe it had some bad spark knock hey? detonation? I don't know, but I have never seen a brg look like that except in books. I have seen automotive engines like a big block Chevy that was ran very hard at high speeds for several miles then shut down right afterwards and had a slight knock in the morning after cool off, when torn apart one rod or rather one rod with the bearings must have been to hot at shut off and stuck to crank, when it was disassembled it looked similar to what you have. No harm to rod or crank, could only figure one defective bearing that lost its integrity and stuck to crank. Reassembled and fine good to go. Sometimes you do even get defective parts from factory, I know this BSA engine has never been apart so maybe a bad one. Ive seen several bearing failures from vandervill in the past 25 years.

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #675272 11/22/16 10:42 pm
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Not sure if the original post and original questions are still relevant. But to respond, my AHRMA road racer T140 engine has 11.5:1 pistons, has a twin plug head done many years ago at John Healy's suggestion by Dana Johnson at Import Machine Service in Mass., and uses a crank-driven twin plug ignition I got from Rex Caunt (modified PVL with little twin lead coils). When I first did this, I used a Boyer Powerbox, and John Healy suggested to me to place each of the two wires from each coil on opposite cylinders to get better spark, and I have continued to do that, it seems to work the best that way. To answer the other questions I saw above, I use 32 degree fork lead, and 110 race gas. The effect has been to make the engine run cooler and smoother and make more torque--the combustion chamber shape and flame front were obviously issues with a single plug and this very high compression. Runs great! Doubt twin-plugging is necessary on the street with 9:1 or so, though.

Re: where do the coil wires go on dual plug heads? [Re: kevin roberts] #678816 12/24/16 3:29 pm
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i twin-plugged my old street bike when all i could get was 89 unleaded. these days i use 110 leaded premium and run the timing back to 30 BTDC.

i'm running 11.75:1 now on another machine that is single-plugged at the moment, because i'm using an old ARD. but i'm using VP 108 C12 in it

http://www.racefuel.com/vp-c12-racing-fuel-108-octane/


every day you do not take a chance is a day of your life that you will never get back.
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