Topic: How to Calculate Advance Ignition Timing?

[scottly]

on the dyno, seek the least advance that still give you best peak torque, this will ensure that engine runs coolest as it'll be working against the least negative work.

john reynolds calls it MBT, minimum advance best torque

Interesting, I would have optimized full advance for best peak HP? I wonder how much difference between the two? Testing for peak torque would certainly be easier on the equipment, due to the lower RPM.
Dave, remember that the dyno is for finding full advance, and not initial or "idle" advance. In a nutshell, if the initial is too little, the motor will be hard to start, like it has low compression. The electric starter will spin the motor freely, and it will fire, but not quite want to catch and run. If the initial is too advanced, the engine will buck against the starter.   

[turboguzzi]

tuning for peak torque is due to the fact that at this rpm point volumetric efficiency is best, i.e. cyl is the fullest with charge, so most prone to detonation.

am using john robinson's words/explanation here, but makes perfect sense to me.

[DaveBarbier]

on the dyno, seek the least advance that still give you best peak torque, this will ensure that engine runs coolest as it'll be working against the least negative work.

john reynolds calls it MBT, minimum advance best torque

Interesting, I would have optimized full advance for best peak HP? I wonder how much difference between the two? Testing for peak torque would certainly be easier on the equipment, due to the lower RPM.
Dave, remember that the dyno is for finding full advance, and not initial or "idle" advance. In a nutshell, if the initial is too little, the motor will be hard to start, like it has low compression. The electric starter will spin the motor freely, and it will fire, but not quite want to catch and run. If the initial is too advanced, the engine will buck against the starter.

Got it, thanks Scottly. As of now I don’t think I run the risk of either of those scenarios. I’ve already been too advanced where power was dropping off and the bike still fired up normally. Also I was retarded where power was dropping off and it also started fine. So I’m going to be in between there somewhere. I do hope that it holds a steadier idle. I know I know that idle doesn’t matter, blah blah blah, I feel Dave500 is going to get his spider sense activated when I say that...but I want it to be a stable idle that’s 1500 or lower. It’s quieter, smoother and over all gives better engine braking. After I get the advanced dialed in I might play around with the plate for idle and see which gives the smoothest, lowest idle. Then I might try to modify the advance mechanism to give both best power and best idle. Might take some grinding of the cetrifugal weight stops.

[DaveBarbier]

tuning for peak torque is due to the fact that at this rpm point volumetric efficiency is best, i.e. cyl is the fullest with charge, so most prone to detonation.

am using john robinson's words/explanation here, but makes perfect sense to me.

So at the dyno I’m going to do my normal runs and if I see in one ignition plate position I have, for example, 40lb/ft and 70hp and in another position I have 42lb/ft and 68hp I’ll keep it at the second one. Right? These numbers are hypothetical of course.

[DaveBarbier]

Ended up checking where I had set the advance to when I was out on my ride. I retarded it by 2.5° so I’m at 36° total advance. I’ll retard it a bit more to 34° and see how it feels tomorrow. Then hopefully dyno Friday to test.

[scottly]

Ended up checking where I had set the advance to when I was out on my ride. I retarded it by 2.5° so I’m at 36° total advance. I’ll retard it a bit more to 34° and see how it feels tomorrow. Then hopefully dyno Friday to test.

That is 46* total!??

[DaveBarbier]

Ended up checking where I had set the advance to when I was out on my ride. I retarded it by 2.5° so I’m at 36° total advance. I’ll retard it a bit more to 34° and see how it feels tomorrow. Then hopefully dyno Friday to test.

That is 46* total!??

So wait...this is exactly what I was saying above and why I made this post in the first place. Yes, it says 46 total. When I set it to the factory advance hash marks my degree wheel says 38.5° but the book says total advance is 28.5°. TDC on the advancer lines up with the 0 on my degree wheel and the idle setting lines up with 10° on the degree wheel, just as the book says.

I feel like I’m repeating myself...haha!

[scottly]

10* initial+ 28.5* of centrifugal advance = 38.5 TOTAL advance. With the setting of 46* on the wheel, where are the full advance marks on the stock advancer?

[DaveBarbier]

10* initial+ 28.5* of centrifugal advance = 38.5 TOTAL advance. With the setting of 46* on the wheel, where are the full advance marks on the stock advancer?

Full advance marks are just to the left of the witness mark on the case. Well, like 7.5° to the left

I’ve posted this before but want to be a little clearer on my process.
Ok so when I first set up the Dyna, I used the stock settings. It ran but had reduced power. Then Paul from C5 told me that his ignition has 10° idle and 40° advance. I wasn’t sure if that 40° was centrifugal or total so I tested it. I advanced it even further up to 48.5° (10°+40°=50°. When I was at the dyno a few weeks back (when I still had the C5) we gained a couple hp by retarding the ignition a couple degrees. So if the stock C5 is 40° we probably retarded it to 38°, that’s why I set it 48.5°. Then I went out for my ride and still had reduced power. I retarded it a bit more to 46° and gained noticeable power. Then last night I retarded it a bit MORE to 44° and have yet to ride it to see if it’s better or worse.

Hope that makes sense!

If my degree wheel says 46° in the picture, should call it 36° advance? Like if someone asks what my advance is, do I say 36° or 46°? It’s very confusing! When I first set up my degree wheel and saw 38.5° instead of the 28.5° that was in the FSM I was like...whaaaatt? And to make it worse, the manual says 28.5° BTDC! That’s wrong, it’s not 28.5° before top dead center, it’s 28.5° before idle. Which means 38.5° BTDC!

[turboguzzi]

the words from the man itself

[DaveBarbier]

the words from the man itself

Ah that’s interesting that he’s talking about doing it live on the dyno. Thanks for sharing, I saved this picture.

[scottly]

10* initial+ 28.5* of centrifugal advance = 38.5 TOTAL advance. With the setting of 46* on the wheel, where are the full advance marks on the stock advancer?

Full advance marks are just to the left of the witness mark on the case. Well, like 7.5° to the left

I’ve posted this before but want to be a little clearer on my process.
Ok so when I first set up the Dyna, I used the stock settings. It ran but had reduced power. Then Paul from C5 told me that his ignition has 10° idle and 40° advance. I wasn’t sure if that 40° was centrifugal or total so I tested it. I advanced it even further up to 48.5° (10°+40°=50°. When I was at the dyno a few weeks back (when I still had the C5) we gained a couple hp by retarding the ignition a couple degrees. So if the stock C5 is 40° we probably retarded it to 38°, that’s why I set it 48.5°. Then I went out for my ride and still had reduced power. I retarded it a bit more to 46° and gained noticeable power. Then last night I retarded it a bit MORE to 44° and have yet to ride it to see if it’s better or worse.

Hope that makes sense!

If my degree wheel says 46° in the picture, should call it 36° advance? Like if someone asks what my advance is, do I say 36° or 46°? It’s very confusing! When I first set up my degree wheel and saw 38.5° instead of the 28.5° that was in the FSM I was like...whaaaatt? And to make it worse, the manual says 28.5° BTDC! That’s wrong, it’s not 28.5° before top dead center, it’s 28.5° before idle. Which means 38.5° BTDC!

My head hurts. Set the #$%*ing timing at the stock 650 full advance marks with a strobe. This will be 38-40* BTC. Verify this is for both 1-4 and 2-3. Scribe a reference mark on the plate and case, so you have a baseline. From here, try adjusting the timing, and note the effect.

[PeWe]

I had my K6 ignition correctly set, I thought. Dyno run where I was not happy with the power.
I tried to advance the entire point plate just a little, like 2-3mm on the plate's outer edge where I had marker pen lines to case. Result, less hp.
Another adjustment to the other side of the first marked postion, 2-3 mm retarded. Better got 2 Hp.

Practical tests on Dyno with max power to be achieved despite retarding until power reduce, go back then.. ? No need of measure degrees just change and see Dyno result. When best is done, maybe measure to remember how this very engine want it.
Ignition is dependent on compression and shape of the pistons vs combustion chambers right?

[DaveBarbier]

10* initial+ 28.5* of centrifugal advance = 38.5 TOTAL advance. With the setting of 46* on the wheel, where are the full advance marks on the stock advancer?

Full advance marks are just to the left of the witness mark on the case. Well, like 7.5° to the left

I’ve posted this before but want to be a little clearer on my process.
Ok so when I first set up the Dyna, I used the stock settings. It ran but had reduced power. Then Paul from C5 told me that his ignition has 10° idle and 40° advance. I wasn’t sure if that 40° was centrifugal or total so I tested it. I advanced it even further up to 48.5° (10°+40°=50°. When I was at the dyno a few weeks back (when I still had the C5) we gained a couple hp by retarding the ignition a couple degrees. So if the stock C5 is 40° we probably retarded it to 38°, that’s why I set it 48.5°. Then I went out for my ride and still had reduced power. I retarded it a bit more to 46° and gained noticeable power. Then last night I retarded it a bit MORE to 44° and have yet to ride it to see if it’s better or worse.

Hope that makes sense!

If my degree wheel says 46° in the picture, should call it 36° advance? Like if someone asks what my advance is, do I say 36° or 46°? It’s very confusing! When I first set up my degree wheel and saw 38.5° instead of the 28.5° that was in the FSM I was like...whaaaatt? And to make it worse, the manual says 28.5° BTDC! That’s wrong, it’s not 28.5° before top dead center, it’s 28.5° before idle. Which means 38.5° BTDC!

My head hurts. Set the #$%*ing timing at the stock 650 full advance marks with a strobe. This will be 38-40* BTC. Verify this is for both 1-4 and 2-3. Scribe a reference mark on the plate and case, so you have a baseline. From here, try adjusting the timing, and note the effect.

Mine too, from beer though. As of now the bike pulls pretty well and I’m at 44° which is 5.5° advanced from stock. Stock is 38.5° BTDC (again, even though the book says it’s 28.5° BTDC but that has to be a typo). But ok, I’ll set back to stock setting and work from there at the dyno.

[DaveBarbier]

I had my K6 ignition correctly set, I thought. Dyno run where I was not happy with the power.
I tried to advance the entire point plate just a little, like 2-3mm on the plate's outer edge where I had marker pen lines to case. Result, less hp.
Another adjustment to the other side of the first marked postion, 2-3 mm retarded. Better got 2 Hp.

Practical tests on Dyno with max power to be achieved despite retarding until power reduce, go back then.. ? No need of measure degrees just change and see Dyno result. When best is done, maybe measure to remember how this very engine want it.
Ignition is dependent on compression and shape of the pistons vs combustion chambers right?

Agreed.

[PeWe]

Only one small "problem". Dyno time.
It would be easier if having access to one when needed for not much $$

[DaveBarbier]

Only one small "problem". Dyno time.
It would be easier if having access to one when needed for not much $$

Dyno near me charges...I forget...like $50 for three pulls. One reason why I’m trying to use the old butt dyno to get close so hopefully I’ll spend less time there.

[turboguzzi]

there are good android apps that extrapolate quite well HP from acceleration/speed runs in public roads just using your smartphone

even if the numbers might be off compared to a rwhp dyno, they can help you see if you improved or not.

some of the parameters to enter will have to be guessed, like Cd, but still, if its to compare ignition settings between runs it could be useful

just find a quiet and flat piece of road...

https://www.perfexpert-app.com/

https://www.team-bhp.com/forum/technical-stuff/184500-perfexpert-app-poor-mans-dyno.html

[DaveBarbier]

there are good android apps that extrapolate quite well HP from acceleration/speed runs in public roads just using your smartphone

even if the numbers might be off compared to a rwhp dyno, they can help you see if you improved or not.

some of the parameters to enter will have to be guessed, like Cd, but still, if its to compare ignition settings between runs it could be useful

just find a quiet and flat piece of road...

https://www.perfexpert-app.com/

https://www.team-bhp.com/forum/technical-stuff/184500-perfexpert-app-poor-mans-dyno.html

I’ll look into it. PerfExpert also has an iPhone app. But calculating or guessing coefficient of drag...that seems unlikely. BUT if I’m not looking for actual horsepower numbers but rather only looking for an increase or decrease in hp it could work. Would have to really have optimal conditions though. Consistent wind, flat horizontal road, same throttle pull...

[turboguzzi]

well, do opposite direction too for each measuremnt...
as for throttle, just like you do on the dyno, go up to 3000 and from then wide open.

[Rod]

Reading this thread, I can't help thinking back to advice my Father (ace tuner & mechanic) gave when I once suggested we did a dyno session, he told me 'kid, we've already got the two instruments we need, your backside & my stopwatch'.

[Rod]

Reading this thread, I can't help thinking back to advice my Father (ace tuner & mechanic) gave when I once suggested we did a dyno session to sort out a new carb setup & ignition system, he told me 'kid, we've already got the two instruments we need, your backside & my stopwatch'.

[DaveBarbier]

Reading this thread, I can't help thinking back to advice my Father (ace tuner & mechanic) gave when I once suggested we did a dyno session to sort out a new carb setup & ignition system, he told me 'kid, we've already got the two instruments we need, your backside & my stopwatch'.

While I love that, technology and computers have made tuning carbs and ignition better even on these old machines. Having put a lot of money into this project (too much, let’s be honest) I feel I’m doing myself a disservice if I don’t try and get every ounce of power out of this mini monster.

[PeWe]

One important setting is the needles easy found on Dyno with A/F meter. Or if you have an  mounted on your bike.
I got my TMR needles found way too rich and later verified again on another Dyno.
Dyno guy slowly increased the thotlkes from 2000-6000 rpm. Very rich. This opened my eyes for it so I could learn what it was. Lowered them 1 step, still not clean run, one step more and it ran fine. Dyno verified that later.
I'm currently in the pilot part increasing it to make engine to run even at take offs and really slow city speed. Compensate with too rich fuel screws is not good. Stinking too rich at idle and the very first area over idle.

Verify main jets at close to top speed is a little bit dangerous on common roads

[DaveBarbier]

Got back from some dyno time this afternoon. I was very close so my butt dyno is pretty accurate! I’m currently at 36.5° total advance. Which is weirdly close to the stock setting and when I was at the stock setting earlier it felt low on power...not sure why, probably because I’m crazy. But who cares, ignition is done and I’m happy. Bike pulls very nice!

I retarded it from about 40° to 36.5° and gained about 2 hp and about 1.5lb/ft of torque (not huge but that was not really the goal today). I was looking at torque and it increased the more I retarded it and then it leveled off and started to drop.