Ignition Advance at Idle?
Discussion
Interesting, thanks chaps.
Next two questions:
1. What is your chosen target AFR at idle?
2. How stable is your AFR at idle?
To make answering point 2 simpler, what are your typical numerical fluctuations IE the high/low numbers you see either side of your target AFR at idle ?
Thanks, Dave.
Next two questions:
1. What is your chosen target AFR at idle?
2. How stable is your AFR at idle?
To make answering point 2 simpler, what are your typical numerical fluctuations IE the high/low numbers you see either side of your target AFR at idle ?
Thanks, Dave.
Around 13.0 give or take .5 either side Dave I idle slightly rich in AFR terms as on idle my dynamic CR is s
te and the whole engine config at these speeds is far from ideal (not surprising) running Alpha N is far more stable at low speeds than MAP/speed density based with a lumpy cam, MAP/SD which I presume you are using is better if you can get away with it 
why use 2D when you can run 3D
te and the whole engine config at these speeds is far from ideal (not surprising) running Alpha N is far more stable at low speeds than MAP/speed density based with a lumpy cam, MAP/SD which I presume you are using is better if you can get away with it why use 2D when you can run 3D 
Sardonicus said:
Around 13.0 give or take .5 either side Dave I idle slightly rich in AFR terms as on idle my dynamic CR is ste and the whole engine config at these speeds is far from ideal (not surprising) running Alpha N is far more stable at low speeds than MAP/speed density based with a lumpy cam, MAP/SD which I presume you are using is better if you can get away with it why use 2D when you can run 3D
Thanks Simon, and there are indeed clear differences in our engines, to be clear I run a Stealth cam and being the original engine, the standard compression ratio. te and the whole engine config at these speeds is far from ideal (not surprising) running Alpha N is far more stable at low speeds than MAP/speed density based with a lumpy cam, MAP/SD which I presume you are using is better if you can get away with it why use 2D when you can run 3D Using the principle of "give the engine what it wants" I'm idling at 950rpm at 13.7:1 AFR but surprisingly it seems happiest like this with 23 degrees of advance which really shocked me? This is on petrol, on LPG I actually run 3 degrees less timing at idle but a lot more from there on, all this again using the principle of "give the engine what it wants".
The AFR at 13.7:1 is perfectly in line with my expectations but none of these trends in ignition timing at idle are exactly what I'd expect, 23 degrees seems like a lot of advance to me at a 950rpm idle? But the engine, its idle quality and my ears don't lie, its definitely happier running these figures, starts better too.
Your thoughts and comments on the above are welcomed
ChimpOnGas said:
Thanks Simon, and there are indeed clear differences in our engines, to be clear I run a Stealth cam and being the original engine, the standard compression ratio.
Using the principle of "give the engine what it wants" I'm idling at 950rpm at 13.7:1 AFR but surprisingly it seems happiest like this with 23 degrees of advance which really shocked me? This is on petrol, on LPG I actually run 3 degrees less timing at idle but a lot more from there on, all this again using the principle of "give the engine what it wants".
The AFR at 13.7:1 is perfectly in line with my expectations but none of these trends in ignition timing at idle are exactly what I'd expect, 23 degrees seems like a lot of advance to me at a 950rpm idle? But the engine, its idle quality and my ears don't lie, its definitely happier running these figures, starts better too.
Your thoughts and comments on the above are welcomed
That rings true Dave I was running around this with the stock motor too but any more than this with the new motor makes the revs hang at anything over 22 and inconsistent at running temp Using the principle of "give the engine what it wants" I'm idling at 950rpm at 13.7:1 AFR but surprisingly it seems happiest like this with 23 degrees of advance which really shocked me? This is on petrol, on LPG I actually run 3 degrees less timing at idle but a lot more from there on, all this again using the principle of "give the engine what it wants".
The AFR at 13.7:1 is perfectly in line with my expectations but none of these trends in ignition timing at idle are exactly what I'd expect, 23 degrees seems like a lot of advance to me at a 950rpm idle? But the engine, its idle quality and my ears don't lie, its definitely happier running these figures, starts better too.
Your thoughts and comments on the above are welcomed
Sardonicus said:
hat rings true Dave I was running around this with the stock motor too but any more than this with the new motor makes the revs hang at anything over 22 and inconsistent at running temp
Brilliant mate, that puts my mind at rest, in my case I could see the EGTs increase over the 23 degree point but like the AFR they are very stable and safe at the 23 degree figure.As I experimented by advancing the timing one degree at a time the sweet spot came at a much higher figure than I ever could have expected (23 degrees). The Canems closed loop idle seems amazingly effective at mitigating the natural increase in idle speed you might ordinarily expect from adding what in the end amounted to a full five degrees of timing at a 950rpm idle
The engine continues to idle at the 950rpm target but soooo much sweeter its like night and day, the AFR is massively more stable so much so at one point I thought my AEM X-Wifi had stuck at 13.7:1, until that is I looked at the Canems software which showed exactly the same figure and lack of fluctuation. The engine starts even better with improved throttle response just off idle too, all in all it took a surprising amount of advance but the engine clearly loves it.
The other thing that amazed me was how I could adjust the AFR by just making timing changes, as I walked the timing up a degree at a time the AFR got nearer and nearer to my closed loop AFR target until I landed at 13.7:1, at which point the engine ran like a turbine!
Like the oldun days I could clearly hear the engine reach it's sweet spot just as easily as I could see the AFR hit the target on my new world of tuning laptop, the results were genuinely as surprising as they were a profound improvement in every way. And all this on a TVR I always felt ran way sweeter than most and achieved by simply eliminating a few minor vacuum leaks on the crankcase breather hoses and by adding some timing.
Very happy
ChimpOnGas said:
Brilliant mate, that puts my mind at rest, in my case I could see the EGTs increase over the 23 degree point but like the AFR they are very stable and safe at the 23 degree figure.
As I experimented by advancing the timing one degree at a time the sweet spot came at a much higher figure than I ever could have expected (23 degrees). The Canems closed loop idle seems amazingly effective at mitigating the natural increase in idle speed you might ordinarily expect from adding what in the end amounted to a full five degrees of timing at a 950rpm idle
The engine continues to idle at the 950rpm target but soooo much sweeter its like night and day, the AFR is massively more stable so much so at one point I thought my AEM X-Wifi had stuck at 13.7:1, until that is I looked at the Canems software which showed exactly the same figure and lack of fluctuation. The engine starts even better with improved throttle response just off idle too, all in all it took a surprising amount of advance but the engine clearly loves it.
The other thing that amazed me was how I could adjust the AFR by just making timing changes, as I walked the timing up a degree at a time the AFR got nearer and nearer to my closed loop AFR target until I landed at 13.7:1, at which point the engine ran like a turbine!
Like the oldun days I could clearly hear the engine reach it's sweet spot just as easily as I could see the AFR hit the target on my new world of tuning laptop, the results were genuinely as surprising as they were a profound improvement in every way. And all this on a TVR I always felt ran way sweeter than most and achieved by simply eliminating a few minor vacuum leaks on the crankcase breather hoses and by adding some timing.
Very happy
Nice results Dave As I experimented by advancing the timing one degree at a time the sweet spot came at a much higher figure than I ever could have expected (23 degrees). The Canems closed loop idle seems amazingly effective at mitigating the natural increase in idle speed you might ordinarily expect from adding what in the end amounted to a full five degrees of timing at a 950rpm idle
The engine continues to idle at the 950rpm target but soooo much sweeter its like night and day, the AFR is massively more stable so much so at one point I thought my AEM X-Wifi had stuck at 13.7:1, until that is I looked at the Canems software which showed exactly the same figure and lack of fluctuation. The engine starts even better with improved throttle response just off idle too, all in all it took a surprising amount of advance but the engine clearly loves it.
The other thing that amazed me was how I could adjust the AFR by just making timing changes, as I walked the timing up a degree at a time the AFR got nearer and nearer to my closed loop AFR target until I landed at 13.7:1, at which point the engine ran like a turbine!
Like the oldun days I could clearly hear the engine reach it's sweet spot just as easily as I could see the AFR hit the target on my new world of tuning laptop, the results were genuinely as surprising as they were a profound improvement in every way. And all this on a TVR I always felt ran way sweeter than most and achieved by simply eliminating a few minor vacuum leaks on the crankcase breather hoses and by adding some timing.
Very happy
I tend to run open loop on idle as things seem f a i r l y consistent and I'm being lazy with setting up closed loop idle 
but will have a go with the new system when I eventually get my full seq inj up and running just dont hold ya breath 
still bench faffing with it at the moment before it goes on the car but thats another story Edited by Sardonicus on Wednesday 16th November 09:54
BoostedChim said:
Do you gys have any issues when releasing the throttle and letting it fall back to idle? I found when running higher advance timinings mine was less inclined to return to idle, it would sit around 1300rpm.
Yep done that too like I say in one of my previous post hence why I settled on 18 BTDC and no more 
BoostedChim said:
Do you gys have any issues when releasing the throttle and letting it fall back to idle? I found when running higher advance timinings mine was less inclined to return to idle, it would sit around 1300rpm.
No issues like that so far with the new 23 degrees idle setting, it still seems like a heap of advance to me but I can't argue with the super sweet way she ticks over.I'll keep you posted with the hanging idle thing, my Canems is running closed loop idle (CLI) so will always look to achieve the 950rpm target, not sure why the RPMs would hang with the extra advance but maybe they would without my CLI?
If it helps I can turn CLI off and see what happens?
ChimpOnGas said:
No issues like that so far with the new 23 degrees idle setting, it still seems like a heap of advance to me but I can't argue with the super sweet way she ticks over.....
Are you sure the markings are correct on the pulley?Reason I say this is that the front pulley is a harmonic damper and is in two parts. The parts are bonded together with rubber (not unlike a OE suspension bush). What can happen is the bond breaks down and the two parts rotate relative to each other with the result the timing marks are wrong.
As well as the timing marks being wrong the damper will have been drilled to balance the engine so if it has moved the engine will now be out of balance.
Ask me how I know.... Found this after having taken the whole of the front of the engine apart again thinking I had somehow screwed up timing a new cam.
Steve
Steve_D said:
Are you sure the markings are correct on the pulley?
Reason I say this is that the front pulley is a harmonic damper and is in two parts. The parts are bonded together with rubber (not unlike a OE suspension bush). What can happen is the bond breaks down and the two parts rotate relative to each other with the result the timing marks are wrong.
As well as the timing marks being wrong the damper will have been drilled to balance the engine so if it has moved the engine will now be out of balance.
Ask me how I know.... Found this after having taken the whole of the front of the engine apart again thinking I had somehow screwed up timing a new cam.
Steve
Pulley?Reason I say this is that the front pulley is a harmonic damper and is in two parts. The parts are bonded together with rubber (not unlike a OE suspension bush). What can happen is the bond breaks down and the two parts rotate relative to each other with the result the timing marks are wrong.
As well as the timing marks being wrong the damper will have been drilled to balance the engine so if it has moved the engine will now be out of balance.
Ask me how I know.... Found this after having taken the whole of the front of the engine apart again thinking I had somehow screwed up timing a new cam.
Steve
I haven't used my strobe or looked at the pulley for years mate.
All that (and the distributor) was replaced with this...
And this....
ChimpOnGas said:
Pulley?
I haven't used my strobe or looked at the pulley for years mate.
All that (and the distributor) was replaced with this...
......
I may be wrong but suspect all of your trigger wheel arrangement bolts onto the front of the harmonic damper in which case all I'm saying is are you confident your trigger wheel is still correctly aligned to true TDC.I haven't used my strobe or looked at the pulley for years mate.
All that (and the distributor) was replaced with this...
......
Steve
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