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Ignition Timing Question

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Hi Andre question about tuning ignition timing on knock limited pump gas,

If we are knocking at 5000 rpm and 15 psi do we lowered the timing for just that cell or do we have to lower entire map to smooth out everything? For example if 5000 rpm 14 psi isn't not knocking but due to 5000 RPM 15psi knock do I have to decrease that too?

If i don't decrease timing in the lower load i find them to have lot of repeating value is that ok to do or do i must make sure the timing is alwlays going lower and lower when hitting higher load when going wot?

Hello Jinu0808, it is not Andre it is Léo ahah :)

Physically, the more cylinder air mass there is, the less advance you have to calibrate to be at knock limit.

First, be careful to your axis, twice as much boost don't always mean twice as much cylinder air mass.

Secondly, due to some phenomenon, for a same rev sometimes you can have the same advance to be at knock limit for a different air mass.

There is not one way to do : you can calibrate from exactly what you see in response or smooth maps.

Got it thanks Leo

You want to optimise each zone in the ignition table as far as possible, so if you find you need to retard the timing at 5000 rpm and 15 psi only, this doesn't mean you need to retard the entire map.

Generally a well tuned ignition table is going to show a relatively smooth and consistent shape - If it looks like a mountain range then I'd be questioning its accuracy. You will also find that the engine will be most knock prone around peak torque as this is where the air mass in the cylinder is greatest. It's common to retard the timing around peak torque before advancing it again as rpm increases.

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