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AFR Tuning - question about power vs different AFRs

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I saw that in the webinar where you did 3 back to back pulls on 3 different lambda values and it didn't produce a much different result, but I do have a subquestion regarding that. but I'll divide it in two

1. Flame speed changes at different lambda values - shouldn't we then "to prove a point" - be trying to re-check for best ignition timing? Or is the same power level at 3 different levels proof enough that in reality, the correct ignition timing is about the same regardless of lambda values?

2. often on very knock limited cars (Mitsubishi Evo 8 peak torque timing in this example running 1.6bar boost on a car running just a 3" decat exhaust) - I have found that by richening the mixture for example even to 0.75 produced a better result because I was able to run about 4 degrees of timing at ~3500 RPM while at lambda 0.80 I was only able to run 2 degrees. It made about 15Nm torque difference. Reducing boost produced much worse results. How would you tune it in a case like this?

Yes combustion speed will change with AFR however for the purposes of this demonstration, we are only considering AFR. This goes with the myth/misconception that you're going to see maximum power at the leanest AFR and doesn't really consider timing.

Yes, in many instances a richer AFR will cool the combustion charge sufficiently to allow the timing to be advanced further and hence we often see additional power as a result. This is discussed at some length in our understanding AFR course and is yet one more example of why you can't hope to blindly apply the same lambda target to every engine and call it 'job done'. You need to test and find out what your specific engine combination responds best to. This is more relevant in knock limited engines, but it's an important aspect people overlook.

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