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E50 Stoich

EFI Tuning Fundamentals

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Hi Andre

If i wanted my car to idle on E50 what AFR should I be aiming for? Looking at the pdf from the previous module, 9 for Ethanol and 14.7 for pump gas would it be the difference between these two values? Ie (9+14.7)/2 = 11.85AFR. Or would i still be aiming for 14.7 as with normal pump gas?

Forget AFR, use Lambda -- Lambda 1.0 is always stoich for the fuel. If your O2 wideband is calibrated for gasoline at 14.7 AFR, then just make it ready 14.7, and you will be at Lambda 1.0 -- the real AFR won't be 14.7, but since the Lambda will be 1.0, it will be the correct value.

As david said, makes it MUCH easier to learn to just use lambda, that is always the base value the AFRs are calculated from.

As it is, I suspect you're over-thinking it - most AFR guages/meters actually work with lambda and convert that value to what the petrol/gasoline AFR value would be to give that lambda. So, at stoich' for any fuel the lambda should be 1.0 and the guage will read 14.7. Some guages have provision for changing fuel type, but that last is actually a potentially dangerous problem, as if the fuel isn't exactly what it's set to (classic is tanks not draining fully when changing fuels, contaminating the fresh mix), the actual AFR may be different from the guage, but the lambda will always be correct.