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Fuel Quality and Octane Degree and AFR

EFI Tuning Fundamentals

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Discussion and questions related to the course EFI Tuning Fundamentals

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does quality and Octane degree of Fuel change the AFR, low quality fuel needs to make it reacher in whole table ?

and does stoichiometry of low quality fuel is different?

It depends on the details. If you have lower octane fuel in areas that tend to knock, you will need to run richer or to retard spark. In areas that aren't limited by knock it won't matter much, like idle. Another formulation that matters is how well the fuel vaporizes. The blend of the fuel changes depending on the season, and that can affect starting a bit. In the summer the fuel tends to make less vapor, which is better for emissions but worse for starting. So summer style fuel in winter conditions can be hard to start, and might need richer fueling to prevent it from stalling. Usually you put a safety factor in your cold start tuning so you don't run into that problem.

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