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air temp compensation

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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HI there

Still trying to get my head around this table. As you say as air temp increases you ajust the table to have less fuel in a cell at increasing temp. I'm confused as I thought you would increase the fuel supply as air temp is increasing as combustion temps must be increasing. So wouldn't increasing fuel be a good idea, to decrease the temp to a better level to help reduce knock and produce more power?

Hotter air is less dense, which in turn means it has less oxygen and you will run richer if you dont compensate for that in the IAT. Also warmer air vaporizes fuel better, hence with a cold start you add fuel and taper off as chamber and intake manifold warms up. You need to find what IAT your engine is comfortable running at and above those temps you can ADD fuel if you are experiencing mild knock to help cool the combustion chamber, so you dont damage the car on a hot summer day for example.

The air temp compensation discussed is aiming to maintain a consistent AFR as air temp fluctuates. This may not be what you want to do however and as you suggest, often adding some additional fuel as air temp increases can have benefits on an engine that is heavily knock limited.