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Lean hot start

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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when I start the car after been driving for a while. It’s lean for a minute or so.

My guess is the air sensor is heat socked because it’s in the intake manifold. Sow it’s uses the iat compensation table which takes out 6% fuel at 60 degrees.

Am I right ?

Or is there a setting which i didn’t setup?

Link g4+

r53 turbo conversion (1000cc injectors which are to big for the low load/rev conditions)

Yes, a combination of a slow responding heat soaked IAT sensor and hot fuel rail would be the main contributors to the lean hot start. The easiest option is to set up your IAT trim table with TP on one axis and either add a little fuel (or remove less) at high IAT and small TP's. An example below. You can get more sophisticated and do it more like an OEM strategy if you like with a 4D fuel table based on say engine running time and IAT etc but typically the basic IAT table like below is all you need.

Hi Adam,

thanks for the fast reply,

i made a similar table only the X axis is setup to engine running time. it worked great (its very hot right now)

the iat at hot start is around 70 degrees and i added 6% after 200 seconds of driving its back to normale

i understand it affects the base tune, so i have to drive not to hard untill the 200 seconds are over.

or is this a bad way ? as i thought the sensor give sensible reading after those 200 seconds.