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Fuel base map


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Hi guys. I’m new to efi tuning but do have lots of tuning experience with carby/dizzy stuff. I’ve been looking through my pcm tables from my na fg and noticed the fuel base table auF0172 has some quite rich lambda settings stock. 
Is this the only fuel map that dictates the target afr for each load/rpm point? 
it appears to be. 

will changing the figures in this map directly change my afr or is there another map that can change it aswell and therefor end up with a different afr to what I put in this table ? 

Any insight is appreciated. 

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This is correct, assuming injectors are stock and the car has no modifications that would affect VE (eg standard turbo, standard camshafts) then you should be able to simply change the commanded lambda to affect the fueling.

If you have started modifying things and you find the commanded lambda does not match the measured lambda via your wideband. Then you need to start modifying the fueling (injector slopes) and airflow (speed density) models.

If you have modified the vehicle then read the following forum threads. 

Injector slope scaling:



Speed Density


Open Loop / Closed Loop Fueling

You need to be aware that these engines only have closed loop fueling at stoichmetric 1.0 lambda. Eg at idle/cruise. Outside of these conditions the engine runs open loop. That means if anything changes (eg fuel pump runs out of flow, you change the VE of the engine eg camshafts ) the car will no longer run the commanded AFR and you will need to correct the mechanical issue or modify the appropriate model in the software (eg injector fueling model or airflow speed density model).

If you are a workshop then we can point you in the direction of someone who can provide paid training. Otherwise the best way is to post on the forums and read all the HOWTO Guides.

I also recommend purchasing a wideband and an analog input cable so you can datalog your actual AFR vs your commanded AFR. Once you have tested this on the street you need a dyno to test it safely at wide open throttle. There are many dyno operators who will hire out there dyno at a per hour rate, there are even some mobile dyno operators who will come to you.


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