As many people know using an AFC with large injectors sucks due to the AFC not really controlling "fuel" but more-so cheating the MAF into thinking less airflow. My problem is I am leaned out to about -38% across the board which has got to be advancing the timing way too much. I had an idea but not sure how much it will help. My idea is to retard the base timing a few degrees. How much will this actually help? How much should I retard it? Also, on DSM's I know you need to ground something on the firewall to adjust the base timing... do I need to do this on an Evo as well?

 

The Cam and Crank angle sensors are fixed, meaning you can't change the base timing easily.

Your original premise is incorrect however, so there is no problem, and it is only an advantage that it doesn't retard the timing as much with the larger injectors.

I question your -38 settings though unless you are running 1200cc injectors. You should really tune it with a datalogger to get the fuel trims right and the air fuel ratio consistent across the RPM range.

 

I politely disagree

By leaning the car out using an AFC by that much will make the ECU advance timing; it does not think there is nearly as much air going into the motor than there really is, thus advancing timing. I am using a wideband logger. It is at -38%. I have not hooked up my pos datalogger to it but I will once I get the tranny back in and make sure the fuel trims are close. At WOT I am hitting around 11:1 so I am positive it is fine at the -36% range (At least for the WOT tuning). As for the low fuel settings, It has to be alot closer to the -36% than nothing at all. I think the injectors are mathematically around 40% larger but there is alot more than straight size (Dead time, etc...) but I assume that the -36% low must be relatively close.

 

^ put the lo throttle settings at 0 unless you can use an obd2 logger to see what the ecu is backing out. Give it a try. It works trust me.