MAF Calibration Questions for my 95 LT1

Hey all,

Just up front, I do know what I am doing in calibrating MAFs. I have done it for years and confirmed my prior Hawk engine, with its calibrated MAF, was correct. In that situation, I had to modify the MAF by -12% on the idle side to adding 9% more on the WOT side (meaning it was lean in WOT area before calibration). Reference this sticky to confirm my background: http://www.camaroz28.com/forums/showthread.php?t=505190

Here is the deal: my current RX7 conversion with the 95 LT1 setup shows the correct calibration requires a reduction of 28.5% from the stock tables to on the WOT end (100 AFGS and up) to get my BLM's to 128 range and eliminate the rich condition I had.

Bottom line, this does not seem right with a reduction of 28.5% in the tables! However the car runs fantastic and makes great power. Injector DC's are reading about where they should and further, the BLM's are equal on each bank. They only thing I can conclude is the heads are more efficient and thus burn more oxygen which shows up as a rich condition with the O2's. I had calibrated this MAF prior when the engine was still a 350 stock headed LT1 and the calibration at that time indicated a 9% reduction at WOT.

Just looking for input...

Ben

Well, are you shooting for the WOT A/F ratio that is programmed in? In other words, at WOT the AF is set richer than normal, and if you used BLMs as an indicator, and changed MAF to get to 128, you would be at stoic instead of the desired rich condition. That could take a pretty big change to the MAF table. If I understand correctly - I have only cal'd my MAF for non-wot conditions.

I appreciate you taking a shot at this.

I disable PE mode while tuning the MAF so I am at stoich throughout the entire range. I want to shoot for 128 in all BLM's (and I am very close at 127 in the upper end of the MAF tables). Your note regarding PE mode WOT is not an issue here.

Different fuel injectors?

BLMs can be affected by a lot of fuel-related things like injector offset, base pulse width, extra pulse width adder, etc. They may show up in a non-linear fashion too.

Different fuel injectors?

BLMs can be affected by a lot of fuel-related things like injector offset, base pulse width, extra pulse width adder, etc. They may show up in a non-linear fashion too.

Interesting. No idea if the guy I bought the car from used aftermarket injectors but I will be looking at this closely when I put in my new injectors in the coming weeks.

Thanks for giving me something more to consider.

i thought that if you are in pe mode the ecm only reads off of the last blm it see's if the car is running lean so if you blm in cell 15 is 140 it is going to add a certian percent of fuel i believe some where around nine percent before it adds the fuel from the pe tables so you would have a pe fuel ratio of 12.1 plus 9 percent for example so the car becomes pig rich. I know my new blms are around 133 all of the time now and the car has no knock with the pe table set to about 12.5. this is on stock timing with 93 octane. The car runs very good and my gas milage went up when i got my blms from 144 to 133. also on my pe table i just subtracted fuel equal across the board in the pe vs rpm table and it seems to work for me.