Ive been tuning the tables on my car with the 148 ecm, 3.5" maf and translator

I have the car running way better than what i started with, I am using a scanmaster and wideband to figure out which air flow I am at and a/f ratio

I am noticing something strange though

Under load with a given Gm/s reading, I have one afr

and then if i am at say a lower LV8 but the same air flow, i have another AFR.

It seems like its anywhere from .5 to 1.0 afr point leaner under load, am I on crack or what? Or does this have a perfectly logical explanation?


another thing I was wondering is if the gm/s displayed is the number I put in the chip or is the GM/s display extrapolated from counts somehow and remains constant relative to the counts?
I ask because, lets say I put numbers that calculate to 5.6, 5.9, and 6.4 in three consecutive cells in the maf table, will I just be displayed 6 for all three cells?

Im guessing yes... and that makes tuning difficult without direct scan which I am getting soon anyway I hope

Thanks for any help

 

Timing can have a big effect on indicated AFRs. I dunno about a fuel 1.0 thou. I've never seen that much.

The ecm rounds off it's calculations.

 

Could be a problem with the "Injector turn-on time" or in other words the "offset vs Vbatt" giving problems. If the PW and frequency of injections are different (i.e. different load and RPM but same Airflow as you say), then this is what is needed to bring the two points to the same A/F.

 

I'm not certain how "Scanmaster" works, but I would suspect that the data you are seeing is AFTER the raw MAF input is translated by your scale tables. The only way to be sure is to monitor the raw MAF data/voltage. You could experiment by "wasting" a PROM and setting the MAF scales to something ridiculous, and seeing if the scanned data reacts accordingly or reports something more realistic. I'd suspect the former.