Darth_V8r

iTrader: (4)

This is for my 2004 suburban - trying a shot at doing this myself from stock.

The truck is stock, except for a LS6 cam (I know, I know) and a melling oil pump. 192,000 miles on truck, 40K on the motor.

I faulted out the MAF to force SD mode and begin logging for VE, and the truck immediately ran better. So, I cleaned the MAF and put it back in MAF mode with no change, and then bought a new MAF with no change. Always pulls harder and uses less gas (according to mpg calculator on the dash) in SD.

So, other than MAF calibration, which will just have to wait until the VE is finished, is there anything else I should look for that would cause the truck to run better in SD vs MAF?

I know I could just leave it in SD, but I would like to understand the why of it and use the MAF like it is designed. Purely an educational experiment.

Darth_V8r

iTrader: (4)

FYI, MAF is screened, fully intact

2xLS1

iTrader: (25)

It's common knowledge you make a bazillion more HP in SD than with a MAF.

joecar

Are you going to correct the MAF...?

Darth_V8r

iTrader: (4)

Yes. I'm going to leave the MPVI in the truck and drive it for about a week and get several logs and make sure the VE table is right. Then, yes, I'll take a shot at the MAF calibration.

gagliano7

I would say your maf is making it run rich. I am sure once you tune the maf you will be good.

http://www.hptuners.com/forum/showth...096#post121096 I like this for tuning the maf very simple and works great.

MontecarloDrag

iTrader: (3)

Datalog the truck running SD then again in MAF mode. Compare both runs and find how much gas/timing is commanding, then adjust.
You should get the same power with either SD or MAF

Darth_V8r

iTrader: (4)

Good call on that. I just pulled some logs off my MPVI last night, and the SD fuel trims were running -9 to -15 across the board. I know that you typically read "do the multiply by %-half" feature, but since I was averaging a few logs into one big adjustment, I multiplied the average by .75 instead of half.

Logging it some more today. My dashboard readout is already 1-mpg higher than it was, and that's on 20 miles of city driving.

That was what I thought - I should get the same performance. Once I get the VE's staying closer to zero, I'll re-enable the MAF and start logging it.

joecar

+1 on g7's post, MAF tuning is simple, any VE is filtered out by the transient filter.

Darth_V8r

iTrader: (4)

This is going to sound laughable, but on a suburban, this is a big change.

I was getting 12.7 mpg. Still logging and fine tuning SD, but I'm at 14.9-15.0 now. City driving for both numbers.

Wife even commented on how much smoother it runs.

Should have bought HPT three years ago