PE enabled, but not activating (0411 8322)

[Fast355]

I'd like to point this above right on post out. The MAF meter is probably almost 20 years old. 90% of the new/rebuilt ones are sometimes worse than the dirty/coated one you take off. There is no reason EVER to have to alter the transfer function of that MAF in the calibration. Are we smarter than GM on this transfer function? That type enclosed MAF with screens is dead nuts and reliable till it gets dirty or typical age ozone and dust coated. The only ones you can buy that seem to be correct are the AC-Delco and Delphi NEW maf's, not the rebuilt junk at NAPA, Oreilly's, Autozone, etc. You said you have a stock engine so unless you made changes to alter the VE(exhaust, cam, porting, etc), your VE table should be pretty right on too. Best thing to do to start is turn off VE and get it to run correctly on just the stock MAF settings.
I am not talking about cartridge MAF's and how they are critical to inlet ducting and any change in that can cause a lot of grief.

LRT has been very kind to help you, chasing failing or just bad equipment doesn't help anyone.

Good luck,
-Carl

If that is true...
Why does GM have different MAF transfer tables for the very same MAF in different applications? The LT1s are different F-car vs Corvette LT1 vs Corvette LT4. The Vortec trucks are different than the Vortec vans. The 350 vans have 2 different MAF tables depending on which airbox they used too. The 4.8/5.3/6.0L trucks are different than a LS6 Corvette too. I think GM calibrates the MAF transfer for the airbox they used with the MAF. For example, ALL 2002 V8 gas powered vans had the same MAF and airbox. The 305, 350 and 8.1 all used the same MAF transfer except around idle.

I know my Express van ran like crap on a 2002 Express van MAF table using the 97 airbox and ducting. When I swapped to the later ducting and airbox it was still off. I had a good clean OEM MAF and a new smaller body Delco MAF that they sell to replace the larger LT1/Vortec MAF. Same results with both. Camshaft seems to really effect fueling up to about 30-50 gms/sec. First thing I do is disable the MAF and tune the VE. Then I disable the VE and tune the MAF. Even on stock setups they are usually pretty far off the mark.

[In-Tech]

I am not talking about the garbage 3 wire maf in the early stuff or the 3 wire used in the 0411 express.

[In-Tech]

The 07+ 5 wire is not the same animal either. Continue on, I'll be quiet.

[Fast355]

The 07+ 5 wire is not the same animal either. Continue on, I'll be quiet.

I would like to hear more on what you have to say.

Just have seen variations in that same 85mm 5 wire MAF you are talking about in various GM applications.

As I mentioned a 2003 Tahoe 5.3 has a vastly different MAF transfer table than a 2004 LS6 Corvette. The Corvette MAF table is my go to calibration for startup for LS swaps with the MAF connected to the throttle body via a short straight intake tube. If you run the stock truck MAF table I have seen MAF codes with that setup and the fueling is way off. The problem is compunded when people put a short silicone hose off the throttle body and a cone filter on the MAF.

[In-Tech]

I would like to hear more on what you have to say.

Just have seen variations in that same 85mm 5 wire MAF you are talking about in various GM applications.

As I mentioned a 2003 Tahoe 5.3 has a vastly different MAF transfer table than a 2004 LS6 Corvette. The Corvette MAF table is my go to calibration for startup for LS swaps with the MAF connected to the throttle body via a short straight intake tube. If you run the stock truck MAF table I have seen MAF codes with that setup and the fueling is way off. The problem is compunded when people put a short silicone hose off the throttle body and a cone filter on the MAF.

Yes, you are correct. The Corvette and the GTO each have different transfer functions but completely different intake tube tracts. We are still dealing with an '01 truck aren't we? That's all I am getting at. As soon as I look at a tune that others have been in. My first look is at the MAF table and if others have been in there I just throw it away and start from stock. The ford guys used to have no choice cuz theirs was friggin horrible, any change and it was fubar so it's normally ford guys who jump right into the maf table first.

[Fast355]

Yes, you are correct. The Corvette and the GTO each have different transfer functions but completely different intake tube tracts. We are still dealing with an '01 truck aren't we? That's all I am getting at. As soon as I look at a tune that others have been in. My first look is at the MAF table and if others have been in there I just throw it away and start from stock. The ford guys used to have no choice cuz theirs was friggin horrible, any change and it was fubar so it's normally ford guys who jump right into the maf table first.

01 truck with a non-stock intake tract.

[woody80z28]

01 truck with a non-stock intake tract.

Yup. This and this. Not exotic, but not stock. The tube is 4in diameter, and the MAF is about 3.5 if I remember correctly.

[woody80z28]

Ok, I cleaned the MAF really well and double checked for unmetered air leaks. (No leaks and the MAF looked pretty damn clean, but it did change my AFR a bit after the cleaning.) However, what I really noticed was the angle of the tube right after the MAF. It has a much more noticeable bend than you really see while installed in the truck. I wouldn't be surprised if that skews the sensor readings.

The intake was an ebay special for "2500HD" but it turns out it's for 4.8/5.3/6.0 and I had to modify it a bit to fit 8.1. Unfortunately, I already tossed the stock stuff so I can't do a sanity check on the sensor.

What I did see though, was the idle was high 11s until the LTFT hit 80 and STFT hit 95. So that's pulling out 25% to hit 14.7 right? Steady state low throttle at 2000ish rpm the LTFT was about 90-92. WOT was 100 LTFT and 13.0-13.2 AFR. So math-wise it seems like the calibration is non-linear.

So I'm going to disable the MAF, take a log and make sure my VE tables are pretty good with a historygram. Once I'm happy with the VE tables, I'm thinking of adding 6% to the stock MAF curve, re-enabling and taking a look at the LTFT historygram again.

Then, will I be able to use LTFT in a newly built historygram of RPM vs g/sec to tune in the MAF? Since I can't get the wideband to report to the datastream, I can't do an AFR error calculation like I keep seeing in how-tos for MAF scaling.

[In-Tech]

Of course the tube can change some of the dynamics but not much with that 5 wire maf as long as the distance is similar. You can't hook that maf(or any other for that matter) straight to the throttle body and expect it to work, the pulses, angle of the blade, etc will screw any idea of that thing working correctly.

[Rocko350]

im not at a computer where I can open the tune files in the thread. OP did you leave the screen in the MAF? I may have missed that. I hope you did. You will need to rerun fuel trim adjustments to the MAF curve. Fats355 is dead nuts on. Your going to need to rerun your fuel trim learns on your MAF curve. As far as PE enrichment, I tuned an 8.1 in a g3500 drw bus of all things and found the enrichment ramp in rate was set stupid low. Its like a AFR adder. It slowly adds fuel to the desired PE AFR. But from the discussion id say you have a 2 fold issue right now. Too slow of enrichment rate and the maf curve is off. Disable PE and rerun your maf learns and then lets get back to PE.