PE enabled, but not activating (0411 8322)

[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]

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.

[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.

[woody80z28]

Made a huge datalog at varying RPM with the MAF disabled (attached). LTFTs are much closer with the MAF disabled. +/-2% for most of it...up to +5-8% at the top of the log. I adjusted the VE table and I'll log & retune another couple times.

Then I can work on the MAF. LTFT with the a history table for g/sec sound like a solid plan?

[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.