PE enabled, but not activating (0411 8322)

[Fast355]

Hmmmmmm... I just tested out the BIN, and with the PE EQ ratio set for 1.18, the wideband was reading just over 16:1! That's supposed to be about 12.5:1. Stock was 1.240, so there's no way it could be backwards right? Cause 1.18 lambda is about 16:1...

But the good news is, it does appear to be entering PE. Wideband was about 14.7ish at moderate throttle, then moved to 16:1 at WOT.

Sounds like low fuel pressure, unmetered air leak or a dirty MAF to me or some poor WOT tuning masked by closed loop at WOT.

[woody80z28]

Maybe the factory tuning its really bad? Truck is stock, with a drop in filter and smooth intake tube. I've read something about a MAF reading incorrectly if the tube isn't the same diameter. Maybe corrugated vs smooth also makes a difference?

[LRT]

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[woody80z28]

Interesting nugget about PE on an 8.1... I've been making comparison pulls up a mountainside headed out of town as a "dyno" but they are only taking about 20sec to go from 2000-5000 in 4th gear at WOT. I can't think of any place steeper to try and prolong that. Maybe I could try 5th.

I just flashed a PCM set to fail the MAF instantly and run on SD. I want to get that in today and try it if it stops snowing.

If it really is open loop activating and not PE, I recall a table for open loop EQ that can probably be purposed to work like PE.

I'd like to try your bin as well. Can you give a hint of what's done to it? Just in case it's "not defined" in the xdf.

Thanks

[LRT]

....

[woody80z28]

Gotcha. Thanks. Looks like I was editing my post when you added yours. That's the exact kind of thing I was envisioning to get around a PE issue.

[woody80z28]

Great success!

I modified the LRT bin to also disable the MAF and mistakenly flashed the non-modified one. AFR was low 14s. So I looked at it and realized what happened, flashed a MAFless copy and AFRs were in the low 12s. My ~19-20sec "dyno" pull only took 16sec! That's a definite improvement.

So I know I need to do some MAF scaling. Very excited though...cause now I know I can make changes and see results.

Thanks to everyone who helped out. I would not have figured this out on my own.

[In-Tech]

Sounds like low fuel pressure, unmetered air leak or a dirty MAF to me or some poor WOT tuning masked by closed loop at WOT.

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

[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.

[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.