Stock LBZ MAF Size

[NickInMN]

I have a Hummer with an LBZ swapped in. I have an ECM with custom tunes but I wanted to try my hand at tuning so I bought an extra ECM and a FlashScan. I put a stock tune with VATS and EGR disabled on my second ECM. I'm getting the p0101 code. I don't see this code with my professionally tuned ECM so I suspect it is related to MAF scaling. The MAF is in a 4 inch tube. I've been searching all night and I can't find a definitive answer as to what size the MAF section is for a stock LBZ intake. Some posts say 3.5 inches, others say 4. What should my MAF table be for an LBZ with a 4 inch intake? Is there something else I should be looking at?

[bobo]

Maf at idle should be around 39g/s. There are some MAF sensor testing paramater tables in the DTC section. Tables C0901-0908. You can try to edit that and see if it clears the code. Here are some values to try:
Values are imperial not metric.


-4.1
211.9
500
3100
0.71
15.00
19.60
15.00
Stock



300.1
-50.0
6000
0
0.00
655.00
28.22
655.00
modded

[NickInMN]

Interesting, my table has different values. Since those are the test parameters it seems like changing those would mask the problem but not fix it. I'm going to do some logging and see what the g/sec is reading. Thanks!
24836

[killerbee]

In the interest of doing this right, definitely dont play with those values. Rescale your maf beginning with bobo recommended idle value. Scale the table so it reads 39-42 g-s, or 5-5.4 lb-min. Performance of your integration is fuel dependent and fuel is metered with your maf reading. You should be able to trim out the p0101 without defeating the code.

[killerbee]

Your maf is likely reading low with a 4" tube. (this is also typical with aftermarket intakes) You can verify with your maf log. I think 3.5" is the standard tube. Come up with a ratio of the cross sectional areas to use as an initial multiplication factor for expected maf readings. Multiply the whole MAF table by this factor.

[NickInMN]

I've had some time to play around with this and what I'm seeing is confusing. With my "tune" I'm seeing 59 g/sec at idle and I have the P0101 code along with P2565 code "Turbocharger Boost Control Position Sensor A Circuit High". Just for grins and chuckles I put my tuned ECM back in and I'm seeing the same thing, 59 g/sec at idle. The odd thing is neither of the two previous codes were present with the tuned ECM. Looking at the table bobo referenced, 59 g/sec should not trigger p0101. I scaled the MAF down to get 40 g/sec at idle, cleared the codes and they came back.

I hope my tuner didn't disable a bunch of codes but it seems weird that simply switching ECMs would give me those codes. I asked and he wasn't interested in telling me which kind of bothers me. I did perform a TC Relearn with my Tech 2 thinking maybe that would help but those two codes are still present.

It is a bummer I can't look at the DSP5 tune that's in there just to see what's turned off.

[killerbee]

Codes are disabled all the time by tuners. ALL THE TIME! There are more hack tuners than skilled tuners. The parameters you mentioned are just conditions that must be met before the P0101 diagnostic will run. When the diagnostic runs MAF is being compared to a boost and rpm algorithm. 59 at idle is clearly high at 680rpm and would definitely trigger the code.

[killerbee]

The P0101 disable technique is also the simplest way to deal with the plethora of poorly designed aftermarket intakes.

[NickInMN]

Interesting, this particular tuner is pretty well known for swapping a Duramax into Hummers. If what you're saying is true, and I have no reason not to believe it, he's turned off the P0101 code. The weird thing is the truck actually runs really well with his tune. If the airflow is off, how would that be possible?

[killerbee]

If the airflow is off, how would that be possible?

What are you asking?

[NickInMN]

What are you asking?

I should have been more clear. My understanding is airflow, determined by the MAF sensor, is used to calculate fueling. If the MAF reading at idle is 59 g/sec but the actual number is closer to 40 g/sec it seems like the ECM doesn't have the correct information. And if that's the case it seems like the engine should run poorly or at the very least smoke, which it does not since the computer thinks it is getting more air than it is and as a result provides more fuel.

[killerbee]

The fueling per maf schedule mostly becomes problematic for turbo spoolup, especially at high elevations. But that is when it is reading lower than normal, not higher. The LBZ at steady state will run on an air surplus, so you wont notice anything off. The induction system in general on the LBZ is ridiculously efficient. MAF reading becomes a problem more when it is low, it can cause the turbo to hang as the truck has a hard time increasing rpm.

[bobo]

Do some research on MAFless tuning. Your tuner most likely put in a good amount of effort to make an efficient tune without MAF metering. It can be done, but is a tedious process. Most “tuners” use the MAF to limit fueling. This is done on the factory calibration. I prefer MAFless tuning, but it’s not for everyone.

[NickInMN]

Do some research on MAFless tuning. Your tuner most likely put in a good amount of effort to make an efficient tune without MAF metering. It can be done, but is a tedious process. Most “tuners” use the MAF to limit fueling. This is done on the factory calibration. I prefer MAFless tuning, but it’s not for everyone.

I'll do some looking but that sounds like it is well above my pay grade!