Unplugged my MAF.... running ok but rich WOT

[S8ER01Z]

Can anyone clear this up for me? I noticed during logging that I was only seeing .71 g/cyl around 5100rpm (which is where I stopped making power on the dyno) then it falls off and after reviewing logs from other cars this seemed low. I decided to unplug my MAF in case something is wrong with it. I'm running a "tune" which is pretty much a stock 2001 M6 tune with raised limiter settings. After unplugging the MAF I drove to work this morning and noticed at WOT my AFR was in the 11s.... previously I was sitting in the 12s with the same tune using the MAF. Any thoughts? Did I miss something important? I thought simply unplugging the MAF would be enough to rule it out as the problem but clearly I was mistaken.




2001 Camaro Z28 Base (Saiter 2014 Modified).hpt
TuneDiff.jpg
default imperial and PLX DM6 and histos MAF in HZ.cfg

Using the MAF
stocktune1.hpl

MAF unplugged (not much WOT data as I decided it wasn't a great idea to do a long pull)
nomaf.hpl

[blownbluez06]

You can't unplug the MAF and leave it in the tune or the table in the scanner and not screw up things. It is part of the calculation for fuel until you make it not a part for fuel calculation and when you do, it must be done properly. If the MAF is failed in the tune, take it out of your table. Referencing it in the scanner (at least in some cases I've seen, not sure of all cases), it pulls the MAF back into the loop. If you wish to know if it's screwing things up, Make sure the MAF is properly failed by looking for the MAF DTC's and then log the car with the MAF in the table, looking at the cylinder air and dynamic air measurements. Then remove the MAF from the table and see if the values go way up.

[S8ER01Z]

I verified on the wide band gauge in car that the numbers were in the 11s. Are you saying the PCM didn't fail out correctly and was still trying to use the MAF or that the scanner information could be bogus because it's trying to use the MAF data?

I will fail it out per the MAF tuning guide info (set "MAF Fail High" to 0), check the data then pull the MAF references out and see what happens. Thank you for the help!

[93camaro_zzz]

Yeah, I know as a fail safe I always fail the MAF, but then do not change the DTC codes yet, to see if they pop up. Then I KNOW it is failed. I have learned all of this from experience. lol Then I go back, and change the DTC codes. It is quite a bit more work, because you have to sit in the hot sun while you flash in a tune 2 separate times, but it definitely saves some headaches a lot of times.

[blownbluez06]

I verified on the wide band gauge in car that the numbers were in the 11s. Are you saying the PCM didn't fail out correctly and was still trying to use the MAF or that the scanner information could be bogus because it's trying to use the MAF data?

I will fail it out per the MAF tuning guide info (set "MAF Fail High" to 0), check the data then pull the MAF references out and see what happens. Thank you for the help!

It's been a long time since I dealt with this specific circumstance, but if I recall, having the MAF zero'd out yet having the MAF in the table creates a conflict. you're telling the PCM to not look at it and by having it in the scanner, you're creating an argument, telling it to look at it. When the MAF show's zero and it's averaged into the PCM's airflow calc, it's cutting airflow down and referencing fueling and spark from that skewed airflow value. If you saved the log, remove the MAF from your table, scan the car again and compare airflow values as well as your spark table histograms. You should see everything operating in different places.

[blownbluez06]

Yeah, I know as a fail safe I always fail the MAF, but then do not change the DTC codes yet, to see if they pop up. Then I KNOW it is failed. I have learned all of this from experience. lol Then I go back, and change the DTC codes. It is quite a bit more work, because you have to sit in the hot sun while you flash in a tune 2 separate times, but it definitely saves some headaches a lot of times.

I don't follow what you're saying. All you have to do is fail the MAF one time with the DTC codes changed and it will still report the DTC. the only DTC that won't report is "no error reported" and if you're using "no error reported" that's a real bad idea.

[93camaro_zzz]

Yeah, what I mean, is whatever method you use to fail the MAF, whether it be unplugging, or setting the fail frequency, I do that, and wait for the codes to pop. I know in theory it should be that you do exactly what you say blownbluez06, but ever since one time when I unplugged the MAF on a car and it did not fail, and I was driving around trying to tune the VE of an unfailed MAF car, I adopted my current method. I dunno, to each his own.

[S8ER01Z]

Ok, update...MAF is failed now for sure (MIL, no data, removed from config on my interface)...without even hooking up my HPTuners to log my wide band is reporting mid 11s at WOT.... FML... I have no idea what is wrong now.

[madmann26]

Ok, update...MAF is failed now for sure (MIL, no data, removed from config on my interface)...without even hooking up my HPTuners to log my wide band is reporting mid 11s at WOT.... FML... I have no idea what is wrong now.

So this is at happening at WOT, right?

The answer lies in your EQ ratio that you are commanding in PE mode. I looked at your tune and you're commanding 11.7-11.5 AFR at WOT. If you want to command, let's say 12.5 AFR, use 1.17 as the EQ ratio.

[S8ER01Z]

Stioch/current ratio @ rpm... got it. Thank you for the help...its seems obvious now. I guess with the MAF the AFR ends up near 12.5 because its compensating somehow.

I had hoped the stock tune would be closer but I've obviously made enough changes its going to require some work. I will report back and I make some changes. Thanks again!

[madmann26]

Stioch/current ratio @ rpm... got it. Thank you for the help...its seems obvious now. I guess with the MAF the AFR ends up near 12.5 because its compensating somehow.

I had hoped the stock tune would be closer but I've obviously made enough changes its going to require some work. I will report back and I make some changes. Thanks again!

You can get the EQ ratio yourself by using the formula: 14.68/xx.x (wanted AFR)= EQ ratio.

[S8ER01Z]

Thank you guys for the help with this... Spent the past week logging and modifying the VE Main table. Hopefully all this effort pays off.