Ductape

Wow, 9 responses in 2 hours! Thanks guys and especially Foff for the link.

Mike

02sierraz71_5.3

iTrader: (2)

You have to disable the code completely so that nothing is reported, on the status bit not sure never had to use it.

foff667

iTrader: (1)

if no error is reported wouldnt that leave the maf functional?

02sierraz71_5.3

iTrader: (2)

Not sure thats where the status bit would come in, I havent messed with it much to be honest. I wont tune an FI setup without a map that can read boost and proper OS.

dewmanshu

iTrader: (4)

yeah...02sierraz71_5.3...2 questions here (we are sorta on topic w/Duct tape's question being answered already)

1) fine tuning the maf y setting the high rpm rate low would be great. That seems answered.

2) second is, for a part maf/ve settings. 1bar, no need to screw with it. 2bar though, I want to set the fail rate lower like say 8000hrtz. But if I turn that code off, it will never fail. So, code to report-check. pass 8000hrtz and code sets and pcm goes full SD-check. Now when maf reads below 8000hrtz again (code still set) will it instantly revert back to maf/ve "normal" settings/readings? thus letting me run a limited maf tune.

I guess it will really, cuz plenty of people have "maxed" their maf's and once they let off the throttle it goes back to maf. right?

dc_justin

iTrader: (13)

I think you meant to say with a map that can read positive pressure. If it can't, it's 1 bar, and it would be nuts to fail the MAF on a boosted 1 bar MAP setup.

02sierraz71_5.3

iTrader: (2)

thanks for ketching that

12secSS

iTrader: (30)

Once the MAF has failed, the PCM will not reactive it when you go back under that value, at least not until you restart the vehicle and it goes through the test to determine if something is failing again or not. Since at start up the MAF Fail of 8000hz has not been exceeded, it will activate the MAF until it exceeds that value. By setting the MAF Fail to 8000hz, the PCM will switch to SD mode until the car is restarted. So after every WOT run, turn off your truck and restart it to drive in MAF mode again. That is what that fail mode does.

I will have to check again, but I believe there is a setting for enabling/disabling steady state MAF fueling. Bill (foff667) may have to look into this, as I am away from my tuning software at the moment.

As to the original question:
The VE is used during mild to agressive throttle transitions, where the MAF would be too slow to respond on low speed airflow areas (like putting around town going from stop light to stop light). Hence why it is crucial to tune the VE first as it is the foundation for unstable throttle fueling, which if untuned can lead to lean transition until the MAF kicks in, resulting in knock retard when you initially get on it. The MAF controls all steady state (cruising on the freeway at 60mph) and WOT above 4000 rpms.

02sierraz71_5.3

iTrader: (2)

Ill admit I havent messed with it much its an idea I had but I havent played with it. Foff has a point with not reporting the error and it not failing over to be honest Ive never tried it and bit logged so I can tell if it actually is failing over even though the DTC isnt reported. I was under the impression that even though the DTC isnt reported it could still fail over but I could be wrong.

dewmanshu

iTrader: (4)

ARGHGHGHH!!! Then how the hell are some people "supposedly" running these 2bar/maf combo tunes where this is exactly what is happening..."supposedly".

I played with a truck and it "seemed" to work for me, failing and returning. SInce I didn't know of a bit staus to use, I just made the MAF like +35% rich after my fail hrtz. Then I tuned it in SD making everything before 8000hrtz some what lean, around 3 to 5% lean. Then re-enabled the maf and tuned it so the tune was fairly spot on. Then I ran it hard. It would not go super rich (obviously due to fail rate) but it stayed spot on during normal driving. Leaving me to believe it was following the maf which i tuned fairly spot on earlier versus SD which was fairly lean. And also left believing the failing of the MAF was only temperarly. Worked well for a day. Next day it went back to as you are describing(which quiet frankly is what I always expected it to do, but "supposedly" others have it working.