Blow through maf tuning; car goes into safe mode

[camcojb]

Got the twin turbo up and running. I've tried un-plugging the maf to tune the VE but even though the trims are close it surges badly and dies. The main problem with the maf hooked up is if I roll into the throttle fairly hard (maybe 1/2 throttle tops) it backfires and almost dies; goes into safe mode and barely runs until you shut it off and re-start.

It never got lean at all, was high 11's a/f when that happened. Any ideas? Also any idea what else may have to be changed to be able to un-plug the maf and still have it run so it can be tuned?


Jody

[EC_Tune]

If the car/truck is `01 or newer, don't unplug the MAF as the air temp is in there too. That will definitely cause problems.

What is your g/cyl airflow? if you're over 2.3 g/cyl you will ALWAYS set a P1514 code and go into dead throttle mode. If so, watch your fuel pressure, if it dives on you, that can do it strangely enough. If not, you will have to scale the Injector Flow Rate down a percent and scale the VE table the same percent. Check it again. If you still go over 2.3 g/cyl, more downsizing is necessary.

EC

[camcojb]

If the car/truck is `01 or newer, don't unplug the MAF as the air temp is in there too. That will definitely cause problems.

What is your g/cyl airflow? if you're over 2.3 g/cyl you will ALWAYS set a P1514 code and go into dead throttle mode. If so, watch your fuel pressure, if it dives on you, that can do it strangely enough. If not, you will have to scale the Injector Flow Rate down a percent and scale the VE table the same percent. Check it again. If you still go over 2.3 g/cyl, more downsizing is necessary.

EC

I will apologize in advance. I am not new to tuning, but am brand new to this system.

This is an 05 GTO with a twin turbo 402 LS2. So if I exceed 2.3 grams/cylinder I have to scale the IFR and the VE table down if necessary to prevent this? I have an upgraded fuel pump and BAP so I'm guessing the fp is not the issue. Never got near wot and the AFR was in the high 11's, never leaned until the pop.

Thanks a lot for the help.

Jody

[EC_Tune]

BTW: I forgot to ask if you logged a code.
Even if you have P1514 turned off, it will *still* go off at ~2.3 g/cyl., you just won't see the code.

BTW: Turn up the P1514 table values all the way. The 1514 table is fine for NA cars but high boost apps it's a PITA & generally useless.

EC

[camcojb]

BTW: I forgot to ask if you logged a code.
Even if you have P1514 turned off, it will *still* go off at ~2.3 g/cyl., you just won't see the code.

BTW: Turn up the P1514 table values all the way. The 1514 table is fine for NA cars but high boost apps it's a PITA & generally useless.

EC

Sorry, what are the P1514 tables?

Jody

[EC_Tune]

They are the max airflow vs throttle position vs RPM. If you haven't adjusted these you will definitely need to crank them up to max.

Dang!

I just realized you are working on an 05-06 LS2. NO 1514 table!!

You do need to max out (8192 RPM) the P0068 RPM constant in Engine Diagnostics though so that test doesn't run. And the P0106 coolant (256 deg) too.
To get into VE mode set the MAF to fail at 0 hz. Don't go into boost though because there isn't a 2bar setup for the 05-06 LS2's.

EC

[camcojb]

They are the max airflow vs throttle position vs RPM. If you haven't adjusted these you will definitely need to crank them up to max.

Dang!

I just realized you are working on an 05-06 LS2. NO 1514 table!!

You do need to max out (8192 RPM) the P0068 RPM constant in Engine Diagnostics though so that test doesn't run. And the P0106 coolant (256 deg) too.
To get into VE mode set the MAF to fail at 0 hz. Don't go into boost though because there isn't a 2bar setup for the 05-06 LS2's.

EC

Thanks again. Feel better cause I couldn't find that one! I'll make the changes and do a lot of logging tomorrow.

Jody

[HSVZTT]

Camcojb,

did you resolve this - if so what was the issue. I think my tuner may be having the same issue with my 05' LS2

RGDS
Steve

[Bill@HPTuners]

also i believe their is a maf fix under OS you might want to upgrade to...its free btw.

[camcojb]

Camcojb,

did you resolve this - if so what was the issue. I think my tuner may be having the same issue with my 05' LS2

RGDS
Steve

Yes with more tuning and a swap back to the stock LS2 and twin turbos.

The 402 was supposed to be dead smooth idle, that was something I wanted. The turbo cam they spec'd idles at about 13" in Park at 900 rpms and 11-12" in gear. Not what I wanted so I pulled the motor and replaced it with the stock LS2. The turbo kit was made for that anyway and the 402 motor will be going in my 67 Chevelle.

As far as the cure I shut off thoses tests like they said and started tuning more and it never happened again.

Jody

[camcojb]

also i believe their is a maf fix under OS you might want to upgrade to...its free btw.

Where would this be found? Not sure what OS is.

Jody

[Bill@HPTuners]

editor-upper left hand corner where it says OS click on it and you should see a tab to apply the maf fix.

[camcojb]

editor-upper left hand corner where it says OS click on it and you should see a tab to apply the maf fix.

OK, thanks. I was looking on the forum and website for a download! Now it showed an unpatched 11500 frequency and a patched 15000, so I swapped to the patched 15000. Does this extend my maf range for boost? Does it change any of the low maf frequency tables I've already done?

Thanks!

[Bill@HPTuners]

all i know is gm set up the computer to basically "turn over" back to 0 when you hit the maf frequency meaning you'd go lean when you ran out of maf room.

[HSVZTT]

Thanks Foff. FYI - I showed my tuner the post (prior to your reply) thinking it may help. Here in Australia that was yesterday morning. I had not had the chance to give him your reply though, when he rang me last night @ 9pm saying all fixed and the thing is making 450rwkw without trying (not fully tuned yet)!!!
Whilst explaining the techno jargon to me on how he found the fault, he mentioned the aconym OS (which i don't know what that is) that was part of the problem and it all clicked. Not 100% sure what he had to do but 10 out of 10 for you though foff , with out any 'real' info from me, you picked the general area of the fault.
BTW - the car is an Australian '05 LS2 Commodore (same as the Monaro in the U.S)

[Chris@HPTuners]

make sure you use the "Write Entire" function to apply the patch (you only need to do this once).

Later OS's do not require this patch as GM has finally fixed the bug (the fix will not show in the editor).

Chris...

[EC_Tune]

WOW GM Fixed their screwup?!! Amazing...