MAF Locked out or Not? VE Tuning Twin Turbo 8.1

[JonathanLeskewich]

Hi guys,

My workhorse motorhome disables the throttle if the P103 MIL goes on... I have been trying to tune the VE table for days and my fuel is all over the place. I have disabled the MAF (Fail freq. high), but I have disabled the MIL so that the motorhome doesn't go into limp. I tried to check if the MAF was disabled by zeroing out the MAF freq. table. When I do this the vehicle will not run. Starts and stalls, that's it. Put the values back in and bam, it runs again. This makes me think the MAF is not truly disabled.

Vehicle has upgraded injectors (60 lb) a Walbro fuel pump and twin turbo's with a intercooler up front. Running 92 Octane.

Please don't laugh at the log, it's embarrassing. I had it tuned really good on the MAF, but I need 2 bar for higher boost and the MAF cuts short.

Here is the tune and the log. Some advice would be appreciated, thanks in advance.

Jonathan2 Bar VE 18.hpt2 bar map ve 18.hpl

[blindsquirrel]

If it doesn't have a current DTC for P0102 or P0103 it will not be in speed density, and trying to adjust the VE when it's not in SD will not work out well.

What steps - exactly - are you using to disable the MAF when the throttle stops working? Exactly which settings do you change? Because I do not think MAF Fail High=1Hz and Dynamic High RPM Disable=12,000 is the way it's supposed to be.

Do you have a 3-wire or 5-wire MAF? If 3-wire and no integral IAT to worry about, simplest way to force it temporarily would be to just unplug the damn thing.

Are you tuning with a wideband or by fuel trims? If wideband tuning, why are trims active (and showing +30% nearly across the board, yikes)?

[JonathanLeskewich]

I?m tuning with a Wideband yes. Unfortunately it is a 5 wire MAF. I used frequency and dynamic rpm high 12,000 to disable it.

It does throw the check engine Light if I let it (leave the DTC active). I guess my question is whether the MAF is still disabled if the light isn?t on?

LTFTS are disabled by engine temp 283. I don?t think it?s using them but I don?t have enough experience to say it is for sure or not.

What would be another way to disable the MAF or do this? I followed the goat rope garage video on YouTube exactly for the gen 3. Maybe it doesn?t work? Everything else has worked from that guy.

Jonathan

If it doesn't have a current DTC for P0102 or P0103 it will not be in speed density, and trying to adjust the VE when it's not in SD will not work out well.

What steps - exactly - are you using to disable the MAF when the throttle stops working? Exactly which settings do you change? Because I do not think MAF Fail High=1Hz and Dynamic High RPM Disable=12,000 is the way it's supposed to be.

Do you have a 3-wire or 5-wire MAF? If 3-wire and no integral IAT to worry about, simplest way to force it temporarily would be to just unplug the damn thing.

Are you tuning with a wideband or by fuel trims? If wideband tuning, why are trims active (and showing +30% nearly across the board, yikes)?

[blindsquirrel]

Yes, sorry, I was backwards on the Dynamic disable. Setting it way up high is correct.

But, you cannot have the MAF DTCs set to No Error. The box checked for MIL or not has no affect on whether the test runs or not, but the drop-down box must be MIL on First Error for the test to run and the code to set and SD to take over. The one you have set to MIL on second means it won't go to SD on the first engine run cycle, it'll wait until you turn the engine off and restart. Not the way you need it to be. You need it to fail the MAF as soon as possible every time the engine starts and runs.

Does it set any other codes when the throttle stops working? Does the throttle quit working with the MAF unplugged? I would like to see a log (and the tune file used) of it with the MAF fail set correctly, and the throttle not working.

You have fuel trims active in that log. That means your wideband data is including what the trims are adding and you are not getting accurate data. Closed loop is disabled however there are points in that log where LTFT goes to +11% or so, not sure how that's possible but it must be fixed. There is another separate drop-down box at Fuel > Open Loop you have missed, STFT Open Loop is still set to Enabled ("If enabled, use STFTs during open loop operation"). At the one spot in the log where it showed some boost it was commanding 10.5 to net 11.6 on the wideband, because the trims are still active.

screenshot.12-06-2021 09.33.07.png

I also have to ask... why in the world are you even trying to keep the MAF on a setup like this? Overly complicated plumbing for twin turbos, restrictive, and it would probably run better in pure SD mode after all is said and done anyway.

[JonathanLeskewich]

Ok I changed the STFTs to disabled, thanks for that!! The video I watched did not mention it. I actually am trying to get rid of the MAF because you are right I did get it quite tuned, but the fuel still fuel still jumps around and is only stable-ish with the MAF.

I will get out there and try and do a log today with the DTC's (101, 102, and 103) set to fail on first. I wish I could just follow the standard GM gen 3 advice to make this work, but it seems like mine is just different enough to make it difficult. It's a workhorse chassis with an Allison 2000...it has a lot of separate non GM controllers that communicate on J1708. There is very little info on those things out there.

Thanks for the help. I'm hoping to slowly get there with patience!

Jonathan

Yes, sorry, I was backwards on the Dynamic disable. Setting it way up high is correct.

But, you cannot have the MAF DTCs set to No Error. The box checked for MIL or not has no affect on whether the test runs or not, but the drop-down box must be MIL on First Error for the test to run and the code to set and SD to take over. The one you have set to MIL on second means it won't go to SD on the first engine run cycle, it'll wait until you turn the engine off and restart. Not the way you need it to be. You need it to fail the MAF as soon as possible every time the engine starts and runs.

Does it set any other codes when the throttle stops working? Does the throttle quit working with the MAF unplugged? I would like to see a log (and the tune file used) of it with the MAF fail set correctly, and the throttle not working.

You have fuel trims active in that log. That means your wideband data is including what the trims are adding and you are not getting accurate data. Closed loop is disabled however there are points in that log where LTFT goes to +11% or so, not sure how that's possible but it must be fixed. There is another separate drop-down box at Fuel > Open Loop you have missed, STFT Open Loop is still set to Enabled ("If enabled, use STFTs during open loop operation"). At the one spot in the log where it showed some boost it was commanding 10.5 to net 11.6 on the wideband, because the trims are still active.

screenshot.12-06-2021 09.33.07.png

I also have to ask... why in the world are you even trying to keep the MAF on a setup like this? Overly complicated plumbing for twin turbos, restrictive, and it would probably run better in pure SD mode after all is said and done anyway.

[JonathanLeskewich]

Actually I found a log file where it goes into limp. I don't know what to look for? You can see that the throttle isn't really working. How do I see what it is commanding?

2 bar map ve 12 BE and PE.hpl

Ok I changed the STFTs to disabled, thanks for that!! The video I watched did not mention it. I actually am trying to get rid of the MAF because you are right I did get it quite tuned, but the fuel still fuel still jumps around and is only stable-ish with the MAF.

I will get out there and try and do a log today with the DTC's (101, 102, and 103) set to fail on first. I wish I could just follow the standard GM gen 3 advice to make this work, but it seems like mine is just different enough to make it difficult. It's a workhorse chassis with an Allison 2000...it has a lot of separate non GM controllers that communicate on J1708. There is very little info on those things out there.

Thanks for the help. I'm hoping to slowly get there with patience!

Jonathan

[kevin87turbot]

Load this revised file and give us a datalog when you can. It will fail the MAF properly.

2 Bar VE 18 kw mod.hpt

[blindsquirrel]

What part number MAP sensor are you using, and have you verified it actually uses specs of 200/10.33? (those numbers are defaults auto-filled when the 2bar OS is applied)

[JonathanLeskewich]

I disabled the MAF now successfully thanks! The throttle was getting messed up from the 068 code logging (differential between MAF and VE too great). I adjusted that table in the DTC section and it worked.

I will have to try your file adjustments tomorrow, wife is back with my 4 kids! Thanks for the hint about the MAF values too I will check that.

Here is my last log with MAF failed and DTC's on, with LTFT and STFT disabled. I think I am finally on my way now.

Log 28.hpl

[JonathanLeskewich]

Actually I just checked my stock MAF file has the 94.43 and 10.33. Do I need to change it back then? Or is it scaled by the new 2 bar OS?

[blindsquirrel]

If you still have the stock sensor then you need to use stock settings. If you have something else, you need whatever is correct for whatever it is.

edit: To be ultra-super-clear: This is the MAP sensor, not MAF.

[JonathanLeskewich]

Ok, that almost did confuse me. The Map is a GM 2 bar. I replaced the 1 bar.

Thanks again for all the help!!

[blindsquirrel]

Buuuut... what I mean is, 200/10.33 is not meant to be correct for anything, it's simply placeholder values that get changed when the OS is applied. If you have looked up your specific MAP sensor, and it really truly does use settings of 200/10.33, then OK. But if not, do not assume it's right simply because you have "a 2 bar sensor".

[JonathanLeskewich]

Ok got you thanks. I just have to search on the internet then??

QUOTE=blindsquirrel;653368]Buuuut... what I mean is, 200/10.33 is not meant to be correct for anything, it's simply placeholder values that get changed when the OS is applied. If you have looked up your specific MAP sensor, and it really truly does use settings of 200/10.33, then OK. But if not, do not assume it's right simply because you have "a 2 bar sensor".[/QUOTE]

[blindsquirrel]

If that's your preferred method for finding out the correct linear & offset settings for your particular MAP sensor, then yeah.