Getting closer on a Gen III swap - VE Tuning /MAF disable

Got a new fuel tank, lesson learned don't let project cars sit for years with 2 gallons of gas. Probably could've been fixable with some acid washes and rinses but time is more hard to come by than money, not that I've got stupid money but I sure as hell don't have much time with two kids and running a business.

I think I'm doing this correctly. Scaled my VE table up based on some previous stuff and I think the tune is looking pretty good. STFT are just about all single digits. I just would like for someone to verify I'm in VE and not using the MAF. It looks like the MAF is still being read in on the log, but it does show on the log details the following:
Trouble Codes:
P0103 - Mass or Volume Air Flow A Circuit High (Pending, Current)
Controller Type ID By OS: 512

I know Goat Rope doesn't have the best rep around but I followed his guide on disabling the MAF so if I need to do something different just point me at it.

Only issue I'm having is when coasting to a stop sometimes it wants to stall. I know the cause is probably due to no VSS but the Holley Crossmember with the Dakota Digital VSS Cable pass through are just not playing nice and the tension was causing a bad leak.

Car:
Specs:
LQ4, Stage 3 truck cam, headers, dual 2.5 exhaust in a GM A-Body. 42lb FIC injectors, actually flow 50ish at 58lbs, truck rails and return style regulator. 700r4 transmission, so no tcu components. Stock heads and pistons/compression.

Previous Threads:
https://forum.hptuners.com/showthrea...n-a-cammed-lq4
https://forum.hptuners.com/showthrea...a-cam-swap-lq4

Attachment 157267
Attachment 157268

MAF is still failed - MAF Fail High = 0 Hz, & Dynamic High RPM Disable = 10,000 RPM.

Oh, and don't log the channels for MAF Hz & Mass Air Flow when you've intentionally failed the MAF. That's asking the PCM to give you data on a sensor you're telling it not to look at, some of them get confused when you do that.

Great so the MAF was off and the STFT adjustments were not using MAF data. I'll turn those logs off.

I'll do some more logs and try to fill more boxes out on the STFT and make adjustments. Then figure out the MAF tuning side of things and put some miles on this heap of shit finally. Not sure if I'm going to bother throwing more timing at it right now.

Fuel trims have nothing to do with whether it's in SD or MAF or blended... as long as it's in closed loop, trims are trims, only difference is which table you apply the corrections to. Closed loop works the same whether it's MAF only or SD or stock blended, failing the MAF for speed density does not equal open loop.

Fail the MAF (like you have it now) to collect data to apply to the VE table. Then un-fail the MAF and set the Dynamic really low (like 100 or 150) to collect data to apply to the MAF table.

I guess I'm going to call the VE portion of this little project complete. Drove a little 1.5 mile circuit of roads about 6 times. Kept the 700r in manual mode to keep RPMs up. I did it a little different than how some videos I've seen recommending. Rather than just pasting or pasting by half I took time to eyeball the ranges and increased things in a more linear fashion. If for example on a segment of a row the numbers were going 2 4 3 5 4 7 7 4 5 3, I might increase the percentages as 2 3 4 5 6 7 7 6 5 3 when doing the adjustment. It was slow but felt better logically to me.

By the last run I'd say 97-99% were low single digits. I had just a couple individual outliers that were like 10-12% red but the numbers on the VE looked fairly linear to either side and the STFT value on either side would be very low like 1-2% so I'm just gonna call them anomalies and see if they show in the LTFT after they are back on and the car is driven more.

I'm pretty happy with how it is behaving. There was a loud noise with the IAC before so I cut a few g/s from the idle table and now it's like a factory LS starting up. Also upped the idle by 150rpm across the board which took me from a 750 idle to 900 when warm. 750 sounded better but at 900 the stall on coasting stops is gone.

Onto playing with the MAF and wrapping this up.

Thanks everyone. knock on wood this will be my last post here for quite a while. When I'm done I'll post the final just in case it gives some other new a starting point for a mild cam 6 liter some day.

Quote:

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Originally Posted by 72cutlass

I guess I'm going to call the VE portion of this little project complete.

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1.5 miles is not long enough of a drive.
nothing is stabilized, and the ecu is probably doing behind the scene tests that are messing with fuel

but, post your data log so we can see it. You think its 'complete' why not let 40 more pairs of eyes look at it and give you feedback..

when i datalog i have a 7 mile route going out, and coming back just for reference

Quote:

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Originally Posted by bk2life

1.5 miles is not long enough of a drive.
nothing is stabilized, and the ecu is probably doing behind the scene tests that are messing with fuel

but, post your data log so we can see it. You think its 'complete' why not let 40 more pairs of eyes look at it and give you feedback..

when i datalog i have a 7 mile route going out, and coming back just for reference

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Cool, thanks for that. I'll take it for some longer ones and post the log this weekend.

I did actually map out the little route I was doing just now and it was 4.12 miles.

All logging was being done after it was up to temp.

I'd upload one of those but I unfortunately wasn't saving the logs, just the tune revisions.

The logs auto save every time you stop it. They are in one of your documents folders, such as follow the path in the search bar in this screen shot.

Attachment 157443

Good to know on the autosave thing. I've attached a log from this afternoon and the latest tune I'm running around with. Car feels like a dog, but not sure what I was expecting from a low compression truck motor and a small cam. Maybe it's a dog, or the transmission is slipping or maybe owning a bolt-ons gen 2 viper and previously running a big block in this car last time it was on the road probably screws my sense of speed. Nothing some boost can't fix.

In any case it seems like it is running good enough to not blow itself up which is all I'm really after. It gets rich at 1200 but the map is already so ugly looking I feel like jacking up those points by 12 points will get it even more jagged.

Attachment 158023Attachment 158024


Edited to add a much longer run from later this evening.
Attachment 158025

And another one. The ride to the kid's karate it seemed to got hot. No issues on the ride home. Maybe there was an air pocket or something working itself out. Similar ambient.

Looks like you are getting close, didn't see any issues with temperature, i would try re-enabling closed loop fueling/LTFT, plot LTFT + STFT against your VE with VCM scanner, then apply to VE table as you have been doing, smooth table and reset LTFTs between changes

Something is happening at about 1min - 1min 30sec, and about 2min - 3min, O2s both no longer switch, appears this is when you are idling

Quote:

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Originally Posted by twenglish1

Something is happening at about 1min - 1min 30sec, and about 2min - 3min, O2s both no longer switch, appears this is when you are idling

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I think I see where you are talking about. Its when the kPA vs RPM is 50/0.8. It is sitting as a big fat and rich cell right there on every log every time.

latest tune is attached on this post, I forgot I tweaked it again on those last to logs. So this is what is being run in the car on the two 2025-03-5b & 2025-03c logs.
Attachment 158032

I just enabled closed loop for the LTFT. So I'll do some driving the next few days and see what those do.

Always brings up the questions about the fuel system too, so you are running a 58psi vacuum referenced regulator? And verified 58psi with vacuum hose disconnected from regulator? Are these the injectors you are using? Has it been verified that the fuel injector data was entered correctly?

https://fuelinjectorconnection.com/p...lb-ls2-l92-lq4

I haven't looked at the logs yet, I have looked at the VE table and it's a mess right now. It's unrealistic to have this engine be more than 80% efficient at 50 kpa and 800 rpm. Something is wrong, something like fuel system description, or air leaks, something...

Quote:

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Originally Posted by abc

I haven't looked at the logs yet, I have looked at the VE table and it's a mess right now. It's unrealistic to have this engine be more than 80% efficient at 50 kpa and 800 rpm. Something is wrong, something like fuel system description, or air leaks, something...

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Yeah, I have something going on unfortunately. I have not been happy with the look of the VE table but the logs were okay so I thought I was good. Last night I pulled out separate b1 and sb2 voltages. Bank 1 is running significantly different than Bank 2.

Guess I'll figure that out this weekend.

Post the datasheet that you used for the fuel injector parameters, verify fuel pressure, at rail, engine running, regulator vac line disconnected, make sure there are no air leaks regarding intake or exhaust, particularly near the O2s if there are joints, but it is critical that there are no exhaust leaks before the O2s, to a couple feet after, ideally no leaks anywhere. Exhaust pulses will draw in air and skew readings. Also check intake for any possible forgotten open vacuum ports. Finally is this a drive by wire or cable throttle body? Tune file has it as a drive by cable, and you are logging IAC position so id assume drive by cable, but need to confirm.

Quote:

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Originally Posted by twenglish1

Post the datasheet that you used for the fuel injector parameters, verify fuel pressure, at rail, engine running, regulator vac line disconnected, make sure there are no air leaks regarding intake or exhaust, particularly near the O2s if there are joints, but it is critical that there are no exhaust leaks before the O2s, to a couple feet after, ideally no leaks anywhere. Exhaust pulses will draw in air and skew readings. Also check intake for any possible forgotten open vacuum ports. Finally is this a drive by wire or cable throttle body? Tune file has it as a drive by cable, and you are logging IAC position so id assume drive by cable, but need to confirm.

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DBC, injector info spreadsheet posted in the first post here
https://forum.hptuners.com/showthrea...a-cam-swap-lq4

I'm leaning towards the exhaust leak(s) being the issue. I will get it sealed up tight over the weekend.

Injector data appears correct, and i am pretty sure the express vans were all DBC so there should be no issue with the PCM driving the IAC, TPS voltage at idle seems like it is a little high? Need to add throttle position percentage to log and make sure that it reads zero with throttle closed at idle, this will cause issues if it is not 0 at idle.

Quote:

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Originally Posted by twenglish1

Injector data appears correct, and i am pretty sure the express vans were all DBC so there should be no issue with the PCM driving the IAC, TPS voltage at idle seems like it is a little high? Need to add throttle position percentage to log and make sure that it reads zero with throttle closed at idle, this will cause issues if it is not 0 at idle.

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I'll add throttle position percentage to it. Hopefully have some time to get the exhaust sorted and do some driving this weekend.