Failed MAF = Intermittent Stumble

[Cringer]

The proposal would be to go from this equation:
VVE Airmass = (ConstCoeff) + (MAPCoeff * MAP) + (MAP2Coeff * MAP^2) + (RPMCoeff * RPM) + (RPM2Coeff * RPM^2) + (MAP.RPMCoeff * MAP * RPM)

To this equation:
VVE Airmass = (ConstCoeff) + (MAPCoeff * MAP) + (RPMCoeff * RPM) + (RPM2Coeff * RPM^2) + (MAP.RPMCoeff * MAP * RPM)

Basically go from 6 to 5 coefficients. My concern is that now you are going to shape the VVE table with less resolution and the other 5 may not be able to pick up the slack effectively. The good news is that with VVE Asst. 1.5 I can define whatever equation I want, so I can force it to shape with 5 rather than 6 coefficients. I will see what I can see.

OK I was able to implement "Verlon Mode" pretty quickly!
verlon mode.png

Here is the starting shape defined with the full 6 coefficients
VVE New.jpg
Here is the attempt to mirror that same shape with only 5 coefficients
VVE New.jpg
They look identical! I put the new and old VVE literal values in a spreadsheet and compared the values, the min percent difference is -.52% and the max difference is .30%! That is a total error of .82%...less than a percent! I was not expecting that at all. The downside of using my tool in Verlon mode would be that you would have to copy all 5 coefficients by hand because if you pasted the VVE values and calc'd coeff, HPT would break it down into 6 coefficients.

Unfortunately with my new found transmission issues, I won't be able to test for a while. So if anyone wants to test a 5 coefficient Verlon work around mode hit me up with your numbers and I will generate them.

[GHuggins]

OK I was able to implement "Verlon Mode" pretty quickly!
verlon mode.png

Here is the starting shape defined with the full 6 coefficients
VVE New.jpg
Here is the attempt to mirror that same shape with only 5 coefficients
VVE New.jpg
They look identical! I put the new and old VVE literal values in a spreadsheet and compared the values, the min percent difference is -.52% and the max difference is .30%! That is a total error of .82%...less than a percent! I was not expecting that at all. The downside of using my tool in Verlon mode would be that you would have to copy all 5 coefficients by hand because if you pasted the VVE values and calc'd coeff, HPT would break it down into 6 coefficients.

Unfortunately with my new found transmission issues, I won't be able to test for a while. So if anyone wants to test a 5 coefficient Verlon work around mode hit me up with your numbers and I will generate them.

Damn, that was quick. SO you just need to hand paste the coefficients into the editor? That's it??? Doesn't seem that bad at all.

We probably do need one thing clarified before moving forward. Since the coding is using some of these tables individually or at least one of them, are any of the others used that way so doing it with 5 tables vs the 6 won't throw anything else off? I've often wondered if individual tables were being used by other tables, especially in the torque model coefficients as spark and airmass seem to control things more so than the rest. Anyway..... Great work people. Also take it cycling the tcc didn't free the valve up?

[verlon]

Wow nice work! We all applaud your work in this!

Thanks.

Did you do all this analysis in assembler or is there an option to view in a higher level language?

In assembler.

OK I was able to implement "Verlon Mode" pretty quickly!
verlon mode.png

[Cringer]

Also take it cycling the tcc didn't free the valve up?

I haven't raised the tires yet and manually locked/unlocked the TCC. I really feel like before I start the engine up again I need to check for glitter/clutch in the ATF and see how cooked it is.

[GHuggins]

I haven't raised the tires yet and manually locked/unlocked the TCC. I really feel like before I start the engine up again I need to check for glitter/clutch in the ATF and see how cooked it is.

You might want to just go ahead and drop the valve body at that point as long as there's not too much in the pan clutch wise. It only takes the smallest piece of anything to make a valve stick. With yours being partially stuck on I'm leaning that way.

[Alvin]

I run into this VVE bug almost daily with the stuff I do. I could test running map^2 = 0 i either get my VVE editor redone or you want me to try cringers.

[Cringer]

I run into this VVE bug almost daily with the stuff I do. I could test running map^2 = 0 i either get my VVE editor redone or you want me to try cringers.

If you email me the HPT file with the final VVE shape you want, I will convert it over.
dankunkel at gmail dot com

[LS ROB]

First, please leave "Verlon Mode" as a thing. I love that haha!! Secondly, great work gentlemen! And lastly, I will excuse myself and let the men continue to discuss such matters.

[InfraRedline]

I know this is a few months old, but I don't come on here too often and there is a wealth of discovery in this thread. I work on mostly imports so don't use HPT too terribly much anymore, but personally own a 2009 C6 ZR1 and have noticed a good bit of the behavior mentioned in this thread. My ZR1 is tuned on speed density with a failed MAF and the dynamic enable/disable set high. Ever since going SD I would notice after a pull I would get one or two quick stumbles once I slowed down to cruising speed, usually within a minute or so of the pull, but then I would never get it to act up again until I did another pull and slowed down again. I never logged it since I always kind of forgot it happened until the next time it would do it, but after reading this thread it has me thinking it has to be the same issue. When it was on MAF it never happened, but I went SD due to the idle and low speed areas not behaving how I liked with the intake I have on the car. Overall the car runs much better on SD during every day driving, and the quick blip of stumble after a pull never bothered me too much, but it did make me curious as to why, and after finding this thread it makes sense.

I can also say the behavior didn't seem to change for me when I set the dynamic enable/disable to stock rpm values since I tested that out while I was on the dyno one day trying to come up with work arounds for the lack of transient fueling above 4,000 rpms, and noticed I would still get the stumble after I would do a little pull.

Also, as L1FTD mentioned about the lean spots at 1600 & 2600 on the LSA, I also have had to make some small mountains to the VVE table in those areas on my ZR1 to combat that. Unrelated to the issue in this thread I'm sure, but interesting to see it isn't just me.

Lastly, it seems that the same OS patch that fixes this issue isn't available to the ZR1 OS, so I may be stuck with it unless I 0 out the Map^2 table and hand paste the coefficients. Although compared to how severe it sounds like some cases are I may have just a very mild case of it and it is definitely livable.

[Cringer]

I know this is a few months old, but I don't come on here too often and there is a wealth of discovery in this thread. I work on mostly imports so don't use HPT too terribly much anymore, but personally own a 2009 C6 ZR1 and have noticed a good bit of the behavior mentioned in this thread. My ZR1 is tuned on speed density with a failed MAF and the dynamic enable/disable set high. Ever since going SD I would notice after a pull I would get one or two quick stumbles once I slowed down to cruising speed, usually within a minute or so of the pull, but then I would never get it to act up again until I did another pull and slowed down again. I never logged it since I always kind of forgot it happened until the next time it would do it, but after reading this thread it has me thinking it has to be the same issue. When it was on MAF it never happened, but I went SD due to the idle and low speed areas not behaving how I liked with the intake I have on the car. Overall the car runs much better on SD during every day driving, and the quick blip of stumble after a pull never bothered me too much, but it did make me curious as to why, and after finding this thread it makes sense.

I can also say the behavior didn't seem to change for me when I set the dynamic enable/disable to stock rpm values since I tested that out while I was on the dyno one day trying to come up with work arounds for the lack of transient fueling above 4,000 rpms, and noticed I would still get the stumble after I would do a little pull.

Also, as L1FTD mentioned about the lean spots at 1600 & 2600 on the LSA, I also have had to make some small mountains to the VVE table in those areas on my ZR1 to combat that. Unrelated to the issue in this thread I'm sure, but interesting to see it isn't just me.

Lastly, it seems that the same OS patch that fixes this issue isn't available to the ZR1 OS, so I may be stuck with it unless I 0 out the Map^2 table and hand paste the coefficients. Although compared to how severe it sounds like some cases are I may have just a very mild case of it and it is definitely livable.

Options:
1) If the OS patch is not available on your OS, then I think you can either:
1a) ask HPT nicely to port that over
1b) jump over to the 2bar HPT Custom OS
2) MAP^2 fix...
Unfortunately you cannot just zero these out...if you do, it will chance the shape of your VVE curve and that will impact fueling and torque calcs etc, so do not do that. But if you send me or post your tune file here, I can use the "Verlon Mode" in software to convert your normally 6 coefficient VVE shape to use 5 coefficients. The result is that MAP^2 will not be required (and zero'd out properly) while the other 5 coefficients will carry the burden of shaping the VVE.

I still maintain the issue with the LSA lean spots is due to people changing to a standard/straight spray injector, when the LSA requires an angled injector. No one believes me, nor will they put LSA injectors back in to do some simple low RPM testing to see how that changes it. And to a minor extent tuning EOIT can also help.

So...I guess I need to ask, did you swap injectors on your LS9?

[hjtrbo]

I still maintain the issue with the LSA lean spots is due to people changing to a standard/straight spray injector, when the LSA requires an angled injector. No one believes me, nor will they put LSA injectors back in to do some simple low RPM testing to see how that changes it. And to a minor extent tuning EOIT can also help.

I got a bigger bump after changing injectors.

OEM LSA Injectors tuned within a few %


DeatschWerks 65-16MX-22-1200-8 tuned within a few %


A small difference, but nothing that throws the tune off.

Edit: I cut off the graph at 8100Hz to make the bumps easier to see.

[Cringer]

I got a bigger bump after changing injectors.

OEM LSA Injectors tuned within a few %


DeatschWerks 65-16MX-22-1200-8 tuned within a few %


A small difference, but nothing that throws the tune off.

Edit: I cut off the graph at 8100Hz to make the bumps easier to see.

Is this on an LSA motor?

[hjtrbo]

Yes. Same mods for both graphs

[sgod1100]

I know this is a few months old, but I don't come on here too often and there is a wealth of discovery in this thread. I work on mostly imports so don't use HPT too terribly much anymore, but personally own a 2009 C6 ZR1 and have noticed a good bit of the behavior mentioned in this thread. My ZR1 is tuned on speed density with a failed MAF and the dynamic enable/disable set high. Ever since going SD I would notice after a pull I would get one or two quick stumbles once I slowed down to cruising speed, usually within a minute or so of the pull, but then I would never get it to act up again until I did another pull and slowed down again. I never logged it since I always kind of forgot it happened until the next time it would do it, but after reading this thread it has me thinking it has to be the same issue. When it was on MAF it never happened, but I went SD due to the idle and low speed areas not behaving how I liked with the intake I have on the car. Overall the car runs much better on SD during every day driving, and the quick blip of stumble after a pull never bothered me too much, but it did make me curious as to why, and after finding this thread it makes sense.

I can also say the behavior didn't seem to change for me when I set the dynamic enable/disable to stock rpm values since I tested that out while I was on the dyno one day trying to come up with work arounds for the lack of transient fueling above 4,000 rpms, and noticed I would still get the stumble after I would do a little pull.

Also, as L1FTD mentioned about the lean spots at 1600 & 2600 on the LSA, I also have had to make some small mountains to the VVE table in those areas on my ZR1 to combat that. Unrelated to the issue in this thread I'm sure, but interesting to see it isn't just me.

Lastly, it seems that the same OS patch that fixes this issue isn't available to the ZR1 OS, so I may be stuck with it unless I 0 out the Map^2 table and hand paste the coefficients. Although compared to how severe it sounds like some cases are I may have just a very mild case of it and it is definitely livable.

In regards to your 1600 and 2600 leans spots...you aren't the only one..lol. I've been trying to figure out the solution to this for a few years now. I'm to a point of just adding some fuel to the maf curve in the hz areas that I'm at when i go through the 2600 rpms and once I'm in PE i'm going to "rape" the table in that 2600 rpms area. I too have to have mountains like you in those two areas and even doing that it will still show slightly lean according to my STFT. Seems that no one has a true fix for it.

https://forum.hptuners.com/showthrea...2600+lean+spot

[sgod1100]

Options:
1) If the OS patch is not available on your OS, then I think you can either:
1a) ask HPT nicely to port that over
1b) jump over to the 2bar HPT Custom OS
2) MAP^2 fix...
Unfortunately you cannot just zero these out...if you do, it will chance the shape of your VVE curve and that will impact fueling and torque calcs etc, so do not do that. But if you send me or post your tune file here, I can use the "Verlon Mode" in software to convert your normally 6 coefficient VVE shape to use 5 coefficients. The result is that MAP^2 will not be required (and zero'd out properly) while the other 5 coefficients will carry the burden of shaping the VVE.

I still maintain the issue with the LSA lean spots is due to people changing to a standard/straight spray injector, when the LSA requires an angled injector. No one believes me, nor will they put LSA injectors back in to do some simple low RPM testing to see how that changes it. And to a minor extent tuning EOIT can also help.

So...I guess I need to ask, did you swap injectors on your LS9?

There is a guy on here (Jayrolla) that experienced the lean spots even with the stock injectors. He installed his headers and removed his cats while still on the stock injectors and that's when he started experiencing it.

[JayRolla]

There is a guy on here (Jayrolla) that experienced the lean spots even with the stock injectors. He installed his headers and removed his cats while still on the stock injectors and that's when he started experiencing it.

Yeah I believe that was the case. I dug through all my old logs and noticed lean spikes when I had just intake, headers and xpipe. I never did any logging before those mods to know if I was having the issue completely stock or not. Like you when I tune my MAF curve via fuel trims and AFR error I get the humps in the curve. I also get the humps in the VVE table tuning via fuel trims and the lean spikes never go away, just not quite as bad. I have also raped the PE table adding 10-15% in the 2600 area and still get 3-7% lean spike at WOT.

[sgod1100]

Yeah I believe that was the case. I dug through all my old logs and noticed lean spikes when I had just intake, headers and xpipe. I never did any logging before those mods to know if I was having the issue completely stock or not. Like you when I tune my MAF curve via fuel trims and AFR error I get the humps in the curve. I also get the humps in the VVE table tuning via fuel trims and the lean spikes never go away, just not quite as bad. I have also raped the PE table adding 10-15% in the 2600 area and still get 3-7% lean spike at WOT.

Thanks for chiming in, I thought I remembered that correctly. I'm still leaning towards reversion (thanks to Smokeshow) or some type of cat test that we can't alter.

[JayRolla]

Thanks for chiming in, I thought I remembered that correctly. I'm still leaning towards reversion (thanks to Smokeshow) or some type of cat test that we can't alter.

Man I guess I could try to install my stock intake and see what happens. Probably will try that now that weather is getting nicer.

[sgod1100]

Man I guess I could try to install my stock intake and see what happens. Probably will try that now that weather is getting nicer.

Yeah you could. I would have if I still had it...lol

[blindsquirrel]

Do you guys see the same behavior whether the MAF is still installed and plugged in but just failed in the tune, and when it's completely removed (or depinned)?