VVE Tuning lean ridge at 1800 RPM's

[MattofEarle]

I'm tuning a 2013 Sierra Extended cab 4x4
5.3L 6L80E
BTR Stage 2 truck cam
DOD & VVT Delete
1-7/8" Long Tube Headers
Catless Y-Pipe
S&B CAI

I started by adding some idle airflow and idle RPM to make sure the truck idles well enough to tune.

I also removed codes for DOD, VVT and cats as well as zero variable cam spark tables.

I reduced shift times, increased base shift pressure under light throttle and increased oncoming shift pressure slightly to get it shifting a little faster while also setting up the shift tables for the tire size and better driveability using the Bluecat tool.

I then started tuning the VVE. I unplugged the yellow MAF wire while still leaving the rest plugged in, unplugged the O2 sensors and hopefully changed the tune to run on VVE only.

I then set up an AFR500 wideband for Lambda with a graph in the scanner to report error vs. EQ Ratio while filtering out deceleration, no throttle, idle and coolant temps less than 176F. I tuned VVE in idle first before adding the idle filter.

I keep getting a lean column when logging around 1800 RPM and 2600 RPM no matter what I do it still logs lean.

I use the following filter in my graph.

([6310]<6 OR ([6310]>7 AND [6310]<14)) AND [50010.242]>176 AND [50030.91]>35

I was hoping someone could look at my tune and make sure I'm heading in the right direction and maybe help me figure out what could cause the lean ridges I keep logging or do I just need to keep going? It just looks like calculating coefficients fights me a some too.

My logs are usually over 1.5 hours now because I'm trying to get as much steady data as I can get to get it all dialed in.

Any help is appreciated.

[RobZL1]

Those ridges are typical in those areas in my experience. Just remember that VVE is a backup for the MAF for all intents and purposes, and is just one input to the dynamic air calculation. I have found you can raise those ridges up quite high, and it really makes no difference past a point. I keep the ridges, but just keep them minimal. The ridges do help to lower the lean spike when you are running VVE alone, but I find it doesn't really matter once you go back to blended, since dyn air basically tracks MAF anyway. My advice: keep the ridges but just don't go crazy with their magnitude- it will never be perfect.

Here's my current VVE on my car:

vve1.jpg

[MattofEarle]

Thanks RobZL1. I feel like I'm in an endless circle with trying to get them smooth as it keeps screwing with the surrounding cells. I'm on version 36 of trying to tune the VVE. I'd say it is about as good as it is going to get and time to start on the MAF then idle tuning.

[07GTS]

because the vve is a just a calculation it may never be smooth as it has to work in the coefficients, if u can do proper VE u can get them smooth and also remember transient fuel is there to compensate for throttle movements that the vve and ve arnt designed to do so if u have a peak in the vve where u are always getting in the throttle u may need more transient fuel so u can then lower the peak

[h2.4]

I have seen that with cammed vehicles for sure. Just remember to give the engine what it wants. I have chased my tail when trying to tune a smooth Vve. I end up going back and the engine needed those ripples to keep fueling in check.

[sgod1100]

vve graph.png

yyup, i have the same thing going on as well.. I was doing the same thing as you trying to get the vve smooth but i realized that wasn't what the engine wanted . Ignore that my fuel drops after 3k rpm as that is when i'm maf only...lol. this is on a 2014 ctsv

[MattofEarle]

Thanks for the confirmation everyone. I fought it on my 2015 and now this truck trying to get a smooth graph. I'll just give her what she wants and see how it goes.

[cmitchell17]

Thanks for the confirmation everyone. I fought it on my 2015 and now this truck trying to get a smooth graph. I'll just give her what she wants and see how it goes.

I think you saw my VVE graph in my thread and I have the same thing. Although it recently popped up here after I started doing more logging again and especially after switching from using the AEM wideband to using LTFT+STFTs.

My question is why do we put so much trust into a wideband reading that already has error from all kinds of different variable, fuel quality, MBT timing being off effecting combustion, compression changes, bigger cams causing combustion issues, etc.? I realize there is no other cheap way so I guess that's the reason. You would think by now we would have some new technology thats cheaper, I remember back in late 2000s they were talking about cheap in cylinder pressure transducers coming not sure what happened there. I know the new C8 LT2 has a wideband at least, too bad those are untuneable.

[jsllc]

When you modify VVE formulas with math the outcome is cleaner. All my tunes are done from MAF calcs and translated to VVE. Never even run the car without the MAF until the end just to test the outcome.

vve.png

[MattofEarle]

When you modify VVE formulas with math the outcome is cleaner. All my tunes are done from MAF calcs and translated to VVE. Never even run the car without the MAF until the end just to test the outcome.

vve.png

Tell me more.

[RobZL1]

do a search for the GMVE formula on here, lots of good info. It lets you build a VVE chart while tuning the maf. You can also auto-correct it with your wideband data in one pass in the same formula if you like. I know Scott's right on the smoothing, but like I said above, I have found the peaks actually help fueling when running VVE only. Not that it matters much, since you know, I never do that. bear in mind we're also looking at HPT's interpretation of the surface from the patched-quilt equations. I'd bet boundary conditions aren't perfectly displayed anyway.

[07GTS]

are your peaks running along VVE zone boundary's ? u can adjust them so its more linear over the table, jumping thru zones would have to create some calculation so if u broaden them could help smooth the transition

[jsllc]

do a search for the GMVE formula on here, lots of good info. It lets you build a VVE chart while tuning the maf. You can also auto-correct it with your wideband data in one pass in the same formula if you like. I know Scott's right on the smoothing, but like I said above, I have found the peaks actually help fueling when running VVE only. Not that it matters much, since you know, I never do that. bear in mind we're also looking at HPT's interpretation of the surface from the patched-quilt equations. I'd bet boundary conditions aren't perfectly displayed anyway.

Exactly right. Anyone who runs VVE only is looking for issues. Not how the ECM was designed.

You will want to start by adjusting the Zone MAP and Zone RMP boundaries to mach how you want the resolution and zones to be calculated. Then you will build your graph in the scanner to match the pic using both Cylinder Air Mass and Dynamic. A gen4 ALWAYS uses dynamic with a bias towards VVE or MAF depending on the settings. Good thread below. There are some that give formulas. Resolution is a must so use the examples posted. I use CylAirMass to validate against my injector data. It should be close if it is not the injector data is not correct. I use Dynamic to tune the VVE. My formulas create both percent of error on one and actual calculated value on another. When you have it right VE Air, Dyn Air, and MAF air will all be VERY close to the same.vve-4.png

https://forum.hptuners.com/showthread.php?8490-SD-tuning-for-E38-E67-ECM-s/page3&highlight=GMVE

vve-3.pngvve-2.png