VVE Tuning Lean spikes

I'm having these crazy issues when trying to tune VVE on my 2017 Camaro SS. I swapped a LT2 intake manifold, ported the manifold and stock TB myself and added LT headers.

The baseline tune seemed pretty close (as it probably should be) but I wanted to do it right. Followed Goat Rope Garage speed density tuning video and also checked on here to see common issues.

My main concern is in the 2200-2600 rpm area where the baseline is nowhere close. I'm getting some crazy heavy lean spikes and it's scaring the crap out of me. I keep bumping the VE table up locally but its almost getting more and more lean the more I change it. I'm wondering if this is a sign of something mechanical that is wrong? I would have thought a vacuum leak would have made it rich? Or are my adjustments doing something ill intended? Parking the car until I have an idea of what's going on. Go easy on me if its something stupid on my part.

Unfortunately I forgot to save the most recent log where its only getting more severe but I'll leave a log with the corresponding cal, and then a cal with my changes that got worse. Look at the 20:51:24 for me cruising in 4th gear to see the lean spikes. I'll also leave a list of all the changes I made from the baseline tune below to start tuning VE.

Changes to tune VE
Engine - Fuel - Cutoff DFCO

Enable RPM 1300 --> 8100
Disable RPM 1200 --> 1


Engine - Fuel - Temp control

COT Disable


Engine - Fuel - Oxygen Sensors

O2 readiness V -->made negative


Changed Manifold volume to 16000cm3 old was 13420cm3
Google claims Lt1 11,100 cm3, LT2 14,100 cm3 so I just changed it so its a similar the delta from LT1 to LT2


Engine Diag - Airflow - MAF Sensor
MAF Freq Fail High 14500 --> 1
MAF Freq Fail Low 500 --> 0

DTC's
P0101-0103 mil on second error --> mil on first error

Engine - Spark - Advance
Added -5 to all in base High Octane & High Octane DP tables

You need to tune the MAF as well in the same area.

Change manifold volume back to stock.

I just back calculated your VE table based off of your log - it turned out looking like a swinging hammock. Honestly the only time I've ever seen numbers that low and air acting that goofy is when there was something wrong with the engine such as a dead cylinder or bent valve causing serious reversion... Hopefully it's just your manifold volume setting as that does change your ve calculations. I don't think what you did to it would have hurt airflow, but that's up to you to know whether or not it feels that much weaker or not.

You may even want to do a write entire and recheck things - that log has a few things such as ivt that goes from reading 246c to -200something Celsius. Data definitely doesn't look right.

Quote:

---

Originally Posted by GHuggins

Change manifold volume back to stock.

I just back calculated your VE table based off of your log - it turned out looking like a swinging hammock. Honestly the only time I've ever seen numbers that low and air acting that goofy is when there was something wrong with the engine such as a dead cylinder or bent valve causing serious reversion... Hopefully it's just your manifold volume setting as that does change your ve calculations. I don't think what you did to it would have hurt airflow, but that's up to you to know whether or not it feels that much weaker or not.

You may even want to do a write entire and recheck things - that log has a few things such as ivt that goes from reading 246c to -200something Celsius. Data definitely doesn't look right.

---

O boy that doesn?t sound good. I?ll just just go back to my stock baseline and carefully retrace my steps. I?ll also do a leak-down for my sanity?s sake.

Edit* the ivt looks to be a known issue on some of the gen 5's. I think I just might be one of those impacted?
https://forum.hptuners.com/showthrea...temp-need-help

The thumbnails of your VVE surfaces look ridiculous. VVE should be smooth and progressive when it matches the engine. Whatever method you are using to get those mountains/valleys is not helping you.

Quote:

---

Originally Posted by eficalibrator

The thumbnails of your VVE surfaces look ridiculous. VVE should be smooth and progressive when it matches the engine. Whatever method you are using to get those mountains/valleys is not helping you.

---

First off I 100% agree with you. The higher pressure ratios/rpms is how it was read off the vehicle stock. Those look pretty odd already but its N/A so above 1 doesnt really matter.

The peaks its making is just by logging a correction factor and applying multiple by percent-halt. I try to do my own smoothing but I keep making the surrounding areas overly rich but it doesnt fix the lean spike thats localized at 2200-2800 rpms and at .5-.85 pressure ratio. That little section just never seems rich enough to ever get close to 1 lambda.

Checked the car for physical issues and even ran it back on the stock cal and everythings fine. Its just once I disable closed loop and the MAF to get to solely speed density, thats when it spikes in this range.

Don't disable closed loop. You can fail the maf without issue on most of the gen 5's. If I get time tonight I'll post a math formula to back calculate the VE table to get you close before you even have to fail the maf to do the fine tuning on the VE table.

So you have a very similar setup to me, and people might disagree... I've been down the same exact road you are going down and basically you are tying too hard. The best advice I got lately is to put the VVE back to stock, put MAF curve back to stock and tune roughly from 5000ish hertz and up. This is what I have done, and it brought my part throttle fuel trims right in line, and car runs better than when I was trying to adjust the VVE. With car being torque biased adding the airflow down low makes torque management very intrusive, especially without adjusting VTT. Fuel trims being spot on tells you your fueling is good, since the wideband is really better at WOT.
Put you manifold volume to stock. You will have to adjust your Map Virtual torque table. Increase 100 kpa line to roughly the torque your engine is making at the corresponding spark at WOT. I increased mine another 40/50 ft/lbs and then interpolate to the lower 20kpa line. This made the car run so good, and shift sooooo much better. Torque management is not nearly as intrusive now.
My issue was always running way too rich, so if you have lean spikes I would verify your install of the LT2 is correct. Watch my video on youtube to show you the steps I took. There is a little alignment knob that has to be ground down for it to sit on the heads right. Also the foam piece can mess with you.

Quote:

---

Originally Posted by essmotorsports

So you have a very similar setup to me, and people might disagree... I've been down the same exact road you are going down and basically you are tying too hard. The best advice I got lately is to put the VVE back to stock, put MAF curve back to stock and tune roughly from 5000ish hertz and up. This is what I have done, and it brought my part throttle fuel trims right in line, and car runs better than when I was trying to adjust the VVE. With car being torque biased adding the airflow down low makes torque management very intrusive, especially without adjusting VTT. Fuel trims being spot on tells you your fueling is good, since the wideband is really better at WOT.
Put you manifold volume to stock. You will have to adjust your Map Virtual torque table. Increase 100 kpa line to roughly the torque your engine is making at the corresponding spark at WOT. I increased mine another 40/50 ft/lbs and then interpolate to the lower 20kpa line. This made the car run so good, and shift sooooo much better. Torque management is not nearly as intrusive now.
My issue was always running way too rich, so if you have lean spikes I would verify your install of the LT2 is correct. Watch my video on youtube to show you the steps I took. There is a little alignment knob that has to be ground down for it to sit on the heads right. Also the foam piece can mess with you.

---

So ESS was right in a sense. I took the manifold off and saw some witness marks that the high pressure pump was rubbing against the intake interfering not making a perfect seal but a good enough to run decent. There?s ribs in that area that I ground down but not well enough to make the LT2 manifold fit on an LT1. I took a few images snaking my phone on the backside and there is like a 1-2mm gap between the manifold and head. Just enough to see and matter but not enough to notice from just looking at it from any other view.

My guess why it only showed in certain RPMs is maybe scavenging forces were strong enough to break the seal? Who knows.

Either way I feel a little foolish and 90% sure this should fix my problem. Hopefully this thread helps someone with similar problems in the future.

Vacuum leaks do some weird things on these torque biased ecu's.

Sorry, but I forgot about posting this as I was working late the last few nights. You can use this - the more you hit the same cells the more accurate - I have seen within a 1 to 3 % error and up to 12 or so % with far less quicker cell hits. This way you can tune in your VVE whilst tuning in your maf at the same time.

(([50041.223]*(273.15+[50011.241]) * (1000/[50030.91]))

Not sure if this will matter, but shouldn't the DFCO be Engine - Fuel - Cutoff DFCO

Enable RPM 1300 --> 8100
Disable RPM 1200 --> 8000

You want DFCO and CFCO disabled. Maybe the Gen V is different.

You can rescale your VVE to be easier to read by selecting the 10-105 kpa scale in the defaults drop down. Open VVE Table editor and put the curser over the Manifold Absolute Pressure (kpa) row axis. you'll then see the Axis Creator there. Select the 10-105 and then look at the 3d graph again.

It looks rediculous on the stock ZL1 in 3 bar as well. No Idea why GM did that but it can be smoothed even if you never plan to reach that load cell

Tip of the Day:

For MILD mods that require MILD VVE changes(no heads cam), only change one zone at a time to get you into the ball park. Then you can go back and smooth some of the transitions if needed. But honestly, without a heads/cam change, I have never found the need to completely rework and smooth the VVE table. I maintain GM's block like nature. The only time I smooth the VVE table to look like a nice wave is when the car has cam and it is locked at 0 or 0-4. Not saying I'm right, but its worked for me.

Quote:

---

Originally Posted by TriPinTaZ

Tip of the Day:

For MILD mods that require MILD VVE changes(no heads cam), only change one zone at a time to get you into the ball park. Then you can go back and smooth some of the transitions if needed. But honestly, without a heads/cam change, I have never found the need to completely rework and smooth the VVE table. I maintain GM's block like nature. The only time I smooth the VVE table to look like a nice wave is when the car has cam and it is locked at 0 or 0-4. Not saying I'm right, but its worked for me.

---

I've found the same to be true. I've actually gone in behind some tuners that dialed it in on stock motors that were having fuel cut problems and everything else. Plays havoc on the torque models.

Quote:

---

Originally Posted by jakeb2011

So ESS was right in a sense. I took the manifold off and saw some witness marks that the high pressure pump was rubbing against the intake interfering not making a perfect seal but a good enough to run decent. There?s ribs in that area that I ground down but not well enough to make the LT2 manifold fit on an LT1. I took a few images snaking my phone on the backside and there is like a 1-2mm gap between the manifold and head. Just enough to see and matter but not enough to notice from just looking at it from any other view.

My guess why it only showed in certain RPMs is maybe scavenging forces were strong enough to break the seal? Who knows.

Either way I feel a little foolish and 90% sure this should fix my problem. Hopefully this thread helps someone with similar problems in the future.

---

Glad you got it figured out! 👍🤘