lean area around 2500ish rpms-2014 ctsv

[sgod1100]

I'm sorry for not being completely read into this problem but could someone give me a summary?

I've done a ton of CTS's and LSA's. I actually even did the first production LSA CTSV ever made for Rick Hendrick before they were out. I personally daily drive a '17 SS with a LSA. Never noticed any lean spikes. The VVE table will have a hump at lower RPM/high boost that falls a bit before taking back off. I also set most up in SD only because you can hit the same spot in the MAF passing someone on freeway with 6th gear/locked TCC and be lean but rich if you did a standing start full throttle pull.

Those having problems... have you tried going 100% SD?

Turn off injector desoot mode?

The VVE table will definitely look different than a NA, centrifugal, or turbo.. but similar to any other whipple/magnacharger VVE table.

going 100% SD- yes lean spot still there
turn off injector desoot mode- Mine has been off since I bought the car in 2015

It seems that it only has happened to a handful of us. However Jayrolla uncovered a few ctsvs on the dyno and right at 2600 rpms they go lean then go right back to commanded (post #482)

Here's what it looks like...ignore the KR this a very old snapshot of a log. Notice the maf and VE airflow is actually higher than DYN air at that point.

2600 rpm lean spot.JPG

[L1FTD]

Attached are two VVE tables from the last two CTSV's I did.. My notes say one was a 388 with 231/247 duration cam 1300 ID injectors

The other was a stock CID 223/235 1050 Id injectors

I don't even remember the cars to be honest. I just wanted to show what I find to be a typical looking VVE table for a LSA or really any PD style blower.

Attachment 144563Attachment 144564

Heres an example of the VE and a snap of log.

AFR target a little lean here, but can see the massive peaks needed to keep the AFR on track.

Cylinder airmass shoots up as a result, but car drives smooth despite this.

This is the HPT 2Bar OS, no VVE, no MAF.

Screenshot (34).png WOT.png

[Alvin]

Heres an example of the VE and a snap of log.

AFR target a little lean here, but can see the massive peaks needed to keep the AFR on track.

Cylinder airmass shoots up as a result, but car drives smooth despite this.

This is the HPT 2Bar OS, no VVE, no MAF.

Screenshot (34).png WOT.png

In my opinion those peaks aren't unusual except they should be interpolated between the two and carried to 0 RPM. Look at the VVE tables I posted. That shape is pretty common with all PD style blower.. And not like turbo, centrifugal, or NA

[hjtrbo]

This is important.

L1FTD and I have virtually identical cars. Same base OS. Similar power levels. Different aftermarket components. I don't have this issue. Just got lucky. If L1FTD was in a position to re-install his maf and revert the OS back then we would be near twins save for injectors and cam grind.

[sgod1100]

This is important.

L1FTD and I have virtually identical cars. Same base OS. Similar power levels. Different aftermarket components. I don't have this issue. Just got lucky. If L1FTD was in a position to re-install his maf and revert the OS back then we would be near twins save for injectors and cam grind.

Really wish I was one of the lucky ones....lol.

[sgod1100]

In my opinion those peaks aren't unusual except they should be interpolated between the two and carried to 0 RPM. Look at the VVE tables I posted. That shape is pretty common with all PD style blower.. And not like turbo, centrifugal, or NA

so, if you interpolate then the area between 1600 and 2600 is going to be very rich. Would you just leave it like that?

[hjtrbo]

Really wish I was one of the lucky ones....lol.

Cryptically what I'm trying to say is there's a combo of parts and / or a tuning strategy (mafless, custom os etc) that has to be causing this. I can't imagine in stock form this problem existing at the oem. If any of you could take a hit for the team and roll changes back towards stock both mechanical and tune and share the findings here, I think that knowledge would be extremely valuable should it prove that this problem is self induced and more importantly what component or strategy influences it the most.

[L1FTD]

In my opinion those peaks aren't unusual except they should be interpolated between the two and carried to 0 RPM. Look at the VVE tables I posted. That shape is pretty common with all PD style blower.. And not like turbo, centrifugal, or NA

I was running the VVE before I switched to 2Bar OS, still SD. I had more interpolation between the peaks, like a little hammock, not as dramatic. It was just harder to get the fuelling right, adding so much fuel to a column would pull the surrounding up. Always ended up rich before and after the lean spike.

Switched to the 2Bar to hit the lean spikes exactly, no interference from coefficient calculations.

The massive peaks work well, gets the fuelling spot-on before/during/after lean spikes, drivability surprisingly not affected.

The thing is, it just seems so unnatural? Like a diagnostic? Or mechanical interference?

In the space of 200rpm, the fuel demand shoots up 15%, then right back down? Twice.

This is important.

L1FTD and I have virtually identical cars. Same base OS. Similar power levels. Different aftermarket components. I don't have this issue. Just got lucky. If L1FTD was in a position to re-install his maf and revert the OS back then we would be near twins save for injectors and cam grind.

You are a very lucky man!

Piecing it all together, it seems the bigger HP cars dont experience this, or at a lesser extent.

Bigger HP on the LSA usually means getting rid of the factory FSCM and doing some further fuel system upgrades.

The ID1050?s only ever see a max of 50% duty cycle. Thats probably not helping me.

[07GTS]

just a thought but when this is tested with the vve does zeroing or changing the ''prediction coefficients'' help it at all ? i know most dont touch that so a predicted event could always be happening no matter the vve adjustments ? just throwing a thought out there

[L1FTD]

Cryptically what I'm trying to say is there's a combo of parts and / or a tuning strategy (mafless, custom os etc) that has to be causing this. I can't imagine in stock form this problem existing at the oem. If any of you could take a hit for the team and roll changes back towards stock both mechanical and tune and share the findings here, I think that knowledge would be extremely valuable should it prove that this problem is self induced and more importantly what component or strategy influences it the most.

Its hard to keep track, but its been narrowed down by members here.

Problem exists in blended, MAF only (not possible, but anyway), VVE SD, 2Bar SD.

Problem exists on an LS9 ZR1, stock exhaust/o2, big injectors only mod.

And my first sighting of it, after intake, headers, no cats, stock injectors.

Between my car and the LS9, we almost cancel each other out back to stock. He has injectors as only mod, I have intake/exhaust as only mod (stock injectors). Both have the problem.

I know what you mean, it could be a simple tune thing, maxing a table that shouldnt be or something. Theres just so many guys with the same problem.

Ill have a close compare of mine and your tune, try a few things that stick out.

[Alvin]

so, if you interpolate then the area between 1600 and 2600 is going to be very rich. Would you just leave it like that?

I wouldn't think that is the case. The ones I show don't cycle rich/lean.

One thing I want to point out too which might be the whole cause of the confusion.

This area you guys are talking about is very susceptible to transients. Its really hard to be steady state under heavy load at 2500 RPM if its not a manual trans. So if you aren't carefully filtering out quick pedal movements or fast MAP changes you're going to see lean spots just because it is a transient. If you move the pedal quickly.. there will be a fraction of a second where the WB will show lean. This is OK and not something you could really fix.

When I'm dialing in this area I'll take the car to the freeway where I can run 80 mph.. Manually shift into 6th gear (AUTO) with the TCC locked up.. Start at 60 mph, lean into the throttle to make say 140kpa, then same thing but at 160 kpa, then full boost, etc.

but as steady as possible is the name of the game.

[L1FTD]

just a thought but when this is tested with the vve does zeroing or changing the ''prediction coefficients'' help it at all ? i know most dont touch that so a predicted event could always be happening no matter the vve adjustments ? just throwing a thought out there

Ive currently got them ?zeroed?. Theyre not all zero, but ive removed the coefficients, so to speak.

All MAP and TPS are zero. Current and Old are zero. Corrected is zero. Base is 1.

Ive tried stock prediction, and changing the coefficients in the zones the lean spikes exist.

No change to lean spikes, just tip-in as expected.

[L1FTD]

I wouldn't think that is the case. The ones I show don't cycle rich/lean.

One thing I want to point out too which might be the whole cause of the confusion.

This area you guys are talking about is very susceptible to transients. Its really hard to be steady state under heavy load at 2500 RPM if its not a manual trans. So if you aren't carefully filtering out quick pedal movements or fast MAP changes you're going to see lean spots just because it is a transient. If you move the pedal quickly.. there will be a fraction of a second where the WB will show lean. This is OK and not something you could really fix.

When I'm dialing in this area I'll take the car to the freeway where I can run 80 mph.. Manually shift into 6th gear (AUTO) with the TCC locked up.. Start at 60 mph, lean into the throttle to make say 140kpa, then same thing but at 160 kpa, then full boost, etc.

but as steady as possible is the name of the game.

sgod1100, myself, and most of the other gentlemen here are M6 trans. I believe.

I can go WOT from 1000rpm, and lean spikes show up the same.

[sgod1100]

sgod1100, myself, and most of the other gentlemen here are M6 trans. I believe.

I can go WOT from 1000rpm, and lean spikes show up the same.

Yes, that's correct. I've been steady state in those areas many times and they will still show up as lean

[PGA2B]

I have an A6 and don't notice it as much when I am not in manual mode. The stock A6 shift points take into consideration these spots I feel. In manual mode, I can reproduce the lean spots everyone is seeing.

[JayRolla]

This is pretty much how mine came out. And yes if I interpolated between the humps I would be rich in-between the lean spikes at those two rpm points. Even with these humps and little humps in the MAF curve I still go slightly lean. You dont feel it as much but can be seen on the WBO2 and yes I am steady state throttle.

I also had this issue on stock injectors. Just intake, headers, xpipe, no cats.

[JayRolla]

Race Proven Motorsports posted a new 5th gen ZL1 video. Same issue. So it looks like this is pretty much happening to all these motors. I reached out to Fran the tuner/owner and he said he doesnt see this as a bad lean spike at WOT and to email him this thread but he never got back to me. Im just going to move past this and not worry about it. Peaks in the VVE, MAF tables, raped PE table.

[L1FTD]

Race Proven Motorsports posted a new 5th gen ZL1 video. Same issue. So it looks like this is pretty much happening to all these motors. I reached out to Fran the tuner/owner and he said he doesnt see this as a bad lean spike at WOT and to email him this thread but he never got back to me. Im just going to move past this and not worry about it. Peaks in the VVE, MAF tables, raped PE table.

I watched this video after you mentioned it.

False alarm, there is no lean spike! None of us have a lean spike!

He was certainly dismissive of your comments. To the point of even denying the AFR spiked lean at the rpm youre talking about.

Anyway, I agree. If the fuel is getting there one way or another, all is well.

[sgod1100]

I watched this video after you mentioned it.

False alarm, there is no lean spike! None of us have a lean spike!

He was certainly dismissive of your comments. To the point of even denying the AFR spiked lean at the rpm youre talking about.

Anyway, I agree. If the fuel is getting there one way or another, all is well.

pfftt..doesn't see it? or IGNORING it? lol.

[sgod1100]

Race Proven Motorsports posted a new 5th gen ZL1 video. Same issue. So it looks like this is pretty much happening to all these motors. I reached out to Fran the tuner/owner and he said he doesnt see this as a bad lean spike at WOT and to email him this thread but he never got back to me. Im just going to move past this and not worry about it. Peaks in the VVE, MAF tables, raped PE table.

13.5 AFR with 9.5 lbs of boost...yeah no big deal..lol