[ZLRob]

Originally Posted by KingLT1

brake torque management

I disabled that from what I remember.

Originally Posted by radz28

Driver Demand tables?

Maybe... I notice a momentary spike of timing for no reason in the logs accompanied with a lean spike of 14% on both banks when it occurs.

[raptor5244]

Originally Posted by d15b7

It sounds like you guys are losing brake boost assist. You aren’t left foot braking are you?

That is a good way to describe it. No left foot braking. It can happen in any drive mode. Always at low speed when coming to a stop. The brake pedal feels normal when it happens but it does freak out out as you have to apply quite a bit of brake force to overcome what feels like a momentary engine surge.

[radz28]

I can tell you that the tuning plays a big part in how the car behaves, and the wrong changes, even small, can have a big impact.

I was playing with the DD tables once, and made a relatively small change where I shouldn't, and the car, literally, nearly drove me off the road, AFTER I left off the gas. I went across 5-lanes of traffic it was so bad. Obviously - I was lucky.

If someone's messing with any of the torque tables, this can have an effect on this kind of behavior. If you tell the car to "make" too much torque, it's going to try. If you don't tell it to "make" the proper amount, you'll get throttle and spark issues. Finding a balance, from the software we have available to us, is key, and calibrating air flow is the most important place to start. Once air flow is calibrated, the ECM knows what TQ it's producing, and a lot of the rest can start falling into place.

[Katech_Zach]

Sounds like you are blowing through the torque converter. Common with cars that have large cams and a stock converter (gets very tricky). Assuming you have a stock cam, I would check the tune

[ZLRob]

Originally Posted by radz28

I can tell you that the tuning plays a big part in how the car behaves, and the wrong changes, even small, can have a big impact.

I was playing with the DD tables once, and made a relatively small change where I shouldn't, and the car, literally, nearly drove me off the road, AFTER I left off the gas. I went across 5-lanes of traffic it was so bad. Obviously - I was lucky.

If someone's messing with any of the torque tables, this can have an effect on this kind of behavior. If you tell the car to "make" too much torque, it's going to try. If you don't tell it to "make" the proper amount, you'll get throttle and spark issues. Finding a balance, from the software we have available to us, is key, and calibrating air flow is the most important place to start. Once air flow is calibrated, the ECM knows what TQ it's producing, and a lot of the rest can start falling into place.

Originally Posted by Katech_Zach

Sounds like you are blowing through the torque converter. Common with cars that have large cams and a stock converter (gets very tricky). Assuming you have a stock cam, I would check the tune

That's the thing. The Driver Demand tables are stock currently and the cam is all stock. The only change is a 5% supercharger pulley and an ATI super damper to run the engine accessories. Timing tables have not been modded on the low end but it is notable that torque management is causing the timing to spike coming to a stop, but it's only in manual mode while in first gear though. If I throw it in automatic and come to a stop without using the shifter or paddle shifters at all I won't feel the runaway feeling from the engine because the transmission is still in second gear by the time I reach the stop.

I've managed to confine the issue to a singular very specific scenario event but I can always replicate it. It's not a sometimes thing, it's an all the time thing if I'm in paddle shift manual mode and coasting down in first gear.

[radz28]

Would it be easy to describe or characterize what you have changed for these mods'? I saw you mention Flex-tuned, so I imagine your car is tuned. If you haven't looked already, I might also see if your Virtual Torque tables have been adjusted. It's hard to say not being able to see the tune or a scan, but if you're tuner touched anything air flow related, it could be your VTT idle areas could have moved around. I doubt your mods' might require that, but in the event someone changed them from stock, it could be that's something to look into. Again - I wouldn't think that would be necessary for your list of mods', but I wouldn't know what your tuner did or didn't touch.

VTT will influence idle. A calibrator who helped me said that he liked seeing TMA pull around 10* of timing at idle, just so it's doing it's job, and had enough timing swing to add or pull torque to achieve the desired idle speed. Of course, there needs to be a minimum advance so you don't melt cats and such, but I'm just saying VTT is very important for idle, and if that's not shaped correctly, you can have some naughty behavior.

Also - have your Driver Demand Increasing/Decreasing Immediate/Predicted torque rates been moved around or anything? There's a TUTD function in those, too.

[raptor5244]

Originally Posted by ZLRob

That's the thing. The Driver Demand tables are stock currently and the cam is all stock. The only change is a 5% supercharger pulley and an ATI super damper to run the engine accessories. Timing tables have not been modded on the low end but it is notable that torque management is causing the timing to spike coming to a stop, but it's only in manual mode while in first gear though. If I throw it in automatic and come to a stop without using the shifter or paddle shifters at all I won't feel the runaway feeling from the engine because the transmission is still in second gear by the time I reach the stop.

I've managed to confine the issue to a singular very specific scenario event but I can always replicate it. It's not a sometimes thing, it's an all the time thing if I'm in paddle shift manual mode and coasting down in first gear.

FWIW, my 2021 ZL1 was bone stock and did what you describe.

[ZLRob]

Originally Posted by radz28

Would it be easy to describe or characterize what you have changed for these mods'? I saw you mention Flex-tuned, so I imagine your car is tuned. If you haven't looked already, I might also see if your Virtual Torque tables have been adjusted. It's hard to say not being able to see the tune or a scan, but if you're tuner touched anything air flow related, it could be your VTT idle areas could have moved around. I doubt your mods' might require that, but in the event someone changed them from stock, it could be that's something to look into. Again - I wouldn't think that would be necessary for your list of mods', but I wouldn't know what your tuner did or didn't touch.

VTT will influence idle. A calibrator who helped me said that he liked seeing TMA pull around 10* of timing at idle, just so it's doing it's job, and had enough timing swing to add or pull torque to achieve the desired idle speed. Of course, there needs to be a minimum advance so you don't melt cats and such, but I'm just saying VTT is very important for idle, and if that's not shaped correctly, you can have some naughty behavior.

Also - have your Driver Demand Increasing/Decreasing Immediate/Predicted torque rates been moved around or anything? There's a TUTD function in those, too.

What is TUTD?

The Driver Demand tables were modified by someone who owned it before I did but I set them back to stock. The same issue occurs. I just checked the Virtual Torque and even the Virtual VE tables and found they have been untouched compared to the OE tune stock file.

You know, when I see the issue happening I see TMA pulling as much as 11.5 degrees before it ever gets to idle. When that occurs I see timing jump from 10 degrees to 14.2 degrees which is not terrible, but something is up for sure. I'll attach a screenshot of the event so you can see what the primary event looks like.

Originally Posted by raptor5244

FWIW, my 2021 ZL1 was bone stock and did what you describe.

It's frustrating isn't it? The issue is being narrowed down on mine and it has been found that it is Torque Management making the PCM pull too much timing for the brief moment the issue occurs and it is evidenced by a sharp spikes in the Torque Management and timing advance graphs the moment it happens. We can't figure out why it's happening though.

[Megahurtz]

Did you disable Fast Exit Torque by chance?

[Idaho2018GTPremium]

Haven’t read all the responses, but just speculating, could it possibly be a transmission issue? Like the converter locking up or something when it shouldn’t?

[ZLRob]

Originally Posted by Megahurtz

Did you disable Fast Exit Torque by chance?

I did, but it makes zero difference with it enabled or disabled. It's the same thing.

Originally Posted by Idaho2018GTPremium

Haven’t read all the responses, but just speculating, could it possibly be a transmission issue? Like the converter locking up or something when it shouldn’t?

If it was doing that wouldn't that be a command issue? That's something I've been considering, like an issue on the transmission side of tuning, but have not actually tracked anything really on it yet.

[Jus Cruisin]

Any engine rpm surge when this happens?

[raptor5244]

Have you tested with and without the AC on? I think I noticed it more when the AC was on.

[ZLRob]

Originally Posted by Jus Cruisin

Any engine rpm surge when this happens?

Zero flare or surge when it occurs. The RPM is very smooth and linear the entire time.

Originally Posted by raptor5244

Have you tested with and without the AC on? I think I noticed it more when the AC was on.

It'll do it either way. It's still just as noticable too. Though now that you mention it that is something I will have to look at it harder to make sure it doesn't make a difference.