[big dave]

I'm wondering at what point after you start modding the ZL1 will it be necessary to get a TCM tune? Primarily what is it for? To save the tranny? Where are the gains seen after the tune? 60', between shifts. etc...?

[Jaxcam02]

With an automatic transmission. Anytime you touch the tune for the engine you need to be messing with the transmission too.

Your shift points, torque management, etc all need to be adjusted when the engine tune is adjusted. I am sure you could get away with leaving the transmission tune alone in some cases. But why would you not fine tune it when you touch the engine tune.

[radz28]

If I recall, for cars up to 2020 (yours doesn't appear to be), you can send your TCM to HPTuners to be unlocked, and then begin tuning. If I had the ability to do that, I would have, as soon as I mod'd. Unless you need to change the airflow/torque/spark/etc. model, you'll probably be okay. It is my understanding VVE is near the top of the tuning that needs to be correct, because a lot of how the car shifts depends on airflow, fueling, etc. for the torque model, which influences the tranny significantly. A lot of guys that are heavily mod'd don't even tune VVE, or only tune where they need to, and leave as much stock as possible. I'm not sure you need to really get into the TCM until you move through FBOs, but there seem to be two primary trains of though (leave VVE stock if you need to/tune VVE).

Personally - it sounds like there are some people who post here once-and-a-while that have ONLY tuned the TCM and have made great strides in better performance at the track, without getting into the engine side. It seems to me that either the PCM or the TCM will intervene if the car starts making more than "allowable" torque limits; it will start pulling spark, fuel, or throttle plate, depending on if it thinks in needs to react quickly, or not (spark/fuel is quickest at pulling power, when it thinks it needs to do so). You can (apparently) safely pull how much spark retard there is between shifts, to quicken them (to a point), and adjust pressure and all that. But it seems to me if your fueling/timing/torque models are all within (relative) line of each other, the car is going to shift as it needs to, and apply as much pressure as it needs to to hold together (up to a certain point, obviously). That's pretty much the logic I'm going by (I'm NO expert). You can lie to the car (essentially) and make it think it's making more torque than it is, and make the tranny behave differently, but it doesn't mean it's a dynamic improvement. If you want to try to bark the tires on the 2-3 shift at 60, you could likely kick the rear end out, in the middle of an interchange turn or something and loose control (for example), or just make the car shift harder and just beat on the rest of the driveline just because you might think the quickest/hardest shift is always best for heat and wear (what I'm trying to say is upset the car, and lose control in some circumstances). Each person has their idea of what they think their car should shift like, so that might be where you want to start (if you don't already have an idea what you want).

If you're going to crack you warranty open, you might as well get the most out of the car. Personally - I wouldn't add power without proper tuning and that includes the transmission. All of this torque logic is fairly complicated with how all the systems dance with each other. I'd look for a tranny tune from experienced guys over at HPTuners (there are a few of those guys that post here, too) and go at it after FBOs.

I am still learning a lot, so sorry if I bounced around in my comments. I wouldn't call them answers because I wouldn't try to suggest my logic is better than a lot of others in our Community.

[big dave]

Thanks for the replies. The reason why I was wondering where the car picks up is because after my TCM/PCM tune, I'm seeing very little to no improvement in 60' over stock. According to the dyno, I picked up a considerable amount of torque after getting tuned for E50, but to me it isn't reflected in the 60'. Looking at the logs, it looks like TM is seriously killing the power down low.

[Jaxcam02]

Originally Posted by big dave

Thanks for the replies. The reason why I was wondering where the car picks up is because after my TCM/PCM tune, I'm seeing very little to no improvement in 60' over stock. According to the dyno, I picked up a considerable amount of torque after getting tuned for E50, but to me it isn't reflected in the 60'. Looking at the logs, it looks like TM is seriously killing the power down low.

What is the torque management set to? Your probably going to have to open it up a bit.

[2018ZL1]

Originally Posted by big dave

Thanks for the replies. The reason why I was wondering where the car picks up is because after my TCM/PCM tune, I'm seeing very little to no improvement in 60' over stock. According to the dyno, I picked up a considerable amount of torque after getting tuned for E50, but to me it isn't reflected in the 60'. Looking at the logs, it looks like TM is seriously killing the power down low.

What kind of tires are you running out back Dave??

[Z OH 6]

Who is the tuner?

[big dave]

Originally Posted by 2018ZL1

What kind of tires are you running out back Dave??

Nitto NT05R2. The tires aren't the problem, they're dead hooking. I have several high 1.6 60' times on the stock tires with the car being completely stock. I figured an extra 90 lbs of torque would get me in the high 1.5 range with drag radials.

[DangerZL1]

How do you get around this problem in a modded 20/21 where the TCM is not tunable?

[wnta1ss]

Originally Posted by big dave

Thanks for the replies. The reason why I was wondering where the car picks up is because after my TCM/PCM tune, I'm seeing very little to no improvement in 60' over stock. According to the dyno, I picked up a considerable amount of torque after getting tuned for E50, but to me it isn't reflected in the 60'. Looking at the logs, it looks like TM is seriously killing the power down low.

If your TCM has already been tuned and it is still only getting 1.6 short times dead-hooking on drag radials with over 600 rw torque, then it sounds like the TCM tune needs some more work if your goal is to use all of the power that you've paid for. Who tuned it?

[radz28]

Originally Posted by DangerZL1

How do you get around this problem in a modded 20/21 where the TCM is not tunable?

For now - you don't - really...

It is my understanding there are limitations after a certain point (what that point is, I don't know). From what I can tell, it was an old way to make the 8-speeds shift a little better, before the TCM was "unlockable". It's kinda' "raping" a spark table, and if adjusted too much, you'll lose your TM-protection between shifts. I can tell you it's done something, but couldn't tell you if it is worth it, and if it's a detriment or not.

There's not really anything, yet, that can be done. HPTuners says it will never support this new Bosch unit, which seems a little hard to believe, since it's being run in many Chevy models, but there's no reason to not believe their statements, so... Maybe EFI Live or something?...

[radz28]

Originally Posted by big dave

Thanks for the replies. The reason why I was wondering where the car picks up is because after my TCM/PCM tune, I'm seeing very little to no improvement in 60' over stock. According to the dyno, I picked up a considerable amount of torque after getting tuned for E50, but to me it isn't reflected in the 60'. Looking at the logs, it looks like TM is seriously killing the power down low.

Can you see if the throttle is still not opening all the way, or the commanded spark is still there? There are channels you can log to see what logic is being applied that could be intervening during these points. There are short-term and long-term logic that can be applied around shifts that I believe can control torque.

Things I have learned to look at include (and are not necessarily limited to): DD, VTT, and VVE. Some knowledgeable people say to only tune VVE in areas where it is necessary, and run everything else stock, and if you get your commanded spark and throttle is not limiting, then there's not much else pulling power back. Others insist on tuning the entire VVE because (on autos'), so much is dependent on torque calculations for shifting, so it is imperative get VVE right to make sure the tranny is applying enough pressure to the clutches and such. When you get into changing VVE, though, you change torque, which means you have to change VTT and probably DD. If you've changed your timing, you might have to get into VTT and DD because timing affects torque. It is a very complicated balance to which the experts and a select few (we'll call them tinker'ers - no disrespect, because I've learned from reading their posts) tinker'ers seem to have the tools or just get it.

Some of the protections for the tranny are there to protect the rest of the powertrain though. I haven't noticed many people breaking diffs (axles and maybe driveshafts more so, but not too many of these either), but it isn't only about the powertrain, if I understand correctly. I believe this torque system allows other controllers in the car make it behave as well as it does around a track and in corners. It seems to me this torque is a language these controllers can all speak and understand and that enables the powertrain to efficiently put all the power to the pavement that the chassis has the ability to process. So - maybe the limitations you might be feeling/seeing are there for the balance of power, protection, and safety, not just for you, but the car. You probably have come to that conclusion, but for me - I'm finding it's easy to get carried away and make the car behave less friendly than it was stock, and it's just not as fun sometimes.

All opinions only.

[big dave]

Originally Posted by radz28

Can you see if the throttle is still not opening all the way, or the commanded spark is still there? There are channels you can log to see what logic is being applied that could be intervening during these points. There are short-term and long-term logic that can be applied around shifts that I believe can control torque.

Once again, I really do appreciate the reply and knowledge you guys are passing on. According to my logs, the throttle is opening up to 84%. But I don't know if this is the norm since I'm seeing the same percentage with the stock tune in as well. I'm curious if with the TCM tune the transmission should shift more firm. I actually prefer how it shifts with the stock tune in race mode, it seems to be a firmer more positive shift. The last thing I want to do is burn up the trans.

[radz28]

I'm not expert, and there are plenty of other Members here who have more knowledge than I do, but I try to be helpful.

Perhaps, as you might know, some PIDs don't report 100% opening. I believe 84% can be full throttle, so I'd be inclined to say you're probably getting WOT. You can darn right make it firm'er and faster with your year. Unless it's changed, you'd have to send your TCM to HPTuners (or buy one of theirs) to unlock it, and I believe it takes 4-more credits to actually tune the TCM once it's in the car. You would then have unrestricted access to everything HPTuners has made available up to now. There are guys that have only tuned the TCM and gained several tenths in the 1320, with no more added power mods', and otherwise stock car (probably driver mod', too, but the point is there are gains); it seems perhaps you already have a driver mod', ha! Others have found a couple smaller things you can change without getting into the TCM, but it involves lowering the stock protection a little, and you already understand the risk.

I think if you find someone (ask Jannetty) here for some thoughts, that you'll find some of the information you're looking for. There are others I've noticed, too, but I don't want to offer them out-right when Jannetty is plenty capable/competent and is also a Sponsor for our Community. You're already tuned, so maybe do a little research on minimum spark timing and see what you find... Ask JRE what he thinks he can offer you, if you haven't already.