6L90 TCC settings stock converter

[Cuz]

2014 HSV GTS LSA with stage 4 circle D kit and stock converter. approx 750hp. These are the "better" converters compared to the truck ones.

What are everyone's thoughts on this TCC Desired Pressure and Apply Ramp tables?

I feel like they could be better for 1/4 mile and longevity, TCC line pressure is not hitting the max 109psi and I see about 80-100 rpm slip.

I think the lower torque values in the apply table up to 1500nm mean at WOT it's not giving full line pressure to lock.

Tune and a log with a WOT attached too

[hjtrbo]

You're at the limit of what it'll hold. You can increase the tcc desired pressure up to max if you want to clamp it down to 0. But do so at your own risk. And then to take away any value my commentary holds, I'll contradict that statement by stating I've not read or watched anything to date where there is a pattern of 6 bolt ZL1 6L90 converters going down like the plague that is the 3 bolt 6L80 converter.

As to whether there are any gains with this converter locked vs unlocked we'd need to throw it on a dyno to see. On the street I've done back to back runs with the same converter as you using an acceleration math parameter and have not been able to reliably come to a conclusion.

[TransGo Robert]

I don't think raising the lock-up apply pressure is going to stop it from slipping, the converter simply does not have enough clutch surface area and the wrong lining to hold that much torque. And even if you run it at max TCC solenoid pressure and it is a stock converter with the stamp steel piston designed to flex it will bow and touch the cover which will cause the converter to fail sooner than later. IMO you are simply asking the converter to do more then it can physically do.

[Cuz]

You're at the limit of what it'll hold. You can increase the tcc desired pressure up to max if you want to clamp it down to 0. But do so at your own risk. And then to take away any value my commentary holds, I'll contradict that statement by stating I've not read or watched anything to date where there is a pattern of 6 bolt ZL1 6L90 converters going down like the plague that is the 3 bolt 6L80 converter.

As to whether there are any gains with this converter locked vs unlocked we'd need to throw it on a dyno to see. On the street I've done back to back runs with the same converter as you using an acceleration math parameter and have not been able to reliably come to a conclusion.

Thanks for the reply. So to flip the question, by not clamping it down to 0 and letting it slip a little....is an issue for longevity?

[Cuz]

I don't think raising the lock-up apply pressure is going to stop it from slipping, the converter simply does not have enough clutch surface area and the wrong lining to hold that much torque. And even if you run it at max TCC solenoid pressure and it is a stock converter with the stamp steel piston designed to flex it will bow and touch the cover which will cause the converter to fail sooner than later. IMO you are simply asking the converter to do more then it can physically do.

This is true for the ZL1 style 6L90 converter?

[hjtrbo]

So long as your not burning the fluid. And there's a big difference between 80rpm of slip and 5.

[TransGo Robert]

Thanks for the reply. So to flip the question, by not clamping it down to 0 and letting it slip a little....is an issue for longevity?

it all depends how much is a little slip. The factory woven carbon lining will handle up to 40 RPM of slip constantly without any issue at all, it is designed specifically to do that. Same thing for momentary slip of 60-80 RPM during shifts, no issue whatsoever. But, prolong slip above 40 will cause hot spot on the cover and prolong slip above 60 will hurt the damage. So it is all a balancing act, for the longest possible clutch life with a factory stamped steel piston and woven carbon lining 20-30 RPM of slip is the sweat spot.

[TransGo Robert]

This is true for the ZL1 style 6L90 converter?

Good question. I should have specified that this applies to all 6L series single disc OE converter. It does not apply to the ones with captive clutch. I don't know how much converter clutch apply pressure those can handle before damage can occur.

[Cuz]

it all depends how much is a little slip. The factory woven carbon lining will handle up to 40 RPM of slip constantly without any issue at all, it is designed specifically to do that. Same thing for momentary slip of 60-80 RPM during shifts, no issue whatsoever. But, prolong slip above 40 will cause hot spot on the cover and prolong slip above 60 will hurt the damage. So it is all a balancing act, for the longest possible clutch life with a factory stamped steel piston and woven carbon lining 20-30 RPM of slip is the sweat spot.

Great info. What to you think of the wot run in log i posted in relation to what you describe?

[TransGo Robert]

Great info. What to you think of the wot run in log i posted in relation to what you describe?

I don't like it, specially if this is something you do frequently. The main reason is that not all identical RPM slip generates the same amount of heat.

From factory during normal driving cruising along the computer will send between 20-40 psi to apply the clutch and keep it at the 20 RPM desired slip rate. But now will all that torque applied in order to keep it from slipping you are ramping up the pressure to roughly 100 psi and this applies to a piston with a huge surface area, so that's a lot more force there. To give you an idea how much difference it makes, the piston surface is roughly 93 square inches, so we are talking 1,260 to 3,720 pounds of force on that piston and now going up to 9,300 pounds! As you can imaging that same 20 RPM of slip will generate much more heat under so much more force. None of the components in there (piston, lining, cover) were ever designed for anything like that, I don't know how long it will take before one or all three gets damaged. All in all, if you are going to do WOT pulls and keep the lock-up apply, you really need a different converter.

Talking about the force applied to the converter clutch piston, here's something that might help illustrate why it is a problem. GM has been using ECCC converter clutch strategy since 1996, so nothing new here with the carbon woven lining and the ability to have 20-40 RPM of slip constantly without it causing any issue, but on the 6L series they added a new twist. To help provide the computer with finer precise control of the slip rate they started using a tapered piston instead of a flat one. The way it works is that at first, only the outside edge of the lining is applying. As the computer increases the apply pressure to reduce the slip, the piston flattens out and now the whole surface comes in contact with the cover. In the pictures below, the image on the left is before force is applied to the piston, and the picture on the right is once pressure is applied flattening out the piston against the cover.
Tapered.png

Notice how little the gap is between the piston and the converter cover in the image on the right with some force applied to the piston flattening it out? Now imagine what happens when someone goes in an change the tune to try and make the clutch have zero slip even under heavy load. The piston does not stop flexing, with enough pressure (which it was never design to have in the first place), the piston ends up bowing enough to touch the cover. Once that happens it does not take very long for the whole thing to self destruct. With a good quality aftermarket converter you will have a new billet cover AND a new flat billet lock-up piston that can handle the extra pressure and a lining that provides a good seal and easily lock instead of the factory woven type material that can never seal completely, so going to zero slip, even under heavy load is no longer a problem.

[hjtrbo]

Here is a VF2 HSV Clubsport 3rd gear rip 550rwkw. Pulling it down mid WOT for testing. Looks a lot better than yours.

[Cuz]

I don't like it, specially if this is something you do frequently. The main reason is that not all identical RPM slip generates the same amount of heat.

From factory during normal driving cruising along the computer will send between 20-40 psi to apply the clutch and keep it at the 20 RPM desired slip rate. But now will all that torque applied in order to keep it from slipping you are ramping up the pressure to roughly 100 psi and this applies to a piston with a huge surface area, so that's a lot more force there. To give you an idea how much difference it makes, the piston surface is roughly 93 square inches, so we are talking 1,260 to 3,720 pounds of force on that piston and now going up to 9,300 pounds! As you can imaging that same 20 RPM of slip will generate much more heat under so much more force. None of the components in there (piston, lining, cover) were ever designed for anything like that, I don't know how long it will take before one or all three gets damaged. All in all, if you are going to do WOT pulls and keep the lock-up apply, you really need a different converter.

Talking about the force applied to the converter clutch piston, here's something that might help illustrate why it is a problem. GM has been using ECCC converter clutch strategy since 1996, so nothing new here with the carbon woven lining and the ability to have 20-40 RPM of slip constantly without it causing any issue, but on the 6L series they added a new twist. To help provide the computer with finer precise control of the slip rate they started using a tapered piston instead of a flat one. The way it works is that at first, only the outside edge of the lining is applying. As the computer increases the apply pressure to reduce the slip, the piston flattens out and now the whole surface comes in contact with the cover. In the pictures below, the image on the left is before force is applied to the piston, and the picture on the right is once pressure is applied flattening out the piston against the cover.
Tapered.png

Notice how little the gap is between the piston and the converter cover in the image on the right with some force applied to the piston flattening it out? Now imagine what happens when someone goes in an change the tune to try and make the clutch have zero slip even under heavy load. The piston does not stop flexing, with enough pressure (which it was never design to have in the first place), the piston ends up bowing enough to touch the cover. Once that happens it does not take very long for the whole thing to self destruct. With a good quality aftermarket converter you will have a new billet cover AND a new flat billet lock-up piston that can handle the extra pressure and a lining that provides a good seal and easily lock instead of the factory woven type material that can never seal completely, so going to zero slip, even under heavy load is no longer a problem.

This information is gold. I'm sure not only for me, but for lots of others I've searched high and low for this sort of information, so great to finally know.

Just confirming again, all that you describe is true for the captive clutch type converter hat my 6L90 has? If yes, seems I should turn off the lockup in all gear except 5 and 6 maybe.

[Cuz]

Here is a VF2 HSV Clubsport 3rd gear rip 550rwkw. Pulling it down mid WOT for testing. Looks a lot better than yours.

Yeah, that looks pretty god to me! I can see in your log that you are hitting a higher TCC Apply pressure - 758kpa vs my 622kpa. So, If I wanted to bump mine up to test, what to change in the tune? The the TCC Desired pressure, TCC Apply Table, Regulator Gain, Regulator offset?

[hjtrbo]

Referencing my log where I've marked, is where you set the apply ramp, adjust by small increments.

Reg gain and offset have no effect when reg settings switch is off.

[hjtrbo]

Notice how little the gap is between the piston and the converter cover in the image on the right with some force applied to the piston flattening it out?

The frictions give us a bit more clearance?

Now imagine what happens when someone goes in an change the tune to try and make the clutch have zero slip even under heavy load. The piston does not stop flexing, with enough pressure (which it was never design to have in the first place), the piston ends up bowing enough to touch the cover.

If they weld themselves together we'll have 0 slip and a 100% converter efficiency .

[Cuz]

Referencing my log where I've marked, is where you set the apply ramp, adjust by small increments.

Reg gain and offset have no effect when reg settings switch is off.

Nice!! The Desired Pressure table you provided looks very different to what I have, what I have I believe are the stock values (I compared mine to a Clubsport LSA tune file and they match).

You think if I matched the whole table you have I would achieve a similar apply pressure max?

[hjtrbo]

Worth a shot. You've got me scratching, I now have to ask, what drove the decision to re-build your transmission? The stock 6L90's over here are proven to run 9 seconds all day with the stock converter (unlocked). Secondly, you dropped some decent coin on that upgrade, in a $100k+ car, you left out the nice triple disc converter?

[TransGo Robert]

This information is gold. I'm sure not only for me, but for lots of others I've searched high and low for this sort of information, so great to finally know.

Just confirming again, all that you describe is true for the captive clutch type converter hat my 6L90 has? If yes, seems I should turn off the lockup in all gear except 5 and 6 maybe.

No it is different for the captive clutch setup as I mentioned before but did not explain why. First you have almost double the friction surface area so it requires less pressure to be able to maintain zero slip. The math is also different as far as the force applied because the diameter of the piston is roughly an inch smaller so much less force for a given PSI. Then you have the fact that the piston can bowmore before touching the cover since you now have the two friction lining and the steel plate in between. It is still not a good idea to rank up the pressure super high on a factory converter with captive clutch, but it is more forgiving and should not require that much pressure to achieve zero slip in the first place.

[Cuz]

Worth a shot. You've got me scratching, I now have to ask, what drove the decision to re-build your transmission? The stock 6L90's over here are proven to run 9 seconds all day with the stock converter (unlocked). Secondly, you dropped some decent coin on that upgrade, in a $100k+ car, you left out the nice triple disc converter?

Broke an intermediate shaft due to a poor tune and improper torque calculations.

I had the converter rebuilt while the box was out, but logic was the same as yours above....stock converter should be good for 9s so why upgrade.

I'm thinking more and more about whether trying to lock it up in anything other than 5 and 6 is even worth it.....any insights on whether this would or wouldn't make a difference at the track?

[TransGo Robert]

The frictions give us a bit more clearance?



If they weld themselves together we'll have 0 slip and a 100% converter efficiency .

The lining is there in the picture, it is brand new, you just have to zoom in to see it because it is only 0.020" thick.

It would be nice if all that pressure that bows the piston made it fully lock. Unfortunately if the pressure goes high enough to make the piston touch it just makes it slip more for three reasons. First the piston is now sitting against the cover in the center so the full force is no longer on the lining only. Second is that by now, it is bowed the other direction then before applying pressure causing a taper the other way. The result is that now only the ID of the lining is touching. More fluid can now pass across the small part of the lining touching as you have less area with the weaves restricting the fluid. The other big issue with that, is that just like the 4T65E that had that issue years ago, once the piston bows that far, it passes the point of no return so it does not go back to its original shape.