G8 6L80 TCC not staying locked on WOT

[Chris@MooreAutomotive]

Hi guys,
I have a 2009 G8 GT with a 404 and a Maggie 1900 blower, PATC Phoenix level 4 built trans and billet 2000rpm converter. Car makes 750whp/780tq. My issue I'm having with it is it just blows through the converter and bangs the rev limiter and doesn't shift. If I lock the converter through HP Scanner, it'll shift nice and clean. So I've been trying to get the converter to stay locked on WOT. No matter what I put in the TCC tables; normal, pattern A, and WOT, it'll command the converter to unlock on any significant throttle increase. I even have shift lock enabled. Is this something that hard coded into the G8 TCM, will in not lock below the factory 95mph in 4th on WOT?

Thank you for any input.

[realcanuk]

Post the tune and if possible a log. That will help us to help you.

[Chris@MooreAutomotive]

Ok, Here's the latest tune I was using to test with. In the log file, in the first half you'll see the TCC be commanded on and then go off when I stab the gas. Towards the end of the log I used Scanner to lock the TCC and do wot shifting runs to see if it would actually shift (and it did). So basically I need the converter to stay locked in order for this thing not to blow through this converter.

[Chris@MooreAutomotive]

Anyone? Even if you could take a look at the tune and tell me all my TCC settings should suggest that it stay lock and I'm (hopefully) not doing something wrong or over looking something. I've tried so many things and nothing's worked, at this point I can only believe that it's hard coded in the G8 trans OS.

[realcanuk]

Anyone? Even if you could take a look at the tune and tell me all my TCC settings should suggest that it stay lock and I'm (hopefully) not doing something wrong or over looking something. I've tried so many things and nothing's worked, at this point I can only believe that it's hard coded in the G8 trans OS.

Best I can do is look in detail this aft, and see if I can spot anything.

[Chris@MooreAutomotive]

I'd definitely appreciate it. I tried a write entire last night just in case the settings weren't taking, that didn't help. Mainly trying this in TUTD since there's only the main apply/release tables (no WOT tables for TUTD) and it seems to follow those tables while driving normally. I also noticed even though I have shift lock enabled, it'll still unlock the converter for 1-2 and 2-3 shifts, but 3-4, 4-5, 5-6 it stays locked during the shift. But still unlocks on any increase in throttle in all gears.

[realcanuk]

Took a brief look. Will look more later but one thing that stands out to me is that you have the TCC adapts disabled. I don't know what effect that has, but I have never noticed that done before. I would set those back to stock, and try it. It seems to drop the TCC pressure when you give gas and have that problem. Weird one for sure.

[Chris@MooreAutomotive]

They shouldn't be disabled, if anything I made the parameters for adapts to be wider and be on all the time. But yeah, TCC pressure is just commanded to 0 on acceleration

[realcanuk]

They shouldn't be disabled, if anything I made the parameters for adapts to be wider and be on all the time. But yeah, TCC pressure is just commanded to 0 on acceleration

My mistake.. you are right. I was rushed looking at it while working and read the 1200 as in the torque min field, not max. I would still put them to stock, along with the KPA just to try, only because I have never seen them changed before, and they seem to work fine stock. I still have had much time to spend looking, but I didn't see anything else that stands out. The TCC apply pressure seems really high compared to mine, but if anything that should lock it harder.

Its odd the way the TCC pressure just drops right off. I guess if it works locking it with the scanner controls, it isn't a mechanical issue.


One other thing I might try is lowering the speeds you have it set to lock at, right across the board. You have them low in 94 and 100% columns, but maybe at 75%, for example, you aren't reaching the speed set. Worth a try I think.

[Chris@MooreAutomotive]

I actually tried it with the normal and pattern A apply pressures the same as TUTD from 37% and up and it still did the same thing. So I changed it back, I also figured if it's in TUTD it shouldn't reference those tables at all anyway. Also had the adapt parameters stock when I first noticed it, that's why I changed it to be wider and adapt all the time. Thank you for looking, I'm more or less trying to verify I haven't missed anything in the tune. I really think it's hard coded in the tcm or there's a table we don't have that's controlling the unlock on accel. I found a few threads from years back about people complaining about it, but nothing outside of that.

[gmonde]

it looks like its in unlocking or slipping at 4750 ,, right at the same time its showing the gear change 3-4 shift it slips the trans (maybe in between commanded shifts) ,it also shows in the channels you are in tutd mode ,but the graph hasn't made the gear change until 6700 or so , are you shifting @ 4750 or later?

look at your turbine speed ,input speed and are the same but look at your trans slip rpm ,, it slips at the that 4750 (at the end of the log (88% throttle ) almost seams like your running thru the clutches ,, check you fluid condition

[realcanuk]

I actually tried it with the normal and pattern A apply pressures the same as TUTD from 37% and up and it still did the same thing. So I changed it back, I also figured if it's in TUTD it shouldn't reference those tables at all anyway. Also had the adapt parameters stock when I first noticed it, that's why I changed it to be wider and adapt all the time. Thank you for looking, I'm more or less trying to verify I haven't missed anything in the tune. I really think it's hard coded in the tcm or there's a table we don't have that's controlling the unlock on accel. I found a few threads from years back about people complaining about it, but nothing outside of that.

I don't think its in the ECM. Isnt that an E38... never heard of it being a problem before.

[GHuggins]

You might want to check the torque model if your having clutch holding issues... Haven't personally looked at the log, but almost sounds like your shift timing is wrong more so than tcc setup?

[Chris@MooreAutomotive]

it looks like its in unlocking or slipping at 4750 ,, right at the same time its showing the gear change 3-4 shift it slips the trans (maybe in between commanded shifts) ,it also shows in the channels you are in tutd mode ,but the graph hasn't made the gear change until 6700 or so , are you shifting @ 4750 or later?

look at your turbine speed ,input speed and are the same but look at your trans slip rpm ,, it slips at the that 4750 (at the end of the log (88% throttle ) almost seams like your running thru the clutches ,, check you fluid condition

My issue is that the converter is unlocking any time I accelerate. Where are you looking in the log? If you're looking towards the end were I made the 3-4-5 run, that was a test with the converter locked through HP Scanner, and it shifted fine (clutches are holding). I'm talking about where you can see I'm cruising at a steady speed with the TCM locking the converter in TUTD, and I go to accelerate and the TCM unlocks the converter. But all my apply tables say it should stay locked. The trans is newly built, fluid is new as well.

[Chris@MooreAutomotive]

You might want to check the torque model if your having clutch holding issues... Haven't personally looked at the log, but almost sounds like your shift timing is wrong more so than tcc setup?

I'm not having clutch holding issues, my issue is that the converter is being commanded to unlock whenever I accelerate from a cruise. Even though all the apply tables say it should stay locked. I need the converter to stay locked because this car makes so much torque it's blowing through the converter (PATC billet 2000 stall). But if I lock the converter, it shifts fine because it's not hitting the rev limiter before it sees the correct shift mph.

[Chris@MooreAutomotive]

I don't think its in the ECM. Isnt that an E38... never heard of it being a problem before.

C_Nieswanger_2011_CTS-V_416_BTR3_850_Flex_TCC_Example.hpl

Here's a log I just did of a CTS-V I was tuning. You can see in TUTD it'll lock the converter (as per the tables) and on acceleration, it won't unlock it, in fact TCC commanded pressure goes up! The only difference in the TCC portion of the tunes is that the CTS-V has numbers in the table for "Apply Ramp 4WD Low" but I wouldn't think that table would even be used. Doesn't make any sense.

[realcanuk]

Before my current setup I was running an PD blower making simiar power to what you are here. I have a Circle D 2600 triple and never had this issue. I only locked in 5th and 6th but could accelerate without it unlocking no problem.

Maybe you should try just not locking it through 4th. Ran great that way for me.

[realcanuk]

You might want to check the torque model if your having clutch holding issues... Haven't personally looked at the log, but almost sounds like your shift timing is wrong more so than tcc setup?

I didn't want to get into that because I am not sure it would cause this issue, but I noticed the torque model not touched, and also the torque management turned off. Not the way I would personally do it. Also noticed some strange scaling with the stoich numbers. That might effect the reported torque even more, and be causing some shift issues.

[Chris@MooreAutomotive]

I can't run it unlocked because it blows through the converter and bangs the rev limiter before wheel speed is at the shift point, I tried setting the shift speed way down and that still didn't help. It just goes through the rev range too fast and this trans can't shift correctly when something (converter or tires) is slipping that bad.

I tried changing the torque model numbers and it didn't affect it, I was told that'll only change shift pressures. The stoich numbers are like that because I was working with the guy on 6l80tuning.com and he said the maf scaling had to be higher to get reported torque up higher (was only around 500 at wot on the first tune I did), so because of the fuel system and intake/maf setup, and the ceiling on the injector scaling, that's how the fuel had to be tuned in to get reported torque back up and not be extremely rich. I have the old tune with has more normal numbers in all those tables and it still does the same thing.

[realcanuk]

I can't run it unlocked because it blows through the converter and bangs the rev limiter before wheel speed is at the shift point, I tried setting the shift speed way down and that still didn't help. It just goes through the rev range too fast and this trans can't shift correctly when something (converter or tires) is slipping that bad.

I tried changing the torque model numbers and it didn't affect it, I was told that'll only change shift pressures. The stoich numbers are like that because I was working with the guy on 6l80tuning.com and he said the maf scaling had to be higher to get reported torque up higher (was only around 500 at wot on the first tune I did), so because of the fuel system and intake/maf setup, and the ceiling on the injector scaling, that's how the fuel had to be tuned in to get reported torque back up and not be extremely rich. I have the old tune with has more normal numbers in all those tables and it still does the same thing.

There is no reason it should blow through the converter, locked or not, unless maybe the converter is bad. Like I said, I ran a pd blower with 780rwhp, and now a centri with over 1000, and it shifts fine locked or unlocked. One other thing is to make sure that traction control, assuming the car has it, is off. If it is active at the time of a shift, it will cause issues.

Personally, I would start from scratch. Double stoich, halve IFR and IVT terms, and tune from there. Adjust the torque reporting with the airmass tables and start with some base shift and lockup numbers from bluecats spreadsheet. Fine tune from there. In my opinion, there is too much going on to rule out the tune completely. If redoing it (what I would call properly) doesn't fix the issue, then I would think its mechanical.

I am not trying to tell you how to tune, but I can tell you doing it that way just works without issues. It is definitely not something hard coded. Tons of cars running around with that ECU without issues like this. These transmissions are tricky and it doesn't take much to cause issues.