TCM Tuning
Instructor
Joined: Mar 2018
Posts: 107
Likes: 34
Success! It was damp and cool with traffic so I could not do much "testing".
I did a 1st gear test rolling on the throttle until 7200k and shifting but it worked.
I can hit 40mph in first vs 35mph now... lol! (Little pdr clip linked below.)
RPM Test
I did a 1st gear test rolling on the throttle until 7200k and shifting but it worked.
I can hit 40mph in first vs 35mph now... lol! (Little pdr clip linked below.)
RPM Test
Instructor
Joined: Nov 2011
Posts: 127
Likes: 62
From: South FL (Fort Lauderdale)
Burning Brakes
Joined: Sep 2019
Posts: 926
Likes: 611
From: Navarre, Florida
TCU restrictions or lack of tuning has single-handedly stopped me from taking the C8 seriously as a potential vehicle for me in the future. This is all good news but, I would certainly prefer direct tuning of the TCU or even a complete replacement of the module itself for the sake of tuning.
Melting Slicks
Joined: Aug 2022
Posts: 2,784
Likes: 3,566
You can tune the thing until the cows come home but what it needs is a new 1:1 4th gear, the old 0.85:1 4th can be the new 5th, etc. These are OHV truck engines, not sure revs are really the answer. Keep in mind there are also tuners that don't like to mess with increasing the redline even in M mode because they are trying to protect the transmission. I imagine they have encountered some drivability weirdness when they tried it. I'm all about the cammed cars revving to 7000 but nothing but a new gear set is going to make these cars even remotely 'fast'.
Instructor
Joined: Nov 2011
Posts: 127
Likes: 62
From: South FL (Fort Lauderdale)
You can tune the thing until the cows come home but what it needs is a new 1:1 4th gear, the old 0.85:1 4th can be the new 5th, etc. These are OHV truck engines, not sure revs are really the answer. Keep in mind there are also tuners that don't like to mess with increasing the redline even in M mode because they are trying to protect the transmission. I imagine they have encountered some drivability weirdness when they tried it. I'm all about the cammed cars revving to 7000 but nothing but a new gear set is going to make these cars even remotely 'fast'.
Instructor
Joined: Mar 2018
Posts: 107
Likes: 34
It will be but its absolutely useless without being able to tune the tcm. The real question to me about all this is how can the rest of the car be designed so well but the geniuses who designed the gearing ratios never seemed to understand the engines power curve for them to be utilized effectively? 4th to 6th are horrible for it's power and it even seems the z06 suffers considering it's Ring time around the track.
Burning Brakes
Joined: Sep 2019
Posts: 926
Likes: 611
From: Navarre, Florida
Perhaps a standalone option could be explored for just the TCU?
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Instructor
Joined: Nov 2011
Posts: 127
Likes: 62
From: South FL (Fort Lauderdale)
I think a stand alone could definitely and easily be made and programmed to handle the DCT, my concern would be how would the canbus linking it to ALL the other computer systems of the car handle it?
It seem to me the best options out there so far to help mitigate this issue quite a bit is just to TT your motor or bolt in a positive displacement blower. They fatten the torque curve of the motor significantly and independently of the revs, making the low ratios of 4th and 5th not 'as much' of an issue.
Seeing that the engineering team at GM had drawn up the design for the TT ZR1 first and worked backwards with the intro of the stingrays then Z06 before it's release, I'm pretty sure the ratios mate up with the 1000HP Turbo ZR1 motor nicely..
It seem to me the best options out there so far to help mitigate this issue quite a bit is just to TT your motor or bolt in a positive displacement blower. They fatten the torque curve of the motor significantly and independently of the revs, making the low ratios of 4th and 5th not 'as much' of an issue.
Seeing that the engineering team at GM had drawn up the design for the TT ZR1 first and worked backwards with the intro of the stingrays then Z06 before it's release, I'm pretty sure the ratios mate up with the 1000HP Turbo ZR1 motor nicely..
Melting Slicks
Joined: Aug 2022
Posts: 2,784
Likes: 3,566
Yep. One gear set for the full range. I'm sure the engineers argued for it but accounting shut them down. Keep in mind that this car launched with a $59,990 base MSRP. There needed to be compromises. A lot of compromises.
Instructor
Joined: Nov 2011
Posts: 127
Likes: 62
From: South FL (Fort Lauderdale)
Le Mans Master
Joined: Oct 2005
Posts: 5,046
Likes: 884
From: Tampa Florida
Pro
Joined: Sep 2000
Posts: 678
Likes: 310
From: McKinney Texas
Looks like it will be soon for real this time....
Melting Slicks
Joined: Aug 2022
Posts: 2,784
Likes: 3,566
Cautious optimism here. Wondering what a proper head and cam car can make being able to rev safely to 7000-7100? 600whp is maybe in the cards with enough airflow mods to both intake and exhaust. NA C8s will break into the mid-10s if so.
Instructor
Joined: Nov 2011
Posts: 127
Likes: 62
From: South FL (Fort Lauderdale)
Reliable redline increase has (or had) to be demonstrated first before they start building custom cams/ heads,runnners,etc around it...
Le Mans Master
Joined: Mar 2001
Posts: 8,433
Likes: 3,921
From: Omaha
2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
If it's auto shifting, it wouldn't matter. But for manual mode, you can actually get the tach to show numerical in some modes, although it's going to be hard to time a shift based on that. I'd either shift at 7K or add a separate shift light. I had a small red led shift light in the AC vent on one of my C4 ZR-1s, and it was perfect, when it lit, I didn't even think about it, I just shifted reactively. Had a 7400RPM rev limit and the shift light set at 7200, never once hit the rev limiter when relying on that light.
Instructor
Joined: Nov 2011
Posts: 127
Likes: 62
From: South FL (Fort Lauderdale)
Can the digital tach be reprogrammed to extend it's markings to 7500 and redline to 7000? Anyone THAT good?
