8L45, ATS vs Camaro

Curious find. I'm comparing the stock tunes on two 2016 LTG alphas, an ATS and a Camaro. There are a few minor differences overall but one thing that stands out as pretty dramatically different is the TCC lockup speeds. In the ATS in 2nd gear and higher, the TCC locks up at a much higher speed than the Camaro. At full throttle the ATS basically does not lock up. In the Camaro however, the TCC locks up almost instantly across all throttle values including full throttle.

Why would GM program such different characteristics across the same architecture? and more importantly, does anyone have opinions on the performance impact of the two different strategies under full throttle?

Picture below shows the ATS on top and the Camaro below.
Attachment 69868

Attachment 69869

We have always added lockup in second gear for years to get .3-.4 tenths off the quarter mile and 2-5 mph more. The reason triple disk converters came out with say a 700r4 or 4l60e had it on a toggle switch and threw it at top of first so shifted to second and locked up instantly. Think grand national guys started it first for big gains at the track. It is much harder on the clutch obviously so why triple disk came out to hold the power. Before doing it I would see if the ats has a different part number for the torque converter or not as can kill a lockup clutch if not designed to do it especially if making more power. Camaro more geared to performance so makes sense it has it and an ats doesn't. I would be concerned the ats converter might be different. I build transmissions for a living so know this kind of stuff well.

Thanks @lt1z350, good info. I did a quick search on all the normal online GM parts catalogs and can't find converter part numbers for the 2016s, but I'll keep looking.

lt1z350 - do you know if zeros in the TCC tables means "never apply" or "always apply"? Take a look at this screenshot as an example
Attachment 70164

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Originally Posted by dekes1

lt1z350 - do you know if zeros in the TCC tables means "never apply" or "always apply"? Take a look at this screenshot as an example
Attachment 70164

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I would think that it would be always apply, but I'm not certain... If that's what you were trying to do, I would just set it to 1 myself... In your first row, it will never apply because that speed will never be reached... However, I would think that that what you have there maybe cause you problems when coming to a stop, you may experience a shudder, or stalling if coming to a stop and the the converter is locked and say you're in still in second gear because the stock 2>1 down shift is at 4mph @ 0% tps... I believe your apply numbers need to be higher than your release numbers to not cause you issues. But you aren't showing the release numbers, so I'm just guessing at what you're doing here...

Also, the TCC doesn't lock instantly... For instance in the stock 16 2.0 camaro tune, at WOT the TCC is commanded to start locking right after the 1-2 shift completes, and if you log the TCC pressure, and slip, you can see that it doesn't have full pressure and stops slipping untill the middle of third gear (at about 58 mph for me)... So it starts the build pressure to lock at 36mph (in my log), and isn't "fully" locked until 58mph, or time wise, at least in this instance, it takes 4.224 seconds from the time it's commanded to lock, to the time it actually "locks" (at WOT, haven't checked it to see how quick it can lock at part throttle driving)...

At current time there is no adjustability for the TCC max pressure, or apply ramp, or desired slip like the old A6 TCM's had, so we're kind of stuck with that we got... I asked when/if additional a8 tables would/could be added and the response I got from Bill @ HPT was:

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"Whatever is in there is what we've been able to find. You can't compare a T43 tcm to a T87, its like comparing apples to oranges."

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I can't imagine all the stuff that the 6 speed TCM isn't in the 8 speed... I think it's just a matter of them finding it and implementing it.

Believe it or not, that table above with all the zeroes is not the result of me playing. It's the actual factory table for lockup when in TUTD mode. It surprised me when I saw it and even more surprising when I compare it to the same table in the Camaro stock tune.

-RacnJsn95 have you experimented with Base Shift Pressure with TCC On to see if it affects the ramp in or slip values?
Also, in both the ATS and the Camaro there are those Upshift pressure tables that are all zeroed out. I'm going to run some tests with adding to those tables.

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Originally Posted by dekes1

Believe it or not, that table above with all the zeroes is not the result of me playing. It's the actual factory table for lockup when in TUTD mode. It surprised me when I saw it and even more surprising when I compare it to the same table in the Camaro stock tune.

-RacnJsn95 have you experimented with Base Shift Pressure with TCC On to see if it affects the ramp in or slip values?
Also, in both the ATS and the Camaro there are those Upshift pressure tables that are all zeroed out. I'm going to run some tests with adding to those tables.

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I see.

Changing the base shift pressure for tcc on or off does not seem to effect the TCC locking/slip... Pretty sure the tables we need are not there yet. Those Upshift pressure X/y/z tables you are talking about? They are offsets for different modes (like sport/touring, etc)... They will just add or subtract to the base pressure tables.

I'm new to the automatic transmission tuning. Just curious what would a transmission shifting speed table look like to shift to each gear the quickest? A friend of mine has a very quick shifting tune setup from zzp for his 2016 ats 8 speed auto. I have a '17 8 speed auto and realized it shifts much slower than my friends but I'm all stock.

Anyone?

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Originally Posted by Ryansalazan

Anyone?

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It's tough to just show a set of values and state "this is what you need". The reality is that it's a trial and error process. For example, i found that if i try to go overly aggressive with shift timings, the trans actually gets confused and will lurch/miss shifts and complain. There are also some interrelated tables like "shift intertia" that play into the overall shift feel.

Just as a baseline, my experience has shown that you can set the fastest shift times in the table to a value starting at about 200ms and gradually decrease from there in 5ms steps. Run some tests to get the feel and consistency you want. Then smooth the table for the other cells in the table. I have not had much success going below 125ms.

Shift intertia works good around 9, but some folks go as aggressive as 12. Once again you need to experiment and adjust as necessary.

Once you start digging into the tuning, send me a PM and i can give you my unprofessional but experienced opinion on your settings.

Edit: one other consideration - i've spent about as much time testing the TCC lockup settings as i have testing the shift times. i find hat the TCC lockup has a huge impact to the crispness and impact of the shift. it's another area that will need some of your focus as you tune.

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Originally Posted by dekes1

It's tough to just show a set of values and state "this is what you need". The reality is that it's a trial and error process. For example, i found that if i try to go overly aggressive with shift timings, the trans actually gets confused and will lurch/miss shifts and complain. There are also some interrelated tables like "shift intertia" that play into the overall shift feel.

Just as a baseline, my experience has shown that you can set the fastest shift times in the table to a value starting at about 200ms and gradually decrease from there in 5ms steps. Run some tests to get the feel and consistency you want. Then smooth the table for the other cells in the table. I have not had much success going below 125ms.

Shift intertia works good around 9, but some folks go as aggressive as 12. Once again you need to experiment and adjust as necessary.

Once you start digging into the tuning, send me a PM and i can give you my unprofessional but experienced opinion on your settings.

Edit: one other consideration - i've spent about as much time testing the TCC lockup settings as i have testing the shift times. i find hat the TCC lockup has a huge impact to the crispness and impact of the shift. it's another area that will need some of your focus as you tune.

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This is awesome thanks man for the input. In a couple of weeks I'm going to be sending off the tcm to hptuners to get it unlocked. I'll add you as a friend on the Ats forums

Yeah, probably can't get it to shift faster than .125, and even at that, I can only get my 3-4 shift to do that. The other gears are in the .150-.200 range, but I was still experimenting with raising the max pressure.

I feel like even if it would shift faster than .125, we need more tables, specifically the off-going/on-going clutch tables to really get the timing right for a quicker shift.

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Originally Posted by RacnJsn95

Yeah, probably can't get it to shift faster than .125, and even at that, I can only get my 3-4 shift to do that. The other gears are in the .150-.200 range, but I was still experimenting with raising the max pressure.

I feel like even if it would shift faster than .125, we need more tables, specifically the off-going/on-going clutch tables to really get the timing right for a quicker shift.

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You think commanding the transmission to shift this quick would be bad for transmission health? Just curious over longer term effects. Also, does this faster shifting help with the shift pedals behind the steering wheel react a little quicker as well?

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Originally Posted by Ryansalazan

You think commanding the transmission to shift this quick would be bad for transmission health? Just curious over longer term effects. Also, does this faster shifting help with the shift pedals behind the steering wheel react a little quicker as well?

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I'm no transmission expert, but I've always heard there is two things that will kill a transmission. Heat, and Slipping.

When stock at WOT, in my logs I can see the trans was slipping between shifts. Not much, and I assume it's probably done on purpose for "comfort" as most people won't rod these cars and probably dont want a hard shift. You can check for slip by logging the TIME OF LATEST SHIFT and comparing it to your commanded shift times in the tune. I don't know how ACCURATE the PID is, as it always seems to log in 0.025 second increments, but it can't be that far off. At the track with the stock trans tune, I was seeing about .100 to .150 of this "slip" in some gears, not all. I don't have my laptop on my, so I can't look to see how many rpms that equates to, but you get the idea. If your time of latest shift doesn't match up with your commanded shift times at WOT, odds are there is some slip, and you either need to increase the shift pressure, or decrease the shift time. I usually only change the shift times at WOT in .025 increments anyway. You'll find that you will quickly find the limits of how fast the trans can shift with the limited tables available, if you try to command the shift too fast, you will know, and you will crap your pants thinking the transmission just fell out the back of the car, but it's probably still there, back the shift time down to a safer number and slowly creep up on it. You will find that some gears can/will shift quicker than others, this seems normal. Each gear seems to have it's own limit, which is probably both a mechanical limit, but also still limited by the lack of available tables to adjust. You will also find that sometimes some gears will shift quicker than commanded. Not sure why, and not sure if it's bad, but it's obviously not slipping. Usually when this happens to me, it's only shifting 0.025 quicker than commanded, and only in certain gears. Even though the trans is computer controlled, it's still a mechanical device that can only do what it can do regardless of what the computer tells it.

Adjusting the tune won't make your hands work any quicker when trying to use the paddle shifters, but it will still shift quicker. I don't advise using the paddle shifters personally unless you're on a winding road or road course wanting to have some fun. The computer will always upshift faster than you think you can.

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Originally Posted by RacnJsn95

I'm no transmission expert, but I've always heard there is two things that will kill a transmission. Heat, and Slipping.

When stock at WOT, in my logs I can see the trans was slipping between shifts. Not much, and I assume it's probably done on purpose for "comfort" as most people won't rod these cars and probably dont want a hard shift. You can check for slip by logging the TIME OF LATEST SHIFT and comparing it to your commanded shift times in the tune. I don't know how ACCURATE the PID is, as it always seems to log in 0.025 second increments, but it can't be that far off. At the track with the stock trans tune, I was seeing about .100 to .150 of this "slip" in some gears, not all. I don't have my laptop on my, so I can't look to see how many rpms that equates to, but you get the idea. If your time of latest shift doesn't match up with your commanded shift times at WOT, odds are there is some slip, and you either need to increase the shift pressure, or decrease the shift time. I usually only change the shift times at WOT in .025 increments anyway. You'll find that you will quickly find the limits of how fast the trans can shift with the limited tables available, if you try to command the shift too fast, you will know, and you will crap your pants thinking the transmission just fell out the back of the car, but it's probably still there, back the shift time down to a safer number and slowly creep up on it. You will find that some gears can/will shift quicker than others, this seems normal. Each gear seems to have it's own limit, which is probably both a mechanical limit, but also still limited by the lack of available tables to adjust. You will also find that sometimes some gears will shift quicker than commanded. Not sure why, and not sure if it's bad, but it's obviously not slipping. Usually when this happens to me, it's only shifting 0.025 quicker than commanded, and only in certain gears. Even though the trans is computer controlled, it's still a mechanical device that can only do what it can do regardless of what the computer tells it.

Adjusting the tune won't make your hands work any quicker when trying to use the paddle shifters, but it will still shift quicker. I don't advise using the paddle shifters personally unless you're on a winding road or road course wanting to have some fun. The computer will always upshift faster than you think you can.

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Very well said coming from someone that builds transmissions for a living.

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Originally Posted by RacnJsn95

if you try to command the shift too fast, you will know, and you will crap your pants thinking the transmission just fell out the back of the car, but it's probably still there,

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HA! I remember the first time this happened to me. I tried an overly aggressive .75ms commanded shift. On a hard run up through the gears, it tried to shift to 3rd and it just made a loud clunk, slammed into front end dive, skipped a gear, and ended in 5th. I was absolutely certain i left a trail of parts on the road. Even the dash display was still showing 2nd gear even though i was in 5th. Thankfully after i cleaned up the soiled underwear, the trans was perfectly fine.

I prefer to adjust the shift pressures along with the shift time. But if I had to adjust only one of those parameters, it would the the shift pressure.

I have the 9 speed tranny in my 18' Regal and it sucks shit in manual shift at WOT. Practically have to go from 1st gear and tap twice to go right into 3rd, then again twice to go into 5th. The gear ratios are too close from 1st to 6th.