Beginner G8 GT trans tuning

[Allmachtige]

So I've been thinking and is it really necessary to increase the upshift pressures for 1-2,2-3, and 3-4?

If I've already increased the Master Shift Pressure table for D1 through D6, what's the point in increasing the pressure for specific gears?

I rather than trash the trans, but still get the firm shifts I get at WOT.

Thoughts?

[bluessv]

It wouldn't hurt bumping them up slightly as from what I've read on these forums, GM likes to run low pressures. So I'm assuming that leaves room to move, especially if you're decreasing the shift times to almost half of what is set in the stock tune.

[bluessv]

By the way....

I see the Pontiac G8 runs a tune for the 6L80 which sets the shift times using the addition of numerous tables to get a final "Desired Shift Time". These tables include the Base Desired Shift Time, the Shift Time Inertia Adder and the Shift Time Torque Adder. It's pretty simply really, you just add the times applicable in each table and you get your total shift time that the TCM will constantly monitor and "aim" for.

I see that some of the Corvette and Camaro tunes have the "Base Desired Shift Time" and the "Shift Time Inertia Adder" tables zeroed out with all the shift data for the TCM to use being stored in the "Shift Time Torque Adder" table. Certainly makes sense and is a lot easier to follow. Would make sense too that it's easier for the TCM to monitor and calculate and therefore less likely to get confused??

Given this, has anyone out there tried using this shift time theory in the G8 where all the shift time reference tables are zeroed out except the "Shift Time Torque Adder" table?

[BMBSALES]

I've been looking at everyone's posts and tunes (thank-you by the way for those who pm'd me theirs when i couldn't find them posted), and i had a couple of thoughts/questions...if anyone had any info.

i too have upped the 2-3 adapts to 200, and i immediately noticed it helps, but i also noticed what i would best describe as a spooling up effect in that gear, meaning that when you let off the throttle in 3rd gear, it seems to now stay spooled up a bit, and almost feel like throttle is hung a bit. has anyone else felt anything like this?

for those of you who used the z-pressure pattern...am i incorrect in saying that this is the pattern the stock setup uses for overtemp? and are you worried that if it goes into an overtemp, the pressures are now going to be pretty high?

has anyone logged the trans gear selection to see what is actually occuring when you are let's say doing 55, and romp on it. my tune brings that down to 3rd gear, so we are talking 6th to 3rd. my question is, is this trans using a 6-4 skip then 4-3, or is it a 6-5 shift then a 5-3 skip? just curious if anyone looked at this, as i'm trying to work out that delay/clunk with pressures and times.

last one, i'm sorry...i am told that the reason for the discrete shift torque is not only to stabilize the shifts, but in fact it will stabilize the shifts you choose ACROSS ALL THE PATTERNS...x,y,z...special or normal.

[Allmachtige]

has anyone logged the trans gear selection to see what is actually occuring when you are let's say doing 55, and romp on it. my tune brings that down to 3rd gear, so we are talking 6th to 3rd. my question is, is this trans using a 6-4 skip then 4-3, or is it a 6-5 shift then a 5-3 skip? just curious if anyone looked at this, as i'm trying to work out that delay/clunk with pressures and times.

I'll take a look at this in more detail from now on. Never really paid attention, but I noticed that setting the Power Downshift times to .2300 helped eliminate some of that lag you're talking about.

[bluessv]

BMBSALES,

The "Discrete Shift Torque" is used to stablise the learning for a set shift which will ultimately give a better shift feel (arguable). As far as I'm aware, if the Discrete Shift Torque is "Enabled" on a specific shift then it applies to all pressure patterns.

BUMP BUMP BUMP....on the question I threw out before about people experimenting with their G8 tunes with running zeroed tables for the upshifts except in the Shift Torque Adder table such as used in the Corvette and Camaro.

[Allmachtige]

It wouldn't hurt bumping them up slightly as from what I've read on these forums, GM likes to run low pressures. So I'm assuming that leaves room to move, especially if you're decreasing the shift times to almost half of what is set in the stock tune.

What are the beginner recommendations?

I'm using a combination of pressures from a few members here.

[bluessv]

Allmachtige,

Based on the tune you posted on page 2 of this thread, I'd leave increase your upshift pressure slightly on the last cells for your pressure pattern "X" just to compensate for the increase in torque left in the shift based on your TM settings.

I'd be increasing your upshift pressures on your pattern "Y" by up to 20psi across the board as this pressure pattern is being used for "Special" mode where you've not only got increased torque but you've also lowered the shift times. I'd be only using a 20psi increase at the end cells though. But don't bother increasing the pressures on the 5-6 shift for either.

[Allmachtige]

Tell me what you think of this latest tune.

[bluessv]

Allmachtige,

I like it! I think that's getting very close to an ideal tune with a great mix between easy city driving and some nice shifting when you tromp on the gas!

The only main difference I'd be doing is "Enabling" the Discrete shift Torque as I believe it shifts better with it "Enabled". The shift pressures are set a certain way with the intention that it's "Enabled" but you've made adjustments to the pressures anyway.

But don't worry too much....there's plenty of guys on here that swear the Discrete Shift Torque is a negative so I guess it's just a matter of opinion.

Great tune!

[Allmachtige]

I actually feel the 4->5 and 6->5 shift more than anything when just taking it easy around town....er, I think.

I'll double check on the way to/from work tomorrow. I just feel these shift a little more than I remember, but I may be getting used to how this car feels.

[bluessv]

Well you do have the TM settings applied to the 4-5 shift so I would expect that. Not sure about the 6-5 though....perhaps just give it a few days for the TCM to learn a little more.

[Sneakyws6]

Shane Has Made Lots Of Progress On Leaving The Cold Multiplier Table Stock And Using The Adder Modifier Tables To Tailor The Shifts.

When I Get Home I Can Post Up My Current Tune, Right Now It Is Slightly Firmer Than Stock Around Town Then When Wot It Shifts Very Firm Like It Should.

I Have Also Changed How The Sport Mode And Manual Mode Apply The Clutches As Well In Mine So They Apply Firm Like Auto Mode Under Wot.

[icicleboy]

I Have Also Changed How The Sport Mode And Manual Mode Apply The Clutches As Well In Mine So They Apply Firm Like Auto Mode Under Wot.

Is this using the initial/final parameters? can someone explain how this works? Does the initial+ final value need to equal 1.0? going which way with the values does what to the shift feel? Does the x axis of 0 - 9 reference engine torque?

TIA!

[Allmachtige]

Well you do have the TM settings applied to the 4-5 shift so I would expect that.

Good point.

I'm using a lot of Shane's data and overlooked that. I'll probably set 4-5 to full TM because I'm never going to be going fast enough at WOT for the 4-5 shift to happen.

[04blackgmc]

Good point.

I'm using a lot of Shane's data and overlooked that. I'll probably set 4-5 to full TM because I'm never going to be going fast enough at WOT for the 4-5 shift to happen.

yea i still have the adder modifier tables affecting the 4-5...

im been making tiny changes here and there from my tune i went went 12.99and 13.02.

brought the oncoming volume back to stock and brought max adapt back all to 200 instead of 215...

[04blackgmc]

one thing i guys should log on the scanner is time of latest of latest shift(u will have to connect to the car in able to get the table)
for example my 12.9 pass
1-2 .300
2-3 .225
3-4 .175

[BMBSALES]

One thing that would really help this trans, considering all the skip shifts, is if there were torque manage DOWNSHIFT settings like the shift torque factors, adders & modifiers.

the way it sits, it's pretty simple to reduce just the right amount of torque with the beta, and then quicken them up with time and/or pressure. we all know there are about a million ways it can be done, no one more correct than the other.

BUT, the downshifts, which in my opinion for a daily driver, are just as important, there's really not much you can do. the more you quicken them or add pressure, it mostly effects the lower torque areas, because t/m is pulling so much timing and pedal, that really if you try to go to far, you just end up going slower. not to mention that t/m leaves it in where you want it least...light throttle, so you end up with harsh downshifts until you throttle it, and t/m softens the hell out of it.

we usually tackle that problem by raising wot downshift points a few mph, but that makes it a bear when it kicks down....at 55mph you're talking about a 6-2 skip...and in my C6 you have to hold the hell on.

what do you say BILL or CHRIS, is there any power downshift t/m tables lurking around in there for us?

[Allmachtige]

yea i still have the adder modifier tables affecting the 4-5...

im been making tiny changes here and there from my tune i went went 12.99and 13.02.

brought the oncoming volume back to stock and brought max adapt back all to 200 instead of 215...

I set Tip-In and Shift Ctrl Termination back to stock and downshifts feel softer...or its all in my head.

[04blackgmc]

I set Tip-In and Shift Ctrl Termination back to stock and downshifts feel softer...or its all in my head.

right now my car feels great to me.. i feel as if its not too aggersive yet does great wot and partial throttle.