Concise definition of oncoming/offgoing pressure and clutch volume?

[DSteck]

Does anyone have a definition of the oncoming pressure preset, offgoing pressure preset, and clutch volume preset? I am mostly interested in knowing specifically how the values are used when completing a shift. I have found bits and pieces but I'm hoping for something cut and dry. ie: What specific function does each one perform?

[LSX378]

Does anyone have a definition of the oncoming pressure preset, offgoing pressure preset, and clutch volume preset? I am mostly interested in knowing specifically how the values are used when completing a shift. I have found bits and pieces but I'm hoping for something cut and dry. ie: What specific function does each one perform?

They are the presets for the adapts.

[DSteck]

They are the presets for the adapts.

I was more looking for information on how those variables come into play. How does adjusting them impact the shift properties, etc. I'm mostly curious how oncoming an offgoing are used in conjunction with one another.

[rynez06]

would like a more clear definition on this as well

[Chris@HPTuners]

the oncoming pressure preset is the base point for the oncoming (applying) clutch during the shift

the offgoing pressure preset is the same for the offgoing (releasing) clutch.

the volume adapt is used to calculate the fill time becuase around the time the clutch is estimated to be full the offgoing clutch pressure is dropped. It also provides feedback to the logic that pressure related issues can be identified becuase the clutch is "full". ie. there is no point adapting offgoing pressure if the symptom of the poor shift relates to the oncoming clutch being overfilled.

they are all adapted depending on how the shift actually executed and whether torque and throttle indicate it was a powered or unpowered shift.

Some examples:
- if flare occurred early in an upshift it means the offgoing pressure was too low to hold the old gear while the new clutch is applying.
- in the case that the new gear engages early it could be an overfill condition before the offgoing pressure release occurs so an oncoming volume adapt might be necessary
- if a flare occurs after the oncoming clutch is full and the offgoing clutch pressure is dropping it means the oncoming pressure is too low
- if the new gear engages late and a flare occurred it means the oncoming didn't have enough pressure or volume or both

there are complicated aritration algorithms that identify all kinds of timings, torque rampings and flare identification, that influence either the oncoming or offgoing pressure or the oncoming volume.

if you have mofied your trans to include more clutch packs or thicker materials, then likely you will need to reduce the volumes. you can mess with the adapts if you specifically can see flaring or any other symptoms of shift binding etc.

In general so long as you have the starting points close the code does a great job of adapting.

Hope that helps,

Chris...

[DSteck]

That was effing awesome. I was especially interested to know the function of offgoing pressure. Now I understand the point of it. Thanks!

So if you are feeling generous... Care to offer more info on the use of the turbine acceleration tables?

[edcmat-l1]

They sound like Chrysler CVI (clutch volume index). In the Chryslers, the CVIs were used mainly to help diagnose trans problems (excessive CVI=worn clutches=slipping trans). I can see how the same information can be used by the computer to adapt the shift times, pressures, firmness (or opposite).

Even without an explanation of them, this is the way I thought if them, because in my little coconut, that's what made sense. Having it explained reaffirms this.

[madvette08]

That was effing awesome. I was especially interested to know the function of offgoing pressure. Now I understand the point of it. Thanks!

So if you are feeling generous... Care to offer more info on the use of the turbine acceleration tables?

I always thought those tables had something to do with the torque converter during the shifts. But i could be wrong and that's about all i know on those lol.

[DSteck]

I always thought those tables had something to do with the torque converter during the shifts. But i could be wrong and that's about all i know on those lol.

I'm pretty sure that's what they are for, but I am hoping to get an explanation of how they are used and applied.

[Tick]

Bringing this one back from the dead.... What would happen if the oncoming and offgoing pressure presets as well as the oncoming volume preset was drastically different that stock? Would this create excessive wear or even failure of the transmission?

I'm tuning a 2011 CTS-v with different pulleys, headers, camshaft, and 2800 stall. It was previously tuned and had some shifting issues. I changed the trans parameters back to stock and put more normal values in the "shift time torque adder" and "base shift pressure" tables as well as the tcc apply ramp for the stall. Torque management is disabled.

I'm getting a flare on the 3-4 shift with medium load. I've played around with the shift time and base pressure without having much luck.

Attached is the tune as it came to us and the tune after my initial changes.... The trans shifted pretty harshly as it came to us and it would jerk and generally feel rough when the converter would unlock in 6th gear once enough throttle was applied. With the changes I made the unlock issue seemed to go away and the shift feel everywhere seems a lot better except for the 3-4 flare and harsh shift from 2-3 occasionally. Please feel free to take a look and offer any advice on my issues or any of the changes I made and I'm new to these six speed autos.

[V locity]

Try adjusting your 2-3 base pressures like these tables:


then for the 3-4 flare, try scaling your MAF * 1.1 and report back the results of the shifting...

[edcmat-l1]

then for the 3-4 flare, try scaling your MAF * 1.1 and report back the results of the shifting...

You do realize scaling the MAF all by itself will do nothing except throw the fuel trims off, right? What you're trying to do, you should be scaling the VE, the MAF, and the IFR all by the same %.

[V locity]

The MAF scaling is a test for DTQ. Hence the report back.

[Turbo Ryan]

the oncoming pressure preset is the base point for the oncoming (applying) clutch during the shift

the offgoing pressure preset is the same for the offgoing (releasing) clutch.

the volume adapt is used to calculate the fill time becuase around the time the clutch is estimated to be full the offgoing clutch pressure is dropped. It also provides feedback to the logic that pressure related issues can be identified becuase the clutch is "full". ie. there is no point adapting offgoing pressure if the symptom of the poor shift relates to the oncoming clutch being overfilled.

they are all adapted depending on how the shift actually executed and whether torque and throttle indicate it was a powered or unpowered shift.

Some examples:
- if flare occurred early in an upshift it means the offgoing pressure was too low to hold the old gear while the new clutch is applying.
- in the case that the new gear engages early it could be an overfill condition before the offgoing pressure release occurs so an oncoming volume adapt might be necessary
- if a flare occurs after the oncoming clutch is full and the offgoing clutch pressure is dropping it means the oncoming pressure is too low
- if the new gear engages late and a flare occurred it means the oncoming didn't have enough pressure or volume or both

there are complicated aritration algorithms that identify all kinds of timings, torque rampings and flare identification, that influence either the oncoming or offgoing pressure or the oncoming volume.

if you have mofied your trans to include more clutch packs or thicker materials, then likely you will need to reduce the volumes. you can mess with the adapts if you specifically can see flaring or any other symptoms of shift binding etc.

In general so long as you have the starting points close the code does a great job of adapting.

Hope that helps,

Chris...

Awesome information Chris.

Looking at what you have posted, I would think with some logging of my shift issues, I can determine what is causing my momentary lag or intermittent flare from 2nd into 3rd.

Isolating when the flare occurs and using your information I can determine its cause and attempt to smooth iot out by manipulating those tables.....

Now..I must figure out what and how to log this information lol

Ryan

[G8-4-speed]

Good stuff...

[Turbo Ryan]

Good stuff...

Most certainly is!

[mrgillies]

I have a similar issue I'm working with Mike @ Century on a built 6l80e (C6) where my 2-3 seems to lag then feels like it jams (bumps) into gear, all other shifts are fantastic

He's changed these tables that I have not yet tried

Shift Time
Upshift Special 2-3 Sp (increased about 40 % on cells Bottom left to 4000rpm diagonally)

Shift Pressure
Base Shift pressure Upshift 2-3 Upshift x and Y (lowered values by around 30 on colums 0,111,221)
Max adapt volume Max 2-3 (changed from 40 to 100)

Just in case that helps anyone

[DSteck]

Only at part throttle? That is almost unavoidable when you delete the wave plate.

[thesubfloor]

I have a similar issue I'm working with Mike @ Century on a built 6l80e (C6) where my 2-3 seems to lag then feels like it jams (bumps) into gear, all other shifts are fantastic

He's changed these tables that I have not yet tried

Shift Time
Upshift Special 2-3 Sp (increased about 40 % on cells Bottom left to 4000rpm diagonally)

Shift Pressure
Base Shift pressure Upshift 2-3 Upshift x and Y (lowered values by around 30 on colums 0,111,221)
Max adapt volume Max 2-3 (changed from 40 to 100)

Just in case that helps anyone

If the problem you're referring to is the feeling like the car is actually downshifting just before shifting into 3rd, I stumbled across a fix purely by accident.

To see if it'll also work in your case, try driving the car in both Drive and Sport mode. If you experience the problem in Drive but not Sport then you'll be able to get rid of it by making changes in your tune.

[mrgillies]

I Have it in both modes, my issue is the car seems to just hang in gear then after what seems forever (1/2) sec it then jumps in gear, its more pronound at lower throttle positions, higher demand it isn't anywhere near as bad