Concise definition of oncoming/offgoing pressure and clutch volume?

[thesubfloor]

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

Email me if you want and I'll send you my tune tonight to see if it helps any.

[email protected]

[mrgillies]

Email Sent, thanks

[ragged-edge]

I would bet that 90% of the shift issues I see are related to valve body wear. Try vacume testing your valve body even on brand new reman unit and you will find that they are borderline. When you start ramping pressures in is where they really start to cross leak. The back side of that is that the tuner really should be dictating the stack up tolerences, wave plate removal, ect. to the builder. 9/10 times the math is wrong when aftermarket clutches are involved, especially when you start removing wave plates, adding clutches, and ramping pressures.

[wayneosan]

Ok. Just doing some logging on a stock 2011 CTSV.

Take a look at the current gear and then commanded pressures. It looks like the pressures build up and release clutch pressures before the shift actually takes place. Even the tq reduction timing hasn't even started yet. All I have is commanded pressure, is there actual pressure I can log? It seems like the stock trans can't mechanically shift faster, possibly valve body upgrading necessary.

Just take a look at Oncoming clutch data. Then look at when the retard begins.

I was just toying with getting the shift times quicker without turning off tq reduction completely. Downshifting is horrible from 6-2 stock.

What does the Y axis label stand for on "oncoming" clutch and "offgoing" clutch? I looked to me like an inertia factor profile value.
I just want a shift that's clean like in my truck.

[ProFire]

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...

Hate to bring old threads back to life but I haven't been getting any hits on my thread. I am having a binding issue as chris explained in the Quote above. I am new to working on these volume and pressure areas of the trans and just want to make sure I am changing the right things and know why I'm changing them and how they work. I have a 6l80 with additional clutches (Alto), Sonnex pistons, line booster and zip kit. 1-2 bad, 2-3 is the worst, 3-4 not too bad, 5-6 and 4-5 are moderit.

So in his examples he says "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". So I see Oncoming Volume Preset and Max Volume Adapt. I believe this is where I need to be working but which one should I work on and in which direction? If I am in fact having an overfill issue than I would assume I will need to decrease the volume.?

Next question is about procedure. Change volume, download, KOEO reset and preset, then try it out?

[32vape]

Hate to bring old threads back to life but I haven't been getting any hits on my thread. I am having a binding issue as chris explained in the Quote above. I am new to working on these volume and pressure areas of the trans and just want to make sure I am changing the right things and know why I'm changing them and how they work. I have a 6l80 with additional clutches (Alto), Sonnex pistons, line booster and zip kit. 1-2 bad, 2-3 is the worst, 3-4 not too bad, 5-6 and 4-5 are moderit.

So in his examples he says "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". So I see Oncoming Volume Preset and Max Volume Adapt. I believe this is where I need to be working but which one should I work on and in which direction? If I am in fact having an overfill issue than I would assume I will need to decrease the volume.?

Next question is about procedure. Change volume, download, KOEO reset and preset, then try it out?

You ever get this resolved? I am having the exact same issue on a similar build 6l80. Lowering the volume preset and minimum volume 10% seemed to help a little but not solve the issue.

[cmitchell17a]

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...

Can you explain how the TCM measures this "volume"? As far as I know the only feedback the TCM has on any physical parameter in the trans is the input and output speed (I believe the 8L80 has an intermediate speed sensor?) and the hydraulic pressure at some points. So I would imagine an arbitrary volume is calculated based on the flow of the solenoids. But I don't understand why they use volume if the fluid is incompressible? I don't understand why it isn't just pressure based? Is there any hydraulic schematics of any of these transmissions anywhere?

[camarolsx16]

Profire, did you every get answer for this, my 6l90e has added clutches, my trans tuner has my 2-3 volume preset set to 10 and my 3-4 set to 0. i have broken two intermediate shafts in less than two weeks apart because of 3-4 shift. my pressures do no go 1500kpa and tm is still on 40%. Any help would be greatly appreciated! I've got a billet shaft on order now!

[5FDP]

He also has alot more shift pressure than stock and a way faster requested shift time of .1748s at 5,000+ rpm. I'd reduce the shift pressure by 20psi and raise the time to .2500 to keep it the same as 0-4750rpm. The on-coming pressure presets are also raised quiet alot, lowering them in the "2" row might help too.

It's like it was setup for a on kill tune all the time at medium to heavy throttle.

[jfortvalley]

When you are having your 2-3 issue are you letting car warm up and did you learn the transmission by driving it for a little while