6L80 / 6L90 Line pressure. Everyone is wrong

[hjtrbo]

Right, going to make a statement about stock 6L80 / 6L90...

Raising the max pressure, max pressure B, max clutch & max line pressure tables does nothing on a stock unit to increase line pressure. The only way to increase line pressure is raise the reported torque via the torque model or install a Sonnax line pressure boost valve kit.

Someone with a pressure gauge hooked up to the test port tell me I'm wrong.

If no one can, then why does everyone raise these tables? (Guilty of it myself)

Nothing mean intended here team. Just seeing a lot of stuff getting changed but no one ever providing data to back up the change. Happy to be taught a new thing today.

[5FDP]

I've never touched those tables in any tune I make either.

[mach]

part throttle pressure tables as well? or just max? have you confirmed either with gauge? ive not checked myself honestly, although i had planned to at some point

[hjtrbo]

Pressure everywhere except shifts.

I also plan on hooking up a gauge. My intent with my first post is to start a big fire and see if anyone has data to put it out. We'll all learn something if that is the case.

I've been monitoring PCS 1 pressure (line pressure control solenoid) for some time now and that never changes log to log when I change the tables mentioned in my first post. Only time it increases is when I raise the torque tables. PCS 1 does increase with shift pressure increase so no argument there.

Need Cody from Precision Transmissions to do a video on it.

[sevinn]

Pressure everywhere except shifts.

I also plan on hooking up a gauge. My intent with my first post is to start a big fire and see if anyone has data to put it out. We'll all learn something if that is the case.

I've been monitoring PCS 1 pressure (line pressure control solenoid) for some time now and that never changes log to log when I change the tables mentioned in my first post. Only time it increases is when I raise the torque tables. PCS 2-5 do increase with shift pressure increase so no argument there.

Need Cody from Precision Transmissions to do a video on it.

Well, it's a clamp not a setting. If you raised torque to where it was referencing beyond that value it would clamp there.

[hjtrbo]

Nice.

Nearly every tune I see on this forum has them raised significantly. Even my original tune from big name Melbourne tuner has them raised.

Max mechanical spring pressure limit of the pump (2000kPa 6L90) is achieved at approx 800kpa pcs 1 signal pressure. I've seen tunes with the max pressure table set to over 2000 on stock builds here. Look at some posts, you'll have people say you need to raise it up when you add a cam or bla bla or you will toast your trans.

[sevinn]

Nice.

Nearly every tune I see on this forum has them raised significantly. Even my original tune from big name Melbourne tuner has them raised.

Max mechanical spring pressure limit of the pump (2000kPa 6L90) is achieved at approx 800kpa pcs 1 signal pressure. I've seen tunes with the max pressure table set to over 2000 on stock builds here. Look at some posts, you'll have people say you need to raise it up when you add a cam or bla bla or you will toast your trans.

It's true and untrue at the same time. Tuner can put all the pressure they want in the shift tables but if the clamp is too low it won't reach commanded.

[hjtrbo]

Getting closer to my point. The stock values in the 6L90 are so close to the maximum pump pressure that raising them would show nothing.

[Millsy]

Would love to know who it is. I've seen some terrible 6L80/90 tunes from big name workshops country wide. They treat it like a 4L60/65 tune.

[hjtrbo]

Never mention it. They did some good in other areas. But some more info if anyone wants to infer line pressure without a gauge... Credit to carneb and Chris@hptuners

[JustinWhiteTuned]

Right, going to make a statement about stock 6L80 / 6L90...

Raising the max pressure, max pressure B, max clutch & max line pressure tables does nothing on a stock unit to increase line pressure. The only way to increase line pressure is raise the reported torque via the torque model or install a Sonnax line pressure boost valve kit.

Someone with a pressure gauge hooked up to the test port tell me I'm wrong.

If no one can, then why does everyone raise these tables? (Guilty of it myself)

Nothing mean intended here team. Just seeing a lot of stuff getting changed but no one ever providing data to back up the change. Happy to be taught a new thing today.

EHHHH ok so the way that works is it is the allowed limit based on shift characteristics and adaptations, i can actually get some data to prove that possibly just gotta go find my old logs with the inducers on the VB. The tcm will always try to use less pressure as long as adapts are enabled and the shift is completeing within a percentage of commanded, hence why the trans always softens up with adapts. Setting that too high, if you have some improper shifts or failing clutches, ive seen blow the snapring out of the drum as well as broken shafts and planetaries. The reported torque also is a huge factor in how much of that clamped amount it will use based on what power it thinks its seeing, as well as shift characteristics.

[Jet Mechanic]

Hmmm.... I'm wondering if this may be my problem with my trans tuning?? I will attach my current tune if anyone would care to look and see what may be wrong.....

Some info...... the car is a 2007 Corvette 402ci, whipple supercharged, 6L80E fully built making 811/787...... I run the trans ALWAYS 1qt overfull and am sure that it is never low. Two different times I've had it back out and to the trans shop, and each time they say the damage looks like a "low fluid level" condition and that the clutches and steels are shot. I'm very new to the tuning side of things....and don't want to cause harm with stupid mistakes....

I'm wondering how to "raise the reported torque" in the torque model? or how to tell if I need to raise it?

Secondly, I'm wondering about the Shift Timing> Transition time> Initial normal and special as well as > Final normal and special?..... Seems to me that when you increase the HP and TQ, you would need to shorten the transition time of the shift to prevent slip? Thus preventing slippage and burning of the clutches, but is there a limit to how much you can "shorten" the shift? The transmission needs time to shift....but how much time??

My clutch and steel damage issue isn't from LOW fluid level....so, I'm assuming it's a "clamping" issue or a "shift transition" issue

Any suggestions would be appreciated!!

Rod.. in TX.....

[blindsquirrel]

Aerated, foamy fluid from an overfull condition lubes about the same as not enough fluid.

[Jet Mechanic]

Aerated, foamy fluid from an overfull condition lubes about the same as not enough fluid.

I get that.... but any, reputable builder can weigh in on this..... Everyone that I know, will tell ANY 6L80E owner to run the trans (in Corvettes) 1 quart over what GM recommends for proper filling. Also, I have no way of checking for aeration unless anyone can suggest an idea?? Clear, see through tubing on the cooling lines maybe??

[cadillactech]

I get that.... but any, reputable builder can weigh in on this..... Everyone that I know, will tell ANY 6L80E owner to run the trans (in Corvettes) 1 quart over what GM recommends for proper filling. Also, I have no way of checking for aeration unless anyone can suggest an idea?? Clear, see through tubing on the cooling lines maybe??

When you say fully built 6l80E, what do you mean exactly?

Were all clutch clearances checked after upgrades parts were installed? I have seen shops just throw in stage 3 or stage 4 clutches, not check the clearances and burn up a "fully built" trans because the clutches were either bound up or not fully applying.

Most manufacturers of the upgraded steels and clutch discs will give you new spec range to shoot for. Just make sure you are ruling out the mechanical side before the calibration is looked at.

Overfilling about .75 qts is what Circle D recommends on any serious track use but you should make sure to adhere to the proper fill procedure first and then add the additional fluid.

[Jet Mechanic]

When you say fully built 6l80E, what do you mean exactly?

Were all clutch clearances checked after upgrades parts were installed? I have seen shops just throw in stage 3 or stage 4 clutches, not check the clearances and burn up a "fully built" trans because the clutches were either bound up or not fully applying.

Most manufacturers of the upgraded steels and clutch discs will give you new spec range to shoot for. Just make sure you are ruling out the mechanical side before the calibration is looked at.

Overfilling about .75 qts is what Circle D recommends on any serious track use but you should make sure to adhere to the proper fill procedure first and then add the additional fluid.

Well.....to answer your question directly on "fully built" ..... Mike Kurtz and Ronnie at Century Automotive and Transmissions in Richmond TX are very well known in the Corvette world for building 6L80E's for the Corvettes....They build these transmissions to hold 1600+ HP. My transmission has had every upgrade and update that is possible (for the power levels that I'm at). The only thing that I have not upgraded on my transmission is the planetary set. They offer a billet planetary set for my trans but didn't think it was necessary since I'm only at 811/787.....

As for the overfill.... Ronnie is the one that recommended a minimum of 1 quart (and up to 2 quarts) overfull..... He indicated that the worst thing that might happen from being too full, would be that the fluid would come out of the vent. He didn't think that aeration or foaming would be an issue because of the design of the trans......

You can find out all kinds of info on Mike and Ronnie on the Corvette forums and people's experiences and recommendations..... I'm just going with what I know and have been told. blindsquirrel brough that up in the comments above.... and the only way I can think of observing any foaming or aeration would be to put in a section of clear line in the cooling lines???

The main reason I'm on this thread is because I don't know how to determine if the comment that hjtrbo mentioned..."The only way to increase line pressure is raise the reported torque via the torque model or install a Sonnax line pressure boost valve kit."..... I don't know how to check or change the "reported torque" values in a Tune. Yet again... I think I have "clamping" (pressure issue) or possibly the transition time of the shifts may be allowing the slippage which is burning up the clutches and steels....

I posted my tune above.... for others to look at and see if there is something amiss..... and just like hjtrbo posted in his pic, MY pressures have been adjusted WAY up.....

I just spent the past 2 hours putting together a data logging channel that my car supports (2007 Corvette E38 PCM, T43 TCM).... and will data log everything the next runs at the track and maybe that will be helpful.

[Jet Mechanic]

When you say fully built 6l80E, what do you mean exactly?

Were all clutch clearances checked after upgrades parts were installed? I have seen shops just throw in stage 3 or stage 4 clutches, not check the clearances and burn up a "fully built" trans because the clutches were either bound up or not fully applying.

Most manufacturers of the upgraded steels and clutch discs will give you new spec range to shoot for. Just make sure you are ruling out the mechanical side before the calibration is looked at.

Overfilling about .75 qts is what Circle D recommends on any serious track use but you should make sure to adhere to the proper fill procedure first and then add the additional fluid.

Also.......I run a Circle D 258mm single disc converter that was spec'd by them for my combo......

[dhoagland]

Hmmm.... I'm wondering if this may be my problem with my trans tuning?? I will attach my current tune if anyone would care to look and see what may be wrong.....

Some info...... the car is a 2007 Corvette 402ci, whipple supercharged, 6L80E fully built making 811/787...... I run the trans ALWAYS 1qt overfull and am sure that it is never low. Two different times I've had it back out and to the trans shop, and each time they say the damage looks like a "low fluid level" condition and that the clutches and steels are shot. I'm very new to the tuning side of things....and don't want to cause harm with stupid mistakes....

I'm wondering how to "raise the reported torque" in the torque model? or how to tell if I need to raise it?

Secondly, I'm wondering about the Shift Timing> Transition time> Initial normal and special as well as > Final normal and special?..... Seems to me that when you increase the HP and TQ, you would need to shorten the transition time of the shift to prevent slip? Thus preventing slippage and burning of the clutches, but is there a limit to how much you can "shorten" the shift? The transmission needs time to shift....but how much time??

My clutch and steel damage issue isn't from LOW fluid level....so, I'm assuming it's a "clamping" issue or a "shift transition" issue

Any suggestions would be appreciated!!

Rod.. in TX.....

I'm no expert, Just trying to help you with Virtual Torque
The picture is from your posted Tune, just expanded the view.

You say you are making 800 TQ...
Lets pretend that number is at 1300mg Airmass, 25 degrees of timing, and 6400 RPM.. Your torque model shows 823, You're good.
Now lets say you make 600 TQ at 700mg Airmass,25 degrees of timing and 4800 RPM... Your torque model shows 432, we have an issue.

[Jet Mechanic]

I'm no expert, Just trying to help you with Virtual Torque
The picture is from your posted Tune, just expanded the view.

You say you are making 800 TQ...
Lets pretend that number is at 1300mg Airmass, 25 degrees of timing, and 6400 RPM.. Your torque model shows 823, You're good.
Now lets say you make 600 TQ at 700mg Airmass,25 degrees of timing and 4800 RPM... Your torque model shows 432, we have an issue.

Hey..... thanks for the reply...
So, I will start out with I'm Very new to the tuning thing...

In reference to your examples...... I just set up a better channel of data logging for the car and went out for a loop around my local area where I could do some aggressive pulls.....with the intent to see what the 2-3 shift and 3-4 shift looked like. In just one of the very short pulls the during the 2-3 shift, looking at the data...... just before the shift> RPMs=5498, cylinder airmass=2262mg, timing=22 degrees, and it took 1.31 secs for the shift to complete. During the shift the cyl airmass dipped to 1205mg at the low point and at final shift pressure (110 psi) it rose back to 1774mg.......

I can scan my dyno sheet but this car (per the dyno sheet) makes 740+ TQ at 5500RPM at 1:1

Based on how I understand your examples..... "Houston, we have a problem"

Wouldn't you agree? Did I give you the necessary info to see where I'm at.......

Thanks in advance for your insight and help!! If you need more info....let me know....

Rod...

[dhoagland]

Hey..... thanks for the reply...
So, I will start out with I'm Very new to the tuning thing...

In reference to your examples...... I just set up a better channel of data logging for the car and went out for a loop around my local area where I could do some aggressive pulls.....with the intent to see what the 2-3 shift and 3-4 shift looked like. In just one of the very short pulls the during the 2-3 shift, looking at the data...... just before the shift> RPMs=5498, cylinder airmass=2262mg, timing=22 degrees, and it took 1.31 secs for the shift to complete. During the shift the cyl airmass dipped to 1205mg at the low point and at final shift pressure (110 psi) it rose back to 1774mg.......

I can scan my dyno sheet but this car (per the dyno sheet) makes 740+ TQ at 5500RPM at 1:1

Based on how I understand your examples..... "Houston, we have a problem"

Wouldn't you agree? Did I give you the necessary info to see where I'm at.......

Thanks in advance for your insight and help!! If you need more info....let me know....

Rod...

I'm a little out of my League here. I understand it but have no practical experience at it.

That being said you need to match Your actual torque to the Virtual torque model in your tune.
So if your Dyno sheet had torque numbers with Airmass that would be Awesome, I'm sure it doesn't.
You could probably use the chart against a hard pull, look at your Airmass and compare it to get an idea.

I know you can use the engine delivered torque in the scanner to give an idea of where your at.
But that also assumes all your air models and stuff are correct. I saw you are SD, I'm not sure if you need MAF to have delivered engine torque display accurately in the channels.

Where in North "H" Town are Ya?
I stayed in Decker Prairie from 09-14, working on Metro Rail extension Down Town.