Lockup strategies and their affect on clutch durability.

[jakeshoe]

OK, I'll play...

Don,
I think anybody somewhat familiar with GM transmissions in general, and the differences between a modulated line pressure and a TV system can understand the differences here.

OLd style GM 3 speed, engine vacuum (or lack thereof)= greater engine load. This causes the modulator valve to increase line pressure. Nearly instantaneously, as you said real-time input.

The TV cable is USUALLY a linear device and therefore cannot in anyway except throttle position determine the input torque delivered from the motor.
So in effect a STOCK TV cable geometry will not compensate for a motor that makes huge torque down low. Say a 500+ cube BBC with a supercharger. Instant torque delivery at even a very low throttle angle when the TV system hasn't gotten the line pressure up to higher levels.

As Chris stated he expects to see a linear rise in line pressure with throttle opening.

I think a "bellcrank" linkage could be made to cause a more pronounced rise in line pressure at lower throttle openings, and then level off near WOT. This would work better on huge torque motors.

However a TH400 and Gear Vendors unit would work well and be about the same price, better longetevity IMO..

 

[chris718]

very interesting point jake.we have a unique way of doing this for this application.it is by the size of the modulated tv oil hole size in the seperator plate that acts on the boost valve.

 

[jakeshoe]

Chris,
The way I understand it is that even a stock unit has a pretty good instant rise in line pressure at any movement of the TV plunger.
I would think that for the "average" application, a typical shift kit with heavier PR, bigger boost valves would take care of any NA motor, and likely most turbo motors since thay have to spool up.

However I used a large BBC with Supercharger as an example because in that case I think the tremendous torque at any slight throttle increase would be beyond the capabilities of a stock linear TV cable geometry.

In a case liek that that is mostly a track car anyway, would a full manual VB setup work keep full line pressure at all times like a 3 speed?

I don't care for the full pressure all the time technique but sometimes it is a necessary evil.

Especially don't care for it on the vane type pumps...

 

[chris718]

this is why factory performance units shift harder at low throttle angles and get soft upstairs.accumulator trim pressures are less at wot than in the mid range with stock calibration.the theory was high torque buildup downstairs needed a higher initial ratio but this caused sloppiness at wot even at max line because of accumulator circuitry.i dont like fixed line either and dont see the need for it if one has time to calibrate,

 

[Alky V6]

I haven't been on this BB for quite some time, but I can tell you for sure that jakeshoe IS a very good transmission technician. Very good info. I agree with you on every point.

It should be clear by now that the 200-4R in stock form is calibrated to follow the stock engine torque curve only and when engine mods are done to change that torque curve, you need to go into the trans and make various mods so that the transmission has the correct pressures at the correct moments in engine operation to minimize the chance of excessive slippage of a friction element (band or clutch pack). Discounting the torque converter clutch for the time being. If anyone is still unclear on this, please post a question so we can make sure we don't leave anyone behind.

One of the characteristics of the turbo valve bodies is the smaller than usual (N.A. V8 applications) small land diameter on the throttle valve. What do you think is the result of this difference in area? This one would be for the techs out there.

Very soon we'll start getting to the torque converter clutch (TCC) design parameters. We'll start with the stock converter that comes with our cars.

Until later.

 

[Alky V6]

Ok. Lets get this ball rolling.
The OEM converter uses a paper clutch lining not known for its ability to take a lot of slippage and heat. By looking at the design of the unit and area of the clutch material, it was not intended to hold under too much torque. I am aware that there are some published figures of the torque capabilities of some GM lockup units. They mainly have to do with the dampeners abilities. Maybe someone has those handy and can share them. The GM programming of any lockup strategy that I have personally witnessed (through test drives only) is very considerate of engine load vs lockup timing. The reason is simple. The torque converter lockup feature was designed for one purpose only. Increased gas mileage through the elimination of undesirable slippage in the torque converter under CRUISE situations. The desire to have the converter clutch handle moderate to high load was never a consideration in its design. As many have found out by now, you'll get away with locking it up under load for a little while, but it will catch up to you eventually. Some sooner than others. Does anyone have the actual areas for the OEM 11" and 9" lockup linings? In the next postings I would like to start discussing the different modifications (mechanical and hydraulic) that are available to increase clutch torque load capacity of the L/U clutch converter.

 

[Firechicken]

Don are you still around? I just found this thread and find it very interesting and informative.

I hope that despite the long period between posts, that you will please continue with the discussion, partcularly in the area you have eluded to regarding the mechanical and hydraulic modifications to increase the clutch torque load capacity of the locking clutch.

 

[HellOnWheels]

Don are you still around? I just found this thread and find it very interesting and informative.

I hope that despite the long period between posts, that you will please continue with the discussion, partcularly in the area you have eluded to regarding the mechanical and hydraulic modifications to increase the clutch torque load capacity of the locking clutch.

Same here Don.

 

[chris718]

GUYS I JUST READ MY POST NUMBER 40 AND FOUND THE LASTsentence amusing.thanks for bringing it back ,i had a rough day and just made myself laugh hard.damn i post some strange things from time to time as well as get agreesive,very amusing however.

 

[ITSAV6]

????

Chris,
The way I understand it is that even a stock unit has a pretty good instant rise in line pressure at any movement of the TV plunger.
I would think that for the "average" application, a typical shift kit with heavier PR, bigger boost valves would take care of any NA motor, and likely most turbo motors since thay have to spool up.

However I used a large BBC with Supercharger as an example because in that case I think the tremendous torque at any slight throttle increase would be beyond the capabilities of a stock linear TV cable geometry.

In a case liek that that is mostly a track car anyway, would a full manual VB setup work keep full line pressure at all times like a 3 speed?

I don't care for the full pressure all the time technique but sometimes it is a necessary evil.

Especially don't care for it on the vane type pumps...

The line psi on my PTS unit are close to 300 at 1/2 throttle. It would be nice to have a pwm solenoid in the circuit that would keep the psi a little lower till the boost came on then ramp it up with the boost. But it would need a stand alone controller,lots of R&D,and prob wouldn't be worth the $'s

 

[WE4]

I HAVE to jump in here...

I am not going to get in the middle as I am enjoying reading rather than typing.
But DAMMIT, Don starts a thread to learn and discuss in and it turns into who knows more thread? COMON GUYS!!!!!! Be Friggin ADULTS here!!!
How can we carry on a valid informative conversation or thread if it turns into a who knows more crap.
I hate this about these type of threads. It COULD and HAS THE POTENTIAL to be very informative and it turns into a free for all?
WTF?
I want this thread to go on as it has alot of good info in it and can possibly have more, but if I have to start editing peoples (You know who) threads so they can get along, I will. Comon guys, grow up and participate, not argue. Like I said before, BE ADULTS!!!!!
Don brought a great point to the table and as you see has donated quite abit of time to what he posted. He also asked that others CONTRIBUTE or ADD to not argue or a contest to see who is the most know it all. We ALL can learn from this and I want it to stay so Like I said, If I have to edit the negs out I will, but please, please, do not force me to go there. Please?

Let's be adults and have a very informative, maybe even learn something new thread.
That's all for now

Bruce
WE4
Tb.com admin.

 

[jakeshoe]

Bruce,
This thread is OLD... look at the time stamps.
Don hasn't been back to finish what he started.

 

[turbo2nr]

Big Bang-Dinosaures-Ice Age-WWII-Buick GN-something about converters-

 

[Alky V6]

The line psi on my PTS unit are close to 300 at 1/2 throttle. It would be nice to have a pwm solenoid in the circuit that would keep the psi a little lower till the boost came on then ramp it up with the boost. But it would need a stand alone controller,lots of R&D,and prob wouldn't be worth the $'s

Wow! This thread is still around?

I had some personal family problems crop up during the time this thread was going on and was hoping someone else would take the torch with this subject. Anyone with teenage boys can relate. My concerns were elsewhere at the time. Then, I was deeply involved in my Stage I project. Now, my engine is down, waiting for parts and I am bored.

Ok, let's see if we can tap into the abundance of knowledgeable people that frequent this bulletin board and come up with some insightful brain storming.

itsav6 brought up an important point. I will try to explain why so much pressure, so soon in the throttle percentage is necessary in most cases with these wonderful cars.

At this time in the Buick Grand Nationals life span, the evolution is at the point that most people that decide to modify their prize possession go pretty radical. The technology that is available seems to push people to that level. The past and current thinking in terms of turbo spool up time is, the quicker the better and the aftermarket is abliging everyone with this request. The big problem with that is the transmission is calibrated to raise line pressure with a particular plotted curve in relation to the engine's torque curve. When you make that torque curve rise vasting steeper in relation to throttle opening percentage, big problems with the transmission WILL occur. You will have burned friction elements because the required hydraulic line pressure was not there when it was needed. For instance, at 30% throttle the stock engine may develop 175 ft lbs torque. You modify the engine or/and chip, do things to quicken the turbo spool up and the engine now develops 275 ft lbs torque at the same throttle opening. The TV cable is being pulled the same amount in both instances, so the transmission is delivering the same amount of hydraulic pressure to its friction elements. With the added torque that the engine is now trying to transfer through the band and clutch packs, they can't hold and will slip, causing them to overheat and burn. Once they're burned even a tiny bit, the friction elements ability to hold under torque is greatly deminished and it's only downhill from then on. I know the techs out there are falling asleep, but I do understand that some people reading this thread are new to the workings of transmissions and I would hope that if a tech contributes to this thread, they try to write, understanding that your teaching here also.

Now, the engine tuning combinations that are available to people are endless these days. That means the engine torque curve could be anything. Recognizing that, a transmission technician will, for obvious reasons try to cover his s, and give the transmission an agressive line pressure rise. In the old three speed days, a vacuum modulator allowed the transmission to change line pressure rise in relation to intake manifold pressure. A much better system than the current cable systems when it comes to high performance. With the old three speeds, if it was a balls to the wall application, full line pressure was supplied at all times. That is the safest way to insure that the clutchs have the needed hydraulic line pressure at the right time. The problem with high line at times when it really isn't needed is it places unneeded stress on the pump components. With the gear and cresent pump, the only concern is the pump body bushing wearing out prematurely. With a vane pump, this arrangement is weaker than the gear pump and pump component failure is always a concern, along with the bushing wear concern.

I feel it is a very brave attempt for a transmission technician to customize the transmission's line rise to the engine's torque curve. It is so much easier to just lock out the line pressure (high) and not worry about the kind of torque rise curve the particular customer's car has. But remember, we don't want a vane pump running at high line pressure more than it has to.

Back to TCC clutch capacity. What are the variables or parameters that will affect TCC lock up apply time and feel? What are the dangers of some of these variables getting adjusted too far to the extreme?

 

[NHRA Super Gas]

Basic Question

OK, for the guys who are or want to run 11.50's or so and drive the car on occasion to cruise nites etc, not necessarily every day. This person is likely using a 3K or so converter. What is a good strategy for lockup and at what MPH?

 

[Alky V6]

OK, for the guys who are or want to run 11.50's or so and drive the car on occasion to cruise nites etc, not necessarily every day. This person is likely using a 3K or so converter. What is a good strategy for lockup and at what MPH?

That is not a simple question. Lets look at some of the questions that need to be answered first.
How important is it to eek out every last tenth of a second? Trading durability for time slip.
Has the transmission been upgraded?
Has the L/U circuit of the transmission been modified?
What is the diameter of the TC clutch?
Is the TCC friction stock size or been increased?
Is it single disc or multi-disc?
Is the TC using a TCC dampener assembly?
Will the stock ECM be used? If so, how much experience does the person burning the chip have with different L/U stradegies? Different L/U stradegies with your particular type of transmission modifications and torque converter type and configuration?
What is the torque curve of the engine? This will be important if your TCC is not designed to take a lot of torque and the person burning your chip would want to set the lock point well away from high torque points in the map/rpm table.
As you can probably start to see, it is not that simple of an answer.
I'm sure there are other areas of the equation I'm missing, but hunger is setting in. Time to eat dinner. Later.

 

[chris718]

in my opinion 300 psi at 45 degrees of throttle angle or half throttle is insane.with our tech and the dual feed in high gear there is actually way over 1000 psi applying and holding the direct clutch.if you simply go on a dyno to view your torque curve you can size the modulated tv oil hole in the plate to properly ramp oil psi in relation to torque.also like ive been saying all along the use of the mcss valve body or its longer tv plunger spring.sizing up to .080"can be used for instant ramp up but this is very seldom necessary.none of these large turbos are cranked out at 2000 rpms.also the factory gn tv spring is too short for most applications that need over 140 psi line (or in reality approximately 15% of the amount of the 90 psi fed to the plunger by the tv limit valve that is regulated out into the modulated tv oil circuit)just above minimum throttle or 2000rpms.as for the lock up point it is to be determined by jumping the aldl at the track to find the best et and mph and then programming it into the chip.these things are simple if you use my tech,there is no sense in throwing other variables in to make yourself cofused,leave that to those who dont have time for anything better to do

 

[chris718]

also the statement about vaccuum reference being more accurate than the cable is simply not true,the cable will max out line at wot .the vaccuum system uses a pressure cutback on a 2/3 shift by sending oil to the modulator valve to bias it toward the low pressure position.simply viewing the gm schematics will validate this information.the cable system uses the tv limit,tv plunger,line bias and orifice sizes to map out a proper line rise strategy,much more intricate and better performing than the vaccum system.high vaccuum and high torque output are common with large engines(non turbo),hence the high gear problems that plagued ost th 350 and th 400 units before the research was done to find a solution.also the vaccuum system is very poor with turbo applications which is why we use the cable pulled modulator with street th 350 and 400s used with the turbo.abnormal shift scheduling is the result of turbo with vaccuum modulator

 

[Alky V6]

in my opinion 300 psi at 45 degrees of throttle angle or half throttle is insane.with our tech and the dual feed in high gear there is actually way over 1000 psi applying and holding the direct clutch.if you simply go on a dyno to view your torque curve you can size the modulated tv oil hole in the plate to properly ramp oil psi in relation to torque.also like ive been saying all along the use of the mcss valve body or its longer tv plunger spring.sizing up to .080"can be used for instant ramp up but this is very seldom necessary.none of these large turbos are cranked out at 2000 rpms.also the factory gn tv spring is too short for most applications that need over 140 psi line (or in reality approximately 15% of the amount of the 90 psi fed to the plunger by the tv limit valve that is regulated out into the modulated tv oil circuit)just above minimum throttle or 2000rpms.as for the lock up point it is to be determined by jumping the aldl at the track to find the best et and mph and then programming it into the chip.these things are simple if you use my tech,there is no sense in throwing other variables in to make yourself cofused,leave that to those who dont have time for anything better to do

Since I don't have time for anything better to do and some people find this interaction helpful, why don't we all keep exploring this subject anyway, so other people with little knowledge on the subject can get a good understanding of TCC clutch durability problems that can come about from the different torque converter designs that are out there in the market.

I find it very commendable that Chris dynos every engine/transmission combination so that line pressure rise will match the individual torque rises from different engine/turbo combinations so that unnecessary friction element damage is avoided. Very well done. And really, that is the only correct way to do it. How much extra is charged for this service? On the flip side, most transmission shops can't afford an engine dyno, so the option is to find a line pressure rise that will fit all, but the most extreme cases out there, and maybe even those if you know what the case is. I contend that the same care in making sure that the friction elements have proper piston surface area, friction plate surface area and line pressure rise be used in selecting a TCC lockup stadegy for each type of torque converter out there in the market. For instance, you would not use the method described by Chris when using an OEM torque converter. At least, I would hope you don't, unless you like replacing torque converters.

To defend the use of 300 psi line pressure. My own experience has shown that in extreme cases (over 700 HP), even with dual feed, that pressure is necessary to ensure an acceptable life from the high/rev clutch pack. I commend Chris for finding a different way.

 

[Grumpy]

ok lookin at posts here ... back to the original posts .. I have been running stock D5s in all my fleet of Buicks and TTAs ... lock them at the line .. stockers with a good stator support with AC shift kits and of course a good "cooler" . never ate a clutch in the converter ..and we drive with a switch by our side . I think its the best thing Buick ever did . these are only mid 11 street cars . oh one thing we are good at is breaking the forward drum Chris is sending me one to try :biggrin: right Chris