I was kind of looking at this as I was driving around tonight. Doing what Kent suggested and watching the tach as I took off I really couldn't get a consistent result. Once it seemed like it took off just above ~550 idle and another it seemed to be closer to 1,000-1,100.

If there is a more consistent way to check post it up and I can try too.

 

I would definatly appreciate the feedback for anyone that would like to test! Data is needed for both the 955 and 957 turbo models.

Seems like the footbrake method with application of the parking brake would help to keep the vehicle stationary. I also read that chocking the wheels could help however I would advise to really pay attention and not brake boost for more than three seconds twice in a row. I did find some published advice on checking stall and post it here.

"There are three common methods to gauge the stall speed characteristics of a torque converter. Footbrake stall is the maximum amount of engine RPM that can be achieved in a forward operating range with the brakes fully applied to prevent the vehicle from moving forward. Footbrake stall is not an accurate method of determining the true maximum stall speed of a torque converter. Furthermore, advertised stall speed ratings are not based on footbrake stall speed. Maximum static stall is the maximum amount of engine RPM that can be achieved in a forward operating range without generating any driveshaft motion. Maximum static stall can only be verified in a transbrake-equipped vehicle. Flash stall is the amount of engine RPM (or flash) that is observed upon initial acceleration under load. The easiest method for checking flash stall is to drive the vehicle at low speed in second or third range and immediately transition to wide open throttle. The RPM level that the engine immediately accelerates to is the flash stall. Flash stall speed is one of the most useful ways to truly gauge the stall speed characteristics of a torque converter and how those characteristics will influence the acceleration potential of a vehicle."

Many thanks in advance:-)

 

I'll try some of that. I have some driving around to do tonight.

 

Well, I'm not sure what they meant by driving in low and stomping on it. It just downshifts and the rpm's shoot up quick? Unless they are talking about being in manual mode and doing that. I will try that here in a bit, have one more errand to run.

There seems to be a bit more info about stall speed here. Not sure brake stall is going to do any good and not sure I can reliably catch the real stall speed when cranking from a stop. But I'll take a look.

http://www.converter.com/faqs.htm#stall2

 

Yes, I think manual mode, 2nd gear from a stop would be good.

 

I tried that with light throttle, full throttle, rolling a bit then rolling on the throttle. I have no idea but I suppose my best guess is that it seems like it's probably pretty low like 950rpm?

Even with the digital P3 gauge I have it's almost impossible to catch when the car actually starts moving because it just takes off and spins up so quick.

 

Here's my data:


Using the brakes and the e-brake with the front wheels chocked, then going full throttle it would immediately jump to around 2000 rpm. Within a couple of seconds, boost would begin to build and it would climb to 2400 rpm and maxing out slightly past the .4 bar mark on the factory gauge. Tried again without the wheels chocked and it does the same thing.


From a dead stop, no brakes applied, 2nd gear, it moves pretty much instantly.


From a walking pace, 2nd gear, full throttle, the rpm jumps immediately to approx. 1500 rpm before there is a change in speed, but this happens very fast, less than a second. From as slow as 3rd gear allows, full throttle, it jumps to around 1800 rpm immediately.


If you need more exact data, I'll do it again with the durametric set up, just let me know what needs to be set to log. I have never used the logging function on the software before.


My car is a 05 Turbo, 176k miles, stock except for secondary bypass.

 

This is exactly what I needed and I don't think the data will get much better without a transbrake. The stall characteristics seem to be in line with the factory specified stall of 2742rpm. On a side note, the factory TC seems to be pretty tight. That is a whole nother' subject as TC's can be setup tight or loose. I do not own a Durametric yet so I would have no clue with that.

Thanks a million for your help!

 

Happy to be of assistance. I agree that the factory TC seems to be tight. Its been quite a while since I read up on converters, but I believe that has something to do with the STR? So many variables in transmission setup.


Do you have a plan for yours or are you going to see how it goes with the factory stall?

 

I am definitely going to have it beefed up/rebuilt. I think I will talk to the shop and see how loose I can expect it to be with a 500 rpm stall change. In reality, anything more than 3250rpm would not be as street friendly, even with a lockup converter. From what I read a TC is supposed to stall @ or slightly above peak TQ. Peak TQ on a stock 955 is 2250rpm. Makes sense. The turbo's I will be using will be much larger than stock, however, they have a lot of attributes that should make them spool much much faster than a similarly sized journal bearing unit. Plus, I'm doing a bunch of other mods that will affect the final outcome. It is a tough choice.

Once again, thanks for your help!