What is the proper method for checking the stall speed of a torque convertor?

[GNVAIR]

As posted above? I know boost makes a difference in stall speed ratings as well. How should it be done and at how many pounds of boost......if any?

 

[turbot2112]

i was told to put the trans in drive, foot on the brake and on the gas until your creeping.

 

[mgmshar]

This discussion came up on GNTTYPE a while back. I believe the consensus was to check stall speed by hitting the brakes and applying throttle until the boost is right at zero psi (i.e. not vacuum and not boosted).

Anyone else remember this?

 

[turbot2112]

acyually i was told keep it in second gear.

 

[OneLethal87GN]

I think the old way of holding the brake while bringing up the rpms doesn't always work. This is in part due to worn brakes or worn tires and such. I believe the only sure way is to have a tranny shop test it.

 

[billsgn]

I wonder when the tranmission experts are going to respond???

 

[chris718]

the proper way to check stall speed for a given application is very simple .stall speed is the maximun attainable engine rpm that can be reached w/the car in gear at wide open throttle and the brakes or trans brake applied and the rear wheels stationary i.e. wheels not turning .stall speed will vary from car to car with the same engine and transmission depending on rear brake condition/quality/adjustment/and tire condition/compound and quality.a trans brake will allow maximum stall speed because there is no energy in the driveshaft like when you are footbraking .when footbraking you can only attain a certain rpm before the mechanical leverage available overpowers the vehicles brake system.the same car when tested w/the foot brake and transbrake method will yield between 300 to 700 rpm more stall speed when the engine is loaded against the transmission brake.www.ckperformance.com.....check out the site.

 

[ChrisCairns]

Originally posted by mgmshar
This discussion came up on GNTTYPE a while back. I believe the consensus was to check stall speed by hitting the brakes and applying throttle until the boost is right at zero psi (i.e. not vacuum and not boosted).

Anyone else remember this?

I remember that and still use it. I believe that suggestion first came from PTE. And it's not perfect but it's all we turbo guys have to compare one converter to another.

With our cars we can easily "drive over" the converter. What stalls at 3000 in an NA car can simply keep going up in rpm as more horsepower (boost) is applied.

 

[chris718]

i believe my method should prove worthwhile for checking stall speed.when selecting a convertor based on engine torque i like to go on the low side with a turbo motor because of the increased flash stall speed .as far asd 0 boost that in my opinion is nonsense because in the real world who is launching with 0 boost.?every car responds differently to identical convertors depending on induction,rear ratio ,tire size,brake adjustment and holding power, exhaust system efficiency ,engine torque ,temperature,vehicle weight,t brake camshaft,lifter type ,the list goes on.this is a lesson on how to check stall speed of a convertor as installed in a vehicle ,selection however is a whole different ballgame.www.ckperformance.com

 

[ChrisCairns]

Originally posted by chris718
i.as far asd 0 boost that in my opinion is nonsense because in the real world who is launching with 0 boost.?

Using zero boost gives a comparison of converters. Otherwise where is the relative point??

For instance at zero boost the converter stalls at 3000 rpm...then incease boost to 10 psi and it stalls at 3600...then increase boost to 20 psi and it stalls at 4200 rpm what stall would you call that converter??

And we can drive over the conveter very easily once we use a brake compared to foot braking. How would you compare that same converter since it's effective stall speed is raised but the converter remains the same??

 

[S10xGN]

Originally posted by ChrisCairns
Using zero boost gives a comparison of converters. Otherwise where is the relative point??

Chris,

I don't think you could ever compare converters to a "standard" measure. A given converter will stall differently on different engines - sorry, that's just the way life is. If you put a "2500" stall converter on a 305 smog motor, it might stall at 1700, put it behind a 502 crate motor and you might see 3300. Same converter; different stall speeds on differently built engines. I remember this thread from several years back, but your trying to "standardize" something that cannot be held to a standard. I'd follow CK's procedure to check *your* stall on *your* converter behind *your*engine in *your*car, becuse it'll be different in any other combination.

 

[ChrisCairns]

We're in agreement Russ. As you know, the reason that the same converter will stall differently between a 305 and a BB is torque. And that's what I'm saying. You add torque (boost) and the same converter has a higher stall.

The zero boost isn't a perfect method but it's the best one for turbo cars in my opinion.

 

[GNVAIR]

The one I was sold is supposed to be a 3500 stall. At 0 psi it stalled at 2850. Maybe Bruce could lend his opion?

 

[chris718]

thanks guys ,im glad some of you undestand the information i post and appeciate it.www.ckperformance.com

 

[WE4]

This is truth..

Originally posted by chris718
i believe my method should prove worthwhile for checking stall speed.when selecting a convertor based on engine torque i like to go on the low side with a turbo motor because of the increased flash stall speed .as far asd 0 boost that in my opinion is nonsense because in the real world who is launching with 0 boost.?every car responds differently to identical convertors depending on induction,rear ratio ,tire size,brake adjustment and holding power, exhaust system efficiency ,engine torque ,temperature,vehicle weight,t brake camshaft,lifter type ,the list goes on.this is a lesson on how to check stall speed of a convertor as installed in a vehicle ,selection however is a whole different ballgame

I agree with this ......


And you either like it and it works well or it/you do not.
How does the CAR like it Lee?

 

[FastTurb]

I'm sure I'll get blasted for this but with some previous vehicles I used to load them up against a secure 4X4, raise the rpm and the car would sit, sit sit and then bing climb over the 4X4. I used to think this was my stall. Now I never tried to find the "flash" stall this way because it could be dangerous. the slower rpm bumping allowed me to get it out of it as soon as the car started jumping the 4X4 and not break anything or hurt anyone

I'm sure the experts can explain how bad this is....

 

[GNVAIR]

Bruce, it seems a little soft off the line leaving with no boost. That was why I question what the proper technique for testing is.
We see and hear people saying they have for examples.....a 3200 stall Vigilante or Art Carr or Pro Torque or 9x11, but there doesnt seem to be a consistant published method of testing for stall speed.
On my car I have found this:
0psi = 2850 rpms
10psi = 3500 rpms
15psi = 4200 rpms
My convertor was supposed to be a 3500 stall. Does this mean that the standard for rating them is at 10lbs of boost? I dont understand that was why I asked the question.

 

[WE4]

And... a tough explanation it is..

How does the lag feel? Can you hold 15 lbs with brakes? Did it "wake" up the car? I understand why you asked the ? and am trying my best to answer it. How is it from a rol? Does it feel lazy?
How is the "drivability"?

Bruce
WE4

 

[GNVAIR]

Yes, I can hold 15lbs with the brakes. On my Scanmaster it will be at 4200 rpms when the boost is at 15lbs on the brakes. It feels pretty good. It just takes a second or two for the boost to come on when flooring it from a stop in first gear. I guess I am comparing it to the TA49/D5 convertor I had before. Its definitely livable, so please dont take it as derrogatory.
I am just curious what the industry standard is for measuring boost. No one has ever stated that on here. When someone sells a custom 3500 stall convertor, it would be nice to know where and how it is supposed to stall.

 

[S10xGN]

Originally posted by GNVAIR
I am just curious what the industry standard is for measuring boost. No one has ever stated that on here. When someone sells a custom 3500 stall convertor, it would be nice to know where and how it is supposed to stall.

Lee, I think the point is - THERE IS NO INDUSTRY STANDARD! For a "custom" 3500 stall converter, the maker will look closely at YOUR combo, and make a [very] educated guess at what needs to be done inside the converter to make it stall at 3500 (foot to the floor with brakes on) in YOUR particular car.