High Stall Torque Converters

Craig S. · 06-22-2009, 05:35 PM

Anyone tried a higher stall T.C. in their later model 4 speed autos, for quicker 0-60 times? 928s can be quick, as well as have an awesome top end.

Danglerb · 06-22-2009, 07:48 PM

One of the Rennlist guys, Zeus+ was talking about doing a TC stall upgrade, but I don't know if he got around to it.

Falls into my category of one of the last things to change, not because of merit, but to match the final characteristics of any other changes.

I'm not sure of what the downside to higher stall is, guessing drivability and mpg.

Dozman · 06-22-2009, 10:31 PM

Have heard some guys who have used the non oem converters, complain of vibrations from them at certain rpms. You would have to check the other forum for further facts, and if they were solved.

Craig S. · 06-23-2009, 05:55 PM

Quote:

Originally Posted by Danglerb

One of the Rennlist guys, Zeus+ was talking about doing a TC stall upgrade, but I don't know if he got around to it.

Falls into my category of one of the last things to change, not because of merit, but to match the final characteristics of any other changes.

I'm not sure of what the downside to higher stall is, guessing drivability and mpg.

I agree Danglerb, with matching other changes to the car.

My 928 has an extra 100 H.P. over a stock S4, mostly thru intake an exhaust work.
Gt cams, Ott X pipe, 2.5 dual exhaust with high flow cats, 968 intake valves, port matching, Autothorty chip, rising rate fuel pressure reg... a healthy N.A. engine.
All this work was done by the prior owner who also had an 2400 RPM stall T.C. With this setup the car could run mid 4's 0-60. The car now has a stock T.C.
with a beefed up transmission. Somehow the 2400 T.C. got left out on the trans. rebuild.
Anyway I am thinking of getting the 2400 stall back since I can only now manage mid 5's 0-60. Smoking 285/30 18's gets expensive but mid 4's 0-60 is a rarity for a 20 year old car. This engine with the GT cams likes high revs.

Craig S. · 06-23-2009, 06:04 PM

Quote:

Originally Posted by Danglerb

One of the Rennlist guys, Zeus+ was talking about doing a TC stall upgrade, but I don't know if he got around to it.

Falls into my category of one of the last things to change, not because of merit, but to match the final characteristics of any other changes.

I'm not sure of what the downside to higher stall is, guessing drivability and mpg.

I agree Danglerb, match the other changes.

Car is 100+ hp over stock S4 with N.A. Has run mid 4's 0-60 with 2400 RPM stall.
With stock T.C. now only mid 5's... thinking of going back. Mid 4's is rare company for a 20 year old car.

Craig S. · 06-23-2009, 06:09 PM

Sorry for the multiple posts... I had log in problems

Danglerb · 06-23-2009, 07:42 PM

I am amazed you have traction with a hard launch as it is, what final drive ratio are you running (do you know model number of tranny for 1st and 2nd gear ratios?)?

And I am officially jealous.

Its a fine point in tuning how you want it to launch, pick your tires etc. and set the stall to optimum boat floating.

Do you have any trouble with wheel hop when the tires hook up?

Craig S. · 06-23-2009, 08:54 PM

As far as I know the trans. is an A28/16 4 speed auto with the 40% M220 LSD.

Prior owner blew up 2 transmissions... Latest one has AMG hardened planetaries, special clutches, Amsoil synthetic fluid. Need those revs. that this motor likes to get the tires smoking and most C-5 Vetts wondering what happened.

Danglerb · 06-23-2009, 10:47 PM

A very nice page of specs ....

http://members.rennlist.com/pirtle/s4atrans.htm

Edited ***
Ratios A28/16 A28/the rest
1st gear 3.87 3.676
2nd gear 2.25 2.4120
3rd gear 1.44 1.436
4th gear 1.00 1.00
Reverse gear 5.59 5.139

Final drive ratio
15:33 i = 2.200
14:33 i = 2.357 (A 28.05/08)
13:33 i = 2.538 (A 28.06/09/11/14/16)

Stall speed
A 28.04/07 = 1650…2050 1/min
A 28.05/06/08/09/11 = 2200…2600 1/min
A 28.12 = 1750…2150 1/min
A 28.14/16 = 1750…2150 1/min

***************

Have you checked the current stall speed?

I wonder if you could use the earlier higher stall converter?

Craig S. · 06-24-2009, 03:54 PM

Quote:

Originally Posted by Danglerb

I am amazed you have traction with a hard launch as it is, what final drive ratio are you running (do you know model number of tranny for 1st and 2nd gear ratios?)?

And I am officially jealous.

Its a fine point in tuning how you want it to launch, pick your tires etc. and set the stall to optimum boat floating.

Do you have any trouble with wheel hop when the tires hook up?

Thanks for the specs. on the transmission. I don't have wheel hop... I think more of a manual trans. thing.

Another tuning gem this motor has going for it is, the GT cams are indexed + 3 degrees, which helps with a early onset of torque and more of it down low, but there is still big power on the top end.

EIPtuningR32 · EIPtuningR32's Garage

Quote:

Originally Posted by Craig S.

Anyone tried a higher stall T.C. in their later model 4 speed autos, for quicker 0-60 times? 928s can be quick, as well as have an awesome top end.

i have one on my t-bucket. let me tell you what a PITA it is to try to drive sensibly. you try to take off from a red light like a normal car and you cant because it wont engage the clutch until (in my case) 3500 rpm. then, depending upon how much throttle you are using, it either eases in the clutch, or it pops the clutch and you lurch forward.

123quattro · 06-25-2009, 12:02 PM

High stall converters without the lockup feature also really heat up the trans fluid. I don't have an auto 928 so I'm not sure if they can lock the converter. I'd guess no.

rhjames · rhjames's Garage

depending on how loose of a converter you want (2500, 2500, 4000, and up stall speeds), you'll have heating issues and extreme slippage to deal with. Just remember that you're basically dealing with a small block (engine) and a heavy car. A typical converter for this application would be a 10 inch converter for street use.....upwards of a 7 or 8 inch converter for serious drag racing. Big block engines typically flash higher stall speeds than small block engine.

However.....once you get to the point of playing drag racer with the 928, the rear suspension becomes the limiting factor. There's nothing back there to limit wheel hop, broken axles, suspension pcs pulling away from the sheetmetal attachment points, etc.....

if you really want to push the envelope, a trans brake would be next, with a reverse pattern shift.

You might send an inquiry to John Winters (Rockledge, FLA). He is the guy for powerglide trannies in the drag racing community, and may possibly be able to use that technology to build you a converter using the OEM unit as a model. I would imagine the only parts he would need are the front hub and internal drive spines for the input shaft of the tranny. He has a website (JWPerformance or something like that) or you can find his ad in most drag racing publications.....

--Russ

Danglerb · 06-26-2009, 04:42 PM

As far as I know the the torque converter is a 100% MB part, used in various MB models and with several options within those models for stall speed etc. I think all of the pre 87 Euro AT used a 2400 rpm stall vs 1950 for USA models.

Craig S. · 06-26-2009, 05:54 PM

Thanks for all the input ya all.

My car has been thru a lot of testing regarding this matching of torque converters.
The prior owner had a well matched unit, blew up a second transmission, finally got someone who knows these MB trannies to build one that would hold up, and the zoomy TQ went to the dump somehow with the blown tranny!
Anyway Edge Racing Converters in Simi Valley, Ca. built the custom 2400 rpm stall that worked for my engine a few years ago and I hope they can reproduce what was in there.

I'm after max performance with reasonable street manors. With a stock TC the car is a missile once it get rolling and the revs are above 3000 rpm.