You A-4 drag guys talk a lot about high stall speed torque converters for your A-4s as a key to winning times. As an M6 guy, explain the whys and wherefores of the torque converter upgrade to me. Thanks.

 

Think of being able to add about 3 more gears to your M6 in place of first gear (w/o the added shifting time)and keeping the engine always in the powerband.

That is the advantage of a highstall torque converter and its torque multiplication curve.

 

Using a stall converter is like dumping the clutch at ~3000rpm instead of ~2000rpm, which obviously has the motor up more in its powerband.

The factory converter stall speed is between 1600-1800rpm, which means when you step on it, at ~1800rpm, the converter will lock (same as clutch grabbing) and you're going. Some converters stall as high as 4000-4500rpm, which require major traction mods, as well as engine mods (to run at high rpm's) but they'll really let the engine scream before it launches the car!!

 

Stall alone isn't worth the hassle. Once you have a converter that stalls at 3600 but due to a defect gives no torque multiplication, you quickly realize that stall ain't where its at. It is the proper stall to put you near the optimal portion of the torque curve but the proper torque multiplication to take car of you before you get to that portion of the torque curve.

 

translated into grade 4 level english, you just said what?!

If I heard you right, you're saying that you can't just buy any TC and expect it to give you optimum performance --- you have to choose one that's gonna work well with the engine you've got and the torque curve of that motor??

I think that's what you meant!

 

Yeah, simply put you want your stall speed to be around the peak torque of your motor.

 

Noper that is only half of the situation.

You have two major things that have to be considered when buying a torque converter:

1) Stall speed
2) Torque Multiplier


Two converters at the same stall speed can have completely different power profiles and feel.

I think Yank has some explaination and graphs at how the torque multiplier/STR makes a big difference. checkout www.converter.cc

 

Thanks Luna, I stand corrected. I guess you do learn something new everyday.

 

Thanks for the posts and the link. This torque converter tech is much clearer now.

I assume that the computerized, automatic clutch manuals, like the rigs on the Ferrari 360 and BMW M3 SMG, to name a few, will ultimately make automatics obsolete for sporting applications, either drag race or road race. The ability to pick RPM and launch priorities--speed v. smoothness, etc., and let the computer optimize the process, will surely lower everyone's E.T., as well as improve road racing--no missed shifts, no overevs, no problem matching revs on downshifts.

 

I personally believe that the CVT is the future once high torque ratings can be utilized.

 

You may be right, Luna, about the CVTs, but for now they seem very fragile--too many belts and chains, etc., but perhaps that can be corrected.