torque converter sizing

[bigTomHanks]

How do manufacturers size torque converters for a particular vehicle? Do they do a trial and error until they get the characteristics they are looking for or are torque converters given classifications that can be used to size them for a particular vehicle weight, torque, etc? I'm trying to size one for my applications and am having a hard time selecting the correct one that will give them the characteristics I am looking for with any confidence.

 

[MikeHalloran]

ISTR that the primary parameter used is 'stall speed', i.e., the input RPM where input torque and output torque (at zero speed) are the same. I also STR that it varies with the fifth power of diameter, so even a visually indistinct change can make a big difference in performance.

I remember one really low-buck hotrodder who replaced a 283 Chevy with a 348 Chevy in a rapidly aging Impala, back when that was a big car. To soup it up, he used the 283's converter behind the 348. I think the difference in converter OD was on the order of two inches, which is really quite a lot in converterland. The kid was hooning it around for about two weeks before he broke a rear axle control arm bolt or something like that. With the too-small converter, the big engine would spin up fast enough and far enough to annoy the neighbors, even when he wasn't trying to.







Mike Halloran
Pembroke Pines, FL, USA

 

[TheBlacksmith]

I'm pretty sure aftermarket manufacturers have programs to determine this, engine size, cam/power range, weight, gear ratio, etc. would all be entering arguments.