General Torque Converter Questions...

[comradburk]

I just had some questions about torque converters... I understand how they work, and that the stall speed is the speed at which the two parts (turbine and pump i believe) spin at almost exactly the same speed and the stator is just kinda spinning freely (right??), so why exactly does it help to have a larger stall torque converter on a car with more horsepower?? and why does a larger stall converter help the turbo spool better??

 

[ijames]

Often, a high hp motor gets there by using a camshaft that does not let the motor make much torque at low rpms, and a big turbo that takes much more exhaust flow to spool up than the stock turbo. The higher stall speed lets the motor rpm rise higher (by definition ) before the converter stops letting it rise (at which point the only way the rpms can rise further is to accelerate the car). This lets the motor flow more air, which makes more exhaust, which spins the turbo up faster. A looser converter also lets the motor rpm quickly get up to where that big cam can make some power. Put those together and a motor that may make twice the hp of the stock motor at 5000 rpm may make half the hp of the stock motor at 1500-2000 rpm, and with a tight 2000 stall converter would actually be much slower than the stock motor from say 2000-3500 rpm. Above 3500 the higher hp motor would win, so something like a 3000 stall converter lets the big motor get past that weak spot and into its powerband quickly.

 

[comradburk]

Ahhhhh. I always knew you needed a higer stall converter with a high hp motor, but I never knew why exactly. Thanks.