geckonz08

could someone please explain the desirability (necessity?}of having different sized tq's ??
cheers
mike

droptopron

Generally speaking, the smaller the converter the higher the stall.

joe_padavano

The basic principle is what stall speed do you want/need for your application? The stall speed is the RPM level where the engine will start to stall out if you apply the gas while holding the brakes with the trans in gear. Normally you would only do this at the starting line of a drag strip to improve your launch and thus reduce quarter mile times. The trick is to match the stall speed to the torque and HP curves of the engine. The smaller converters will have a higher stall speed, which might be an advantage depending on cam and engine configuration. The problem is that the higher the stall speed, the more the converter will slip in normal use, resulting in higher revving to start off, higher trans fluid temps, and worse gas mileage. If you have a relatively stock engine and don't plan to regularly drag race the car, you want a near-stock converter diameter and stall speed.