[tech] Choosing the right Converter Explained
 

Article by: Walt Vengelis Jr.
December 2002

High Stall Speed Torque Converters
For performance applications, a "high stall speed" torque converter may be just the thing. A higher stall speed torque converter raises the engine RPM at which the vehicle launches. In other words, it increases the engine speed which is necessary to lockup the converter and launch the vehicle. The benefit of doing this is that it multiplies off the line torque for faster acceleration.

For performance, the torque converter should reach its stall speed at the same time the engine hits its peak torque output. The heavier the vehicle, the more it will benefit from a higher stall speed. But there's a drawback.

Installing a torque converter with a higher stall speed also means the engine is going to rev up a lot higher before the vehicle takes off. For everyday driving, this can be rather annoying as well as murder on fuel economy.

Types of Torque Converters:

Street Converters
Street/Strip Converters
Race Converters
Off-Road Converters
Towing Converters

The typical street customer is looking for better off-the-line acceleration . The type of torque converter that's best for this type of application is probably a 10- or 11-inch medium-duty unit with a stall speed 200 to 500 rpm higher than stock.

The street/strip customer wants the best of both worlds, and may be willing to sacrifice some everyday drivability in order to blow the doors off the competition when things get serious. An un-blown small block V8 or a slightly modified big block V8, a medium- to heavy-duty converter that offers stall speeds 800 to 1,200 rpm higher than stock would probably work best. For a blown engine or a really healthy big block, a beefed-up converter with a stall speed 1,000 to 1,500 rpm higher than stock will provide the necessary punch.

For the serious drag racer, the sky's the limit. Race converters come in 8-, 9-, and 10-inch sizes. A typical race converter is built to withstand high torque loads and stall speeds up to 5,000 rpm or higher. They're great on the strip, but impractical for everyday driving.

Off-road trucks usually have large displacement V8s that are built for low rpm torque. A high speed torque converter would be impractical in such applications so stick with a unit that offers an increase in torque multiplication below 2,000 rpm, but has only a slightly higher than stock stall speed.

For someone who's towing his speed boat or race car behind his pickup, a torque converter that allows a little more slip than stock (say 200 to 300 rpm more than stock) is the best choice. And for someone who drives with one eye on the gas gauge and wants to wring more miles-per-gallon out of his buggy, an "economy" converter that offers increased efficiency and/or lockup capability is often the best option.

One other thing to keep in mind: torque converters generate about 95 percent of the heat inside an automatic transmission. Raising the stall speed increases friction and heat, so an auxiliary transmission cooler must also be installed to keep fluid temperatures under control.

When choosing a converter, your best bet is to contact one of the reputable converter manufacturers for your application.
Now that you have a bit more information on the use of different types of converters, we hope you'll be more educated in choosing one!