The Right Torque Converter Can Make The Difference Between Winning And Spinning Your Wheels
Today's performance world offers plenty of ways to make big power, and selecting the right converter to transfer that horsepower efficiently can be challenging.Simply said, without the right torque con-verter, you may very well be giving up precious e.t. and mph at the dragstip.
It's no secret: Torque converters can reek of voodoo science, especially since everyone seems to have his own idea of what works and what doesn't. So that you don't have to play guessing games and spend your hard-earned greenbacks on your buddies' theories, we went directly to a number of leading torque converter manufacturers to learn what's involved in choosing the right converter. We also spent lots of time on the phone with key gurus, who shared valuable insight when it came to tips and tricks for hard launches and maximizing the power you already have.
Terms & Functions
Coupling efficiency:
The actual speed ratio, the turbine shaft rpm divided by the pump shaft rpm.
Stall speed:
The maximum engine rpm at which the engine transfers power to the transmission with the vehicle's brakes applied or a transbrake activated.
Torque multiplication:
The torque converter's ability to multiply torque, which will affect the vehicle's initial acceleration.
4 Main Components
Cover (A):
The outside half of the converter housing positioned toward the engine side.
Pump Impeller (B):
The outside half of the converter positioned on the transmission side. Inside is a series of longitudinal fins, to move the fluid around its outside diameter into the turbine. The impeller and cover are welded together and the cover side is bolted to the flywheel.
Stator (C):
The component that redirects oil flow between the turbine and pump. This is also the part that makes a torque converter a multiplier and not just a fluid coupler.
Turbine (D):
Moves within the cover and is attached to the drivetrain mounted on a spline fit to the transmission's input shaft. As the turbine moves, the vehicle moves.
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The torque converter's overall diameter contributes to how much stall speed and efficiency the converter has. Generally, smaller torque converters offer higher amounts of stall speed than larger ones. The torque converter on the right is a stock 12-inch with about 1,500 stall speed, and the one on the left is an aftermarket 10-inch converter rated at 2,800-3,000 stall speed. The actual stall speed, though, would depend on many variables, including the engine's torque level and the camshaft's powerband. | 
Furnace brazing strengthens a converter by causing the housing and fins to move and act as one. This minimizes flex and increases durability. The added rigidity keeps the fins' shape more consistent under pressure so the converter performs better. The turbine on the right has been furnace brazed and the one on the left has not. |