How can a 12″ torque converter and a 9.5″ torque converter both achieve the same stall speed?
Two different sized converters can have the same stall speed, but the efficiencies will vary greatly. A converter pump will tend to have a higher efficiency when its blades have a positive angle to them. The positive angle feeds the most amount of fluid to the turbine. The more fluid you feed the turbine, the harder it pushes on it. The harder the turbine is pushed, the more torque is transferred to the transmission. For a 12″ converter that normally stalls at 1600, to be converted to a 2600 stall, most converter builders will bend the pump blades back to a negative angle to feed less fluid to the turbine. This means the pump will have to turn more rpms to force the turbine with the same amount of fluid as before. As you can imagine, the efficiency starts to drop off rapidly as you bend the blades more and more negative. You will lose rwhp. A 9.5″ converter stalls higher because it generates less fluid by virtue of it’s smaller size. It takes more stall to achieve the same amount of hy
