With all the stall speeds available many people in our market ask "What stall speed is the best". In short, there is no best, it's about matching your needs to the right unit.

The next question, we get is "what does that stall speed number mean?” Specifically in our market, not much. ZZP and the other vendors in our market label converters whatever we want. ZZP based our labels on what people had come to expect the numbers to mean. In other words, there is no technical explanation for the labels on our converters. Because of this you may get some very strange responses from people not familiar with our market. "OMG, you can't run a stall that high!" or "That's not enough converter (referring to the stall speed not being high enough". Both of these responses are common by mechanics not familiar with our market. Neither means anything because they aren't familiar with our rating system.

The technical explanation for stall speed is the amount of difference between the engine speed and transmission speed. But the problem with specific ratings is that, the stall speed changes based on the weight of the vehicle, speed of the transmission and most importantly, horsepower of the engine.

Higher stall converters allow better launches and more low end grunt because the engine can get higher into the power band while the transmission is still or at a lower speed. The sacrifice is in top end horsepower, gas mileage and heat. Below is a dyno of a maxed out M90 setup with and without the converter locked. It's a ZZP 3500 stall converter. As you can see there is a lot of low end power gained by letting the converter slip but there is also a large penalty up top. On our 2500 stall converter the two lines wouldn't be separated so far. We normally see only about 10HP lost up top. Because the 3800 with an M90 makes so much torque, we generally recommend our 2500 stall converter because more power at launch is not going to help as much as more top end power.