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Original Message
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| RE: Need more specs |
| By Travis Miller - 01/20/2002 10:11:07 AM; IP 205.188.192.173 |
High stall convertors are needed for cars with big rumpity-rump (large duration) type cams that need to idle high. The stock convertor usually does not have enough stall and the engine dies when the automatic trans is put in gear. High stall convertors are also great for hard takeoffs such as on the dragstrip. The convertor allows the engine to rev to a higher RPM before it catches and launches the car. But all of this has a tradeoff.
If the car sees much street driving, the convertor will be slipping unless the engine operates in a range above the stall speed. In other words the car will feel "mushy" when driving until the stall speed is reached. A lot of people, after installing a high stall convertor in their street car, miss that old crisp feeling when the throttle is quickly opened as the car is running along at speed. This is where planning ahead comes into place. There are math formilas that can be used to determine lots of items on a car. One is MPH vs RPM vs gear ratio vs tire diameter. This and other good math formulas can be found at www.prestage.com in the car math section. They have a simply fill in the blanks format for the formulas.
Using the example posted in this thread, 3.50 gears with 26 inch tall tires at 60 MPH calculates to 2714 RPMs. That means if you install a 3500 convertor, at 60 MPH the convertor would pull the car but it would still be trying to slip, hence the "mushy" feeling. Around town you do not drive 60 MPH on the side streets. High stall convertors are for the dragstrip unless you want to run a very low rear gear and keep the engine at higher revs all the time. In that case, do not plan on a very long road trip. |
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