Torque Converter
#1
10-16-2006, 02:16 AM
Torque Converter
My friend just bought an 83 Z28 with a 3 week old paint job. It has a 305 with the 4 speed automatic. What's a good brand of torque converter that doesn't cost too much? And how much?
#2
10-16-2006, 02:21 AM
RE: Torque Converter
What stall speed are you looking for?
http://store.summitracing.com/egnsea...47&D=%2D101847
http://store.summitracing.com/egnsea...47&D=%2D101847
#4
10-16-2006, 05:46 PM
RE: Torque Converter
http://www.nhra.com/dragster/1999/is...echnology.html
"One size doesn't fit all when it comes to torque converters. What's the bottom line? Contact manufacturers directly for an exact recommendation based on your combination. Remember to provide accurate information about your own combination. If you fudge the numbers, you'll end up with the wrong converter, and you won't be happy. That's one thing that can be guaranteed."
"One size doesn't fit all when it comes to torque converters. What's the bottom line? Contact manufacturers directly for an exact recommendation based on your combination. Remember to provide accurate information about your own combination. If you fudge the numbers, you'll end up with the wrong converter, and you won't be happy. That's one thing that can be guaranteed."
#5
10-16-2006, 07:12 PM
RE: Torque Converter
Stall speed is the RPMs where the converter has fully locked and there's no slip. The higher the stall speed, the higher you can rev the engine at launch. You'll want something with a stall speed that compliments the power band you're running. The higher you hit peak torque, the higher you'll want your stall speed to be. I have a 2500 in my mostly stock LO3+700R4 combo, and it seems to work pretty well, but as Norm said, call up a manufacturer and ask what they reccomend.
#7
10-17-2006, 02:56 PM
RE: Torque Converter
Stall speed is not just a function of the converter. It is also a function of engine torque. This can be relatively easily described by defining the "K" factor. K is simply the constant in the equation K = rpm/sqrt{torque}. The equation describes the observed behavior of the converter behind a specific engine. What this allows us to do is determine what the stall speed of a given converter will be if we put it behind a different engine.
For example, if a motor has 400 ft-lbs. of torque and stalls a particular converter at 3,000rpm, K = 3,000/sqrt{400} = 150. Since we know K = 150, we can predict the new stall speed if torque is increased to say 500 ft-lbs by rearranging the equation to rpm = K*sqrt{torque}. In this case, the new stall would be rpm = 150*sqrt{500} = 3350. This formula isn't perfect. It won't work if the engines have wildly different torque curve, for example. And it won't tell if a particular converter will hold togther under markedly increased torque. But it gives a decent ballpark estimate and serves to illustrate a basic aspect of torque converter funtion.
One peripherally related question that may have occurred to you is "why are high stall converters more expensive". In general, it's because all else being equal, a higher stall converter will be physically smaller. Because it has to absorb the same energy with smaller components, the components must be stronger, which is to say more expensive!
The forces in a converter are quite high, and they generate a lot of heat. When a converter is stalled, all of the hp the motor produces is being turned into heat. Since a converter is always "slipping", even when cruising, a lot of heat is generated. And since high stall converters "slip" more under acceleration and at lower speeds, they generate a lot more heat than tighter converters. That's why you must have a trans cooler if you run a high stall converter, especially if you are racing and stalling the converter. Another way to keep heat under control is to use a larger capacity pan. The fabricated pans look cool, but are quite expensive. And compared to cast aluminum, they do not reinforce the transmission case, which can contribute to longevity under extreme use. So I recommend a deep, cast aluminum pan for performance users. Heat control is not only important for longevity. If you are a bracket racer, keeping tranny temps relatively constant will contribute to consistency.
Using this formula, I would add a couple hundred to the number that you come up with just to be on the safe side.
For example, if a motor has 400 ft-lbs. of torque and stalls a particular converter at 3,000rpm, K = 3,000/sqrt{400} = 150. Since we know K = 150, we can predict the new stall speed if torque is increased to say 500 ft-lbs by rearranging the equation to rpm = K*sqrt{torque}. In this case, the new stall would be rpm = 150*sqrt{500} = 3350. This formula isn't perfect. It won't work if the engines have wildly different torque curve, for example. And it won't tell if a particular converter will hold togther under markedly increased torque. But it gives a decent ballpark estimate and serves to illustrate a basic aspect of torque converter funtion.
One peripherally related question that may have occurred to you is "why are high stall converters more expensive". In general, it's because all else being equal, a higher stall converter will be physically smaller. Because it has to absorb the same energy with smaller components, the components must be stronger, which is to say more expensive!
The forces in a converter are quite high, and they generate a lot of heat. When a converter is stalled, all of the hp the motor produces is being turned into heat. Since a converter is always "slipping", even when cruising, a lot of heat is generated. And since high stall converters "slip" more under acceleration and at lower speeds, they generate a lot more heat than tighter converters. That's why you must have a trans cooler if you run a high stall converter, especially if you are racing and stalling the converter. Another way to keep heat under control is to use a larger capacity pan. The fabricated pans look cool, but are quite expensive. And compared to cast aluminum, they do not reinforce the transmission case, which can contribute to longevity under extreme use. So I recommend a deep, cast aluminum pan for performance users. Heat control is not only important for longevity. If you are a bracket racer, keeping tranny temps relatively constant will contribute to consistency.
Using this formula, I would add a couple hundred to the number that you come up with just to be on the safe side.
#10
10-17-2006, 11:50 PM
RE: Torque Converter
Good explanation man, but I would like to add that a lock-up torque converter will not slip at all when in lock-up mode...it's definatly somnthing to consider when talking about TQ converters.