How a torque converter works...By Z28Pete
#1
12-08-2006, 09:12 PM
How a torque converter works...By Z28Pete
The stall speed is the highest speed the input shaft can spin while the output shaft is locked. A 3000 speed stall, indicates that the engine at WOT can only get to 3000 RPM while the output shaft of the transmission is locked, such as when flooring the throttle while the brakes are locked. The problem is that the same torque converter will have different stall speeds depending on how strong the engine is. So a torque converter having a 3000 RPM stall on a 3.4 V6 will probably have 6000 RPM stall, or even explode when installed behind a blown 502" V8. This aside, the higher the stall speed the higher the torque multiplication, which also allows the car to take off while the engine is revving around the sweet spot. However, nothing comes free, because as the RPM increase the less efficient the torque converter becomes, so you have to find a happy medium.
A high stall speed allows a lot of slippage at part throttle which heats up the transmission fluid, so additional cooling is needed to keep things from getting deep fried. A Torque Converter Clutch, TTC, comes with most late model transmissions and locks up the torque converter to prevent slippage at road speeds. However, the TCC is not strong enough to hold the full power of the engine, and is set up to automatically relase before it gets overloaded, and also to prevent lugging the engine. This may or may not happen on a modified engine. If the TCC does not release on time it will burn out, and there goes the fuel mileage.
In general the higher the stall speed, the smaller the diameter of the torque converter, but not always true. The converters built for racing, use furnace brazed blades, stronger internal parts, and a stronger case to keep it from balloning out or even blowing up under heavy power loads.
Building these things is not a perfect science, but more of an art, so be very careful where you buy one from.
Additional info provided by JD1969:
Some companies to consider would be Yank and Fuddle. Both are offer good products but be ready to spend some coin. I cannot stress enough that you get what you pay for with a torque converter
_____________________________
Pete
Thanks for the great info Pete!!
A high stall speed allows a lot of slippage at part throttle which heats up the transmission fluid, so additional cooling is needed to keep things from getting deep fried. A Torque Converter Clutch, TTC, comes with most late model transmissions and locks up the torque converter to prevent slippage at road speeds. However, the TCC is not strong enough to hold the full power of the engine, and is set up to automatically relase before it gets overloaded, and also to prevent lugging the engine. This may or may not happen on a modified engine. If the TCC does not release on time it will burn out, and there goes the fuel mileage.
In general the higher the stall speed, the smaller the diameter of the torque converter, but not always true. The converters built for racing, use furnace brazed blades, stronger internal parts, and a stronger case to keep it from balloning out or even blowing up under heavy power loads.
Building these things is not a perfect science, but more of an art, so be very careful where you buy one from.
Additional info provided by JD1969:
Some companies to consider would be Yank and Fuddle. Both are offer good products but be ready to spend some coin. I cannot stress enough that you get what you pay for with a torque converter
_____________________________
Pete
Thanks for the great info Pete!!
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