TC Stall Test
- Thread starter JohnnyC
- Start date
Erik VanRenselaar
Member
First off: were you just curious, or do you think your trans/converter has problems? How were you performing your test?
Regarding torque converter stall speeds, there seems to be many misconceptions. A 2,000 rpm stall speed means that the torque converter reaches maximum friction potential at 2,000rpm.... Which would mean that you are then getting almost no torque multiplication from the torque converter. It is more of a 1:1 at the stall rpm.
Actually, at the rpm when the turbine is standing still (or stalled) and the pump (impeller) has reached its highest velocity, is when there is the maximum torque multiplication from the converter. The stator is not turning at that point, either, as it is being forced *backwards* by the fluid flow and is prevented from turning that way by the overrunning clutch inside the converter.
After this point, as engine rpm increases, the turbine turns faster. Torque multiplication tapers off during this. When the turbine speed is about 90% of pump speed, that is the *coupling point* of the torque converter (approx 1:1 ratio). That is when the converter is functioning like a fluid coupling, and there is no torque multiplication. The stator overrunning clutch has also *unlocked* at this time, and the stator is freewheeling with the turbine.
The blade angle/direction relationships (causing vortex flow) between the turbine, the stator, and the pump (or impeller) and the function of the internal overrunning clutch are what make the torque converter more than just a fluid coupling.
So, the torque converter's stall speed is the rpm at which the maximum torque multiplication is being created by the converter. The actual crankshaft torque input affects the converter's stall speed rpm (more engine torque moves the stall speed up in rpms).
Regarding torque converter stall speeds, there seems to be many misconceptions. A 2,000 rpm stall speed means that the torque converter reaches maximum friction potential at 2,000rpm.... Which would mean that you are then getting almost no torque multiplication from the torque converter. It is more of a 1:1 at the stall rpm.
Actually, at the rpm when the turbine is standing still (or stalled) and the pump (impeller) has reached its highest velocity, is when there is the maximum torque multiplication from the converter. The stator is not turning at that point, either, as it is being forced *backwards* by the fluid flow and is prevented from turning that way by the overrunning clutch inside the converter.
After this point, as engine rpm increases, the turbine turns faster. Torque multiplication tapers off during this. When the turbine speed is about 90% of pump speed, that is the *coupling point* of the torque converter (approx 1:1 ratio). That is when the converter is functioning like a fluid coupling, and there is no torque multiplication. The stator overrunning clutch has also *unlocked* at this time, and the stator is freewheeling with the turbine.
The blade angle/direction relationships (causing vortex flow) between the turbine, the stator, and the pump (or impeller) and the function of the internal overrunning clutch are what make the torque converter more than just a fluid coupling.
So, the torque converter's stall speed is the rpm at which the maximum torque multiplication is being created by the converter. The actual crankshaft torque input affects the converter's stall speed rpm (more engine torque moves the stall speed up in rpms).