He's doing it wrong!
The revs should get nowhere near the red line, and you should do it for nowhere near 30 seconds.
Think about what happens when you take off at full throttle in an automatic car. Engine revs rise immediately to perhaps around 2000-2500 RPM then, as the car gains speed, the revs increase until it eventually changes up at around the red line RPM.
Imagine that the car never accelerates but is anchored to the road. Engine revs will just sit at the initial 2000-2500 RPM.
The reason for this is that the torque converter has a "stall speed" which is the difference between the input and output speed for a given amount of torque applied from the engine. At maximum engine load and zero road speed, this is equal to the engine RPM, hence the method of measuring it.
The stall speed of the torque converter is selected to allow the engine to reach a speed where it's developing a reasonable amount of torque as the car pulls away, giving good acceleration from rest. It's analogous to the few seconds where you slip the clutch as you pull away in a manual car. If you don't do that, the car bogs down in the region between idle speed and about 2000 RPM where the engine is making very little torque.
With the torque converter stalled, the output torque of the engine is multiplied by a factor, actually giving more turning force into the gearbox than the engine is producing. This effect occurs when there is maximum load on the engine. As the engine load decreases and the vehicle gains speed, the torque converter unstalls, the torque multiplication reduces and it starts to behave more as a solid coupling like the clutch you have in a manual box. So, the torque converter behaves as a kind of continuously-variable gearbox. At a certain speed, most automatic transmissions pull in a clutch which disables the torque converter for added fuel economy (torque converter lockup). This happens at about 45 MPH in an Omega under light load, and considerably faster under full load.
If the stall speed is too low, the car is really sluggish off the line, as not enough torque is available from the engine until the vehicle has accelerated a little. If it's too high, fuel consumption is affected, as the torque converter operates inefficiently, unnecessarily multiplying the engine torque when it's not required.
The stall speed for a given application is fixed by the design of the torque converter. Testing it does give you some information about the condition of the engine and transmission, though. If the stall speed is not within the expected range, it can point to a few faults:
1) Engine performance is poor (low torque output gives low stall speed)
2) Brake bands / clutches in the gearbox are slipping
3) The torque converter is faulty (although there's not a great deal that can go wrong with them)
4) ATF is in poor condition or the level is low
5) Torque converter is not filling with ATF (filer blocked / pump problem)
The reason you only want to do it for a few seconds is that during that time, the torque converter is taking 100% of the engine output and turning it into heat, so you need to be careful that you don't overheat it.
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Topic: Automatic 'stall test'. Your thoughts (Read 3636 times)