At 12:41 AM 4/27/01 -0500, you wrote:
>Could someone please explain flash in relation to torque converters? Kirk
Stall is the rpm at which the converter will hold the ENGINE speed and
not allow further gains. The rpm at which stall occurs with a given
converter is a function of engine peak torque.
Stall speed can be measured in two ways, true stall and flash stall.
True stall is the maximum engine rpm that can be achieved with the transmission
in gear, with the brakes locked and the engine held at full throttle. True
stall is
difficult to measure without a transbrake installed in the transmission due
to the fact
that in almost every application the drive wheels will drive through the
brakes,
primarily because the brakes are trying to hold the drive wheels after the
rear end gear
ratio.
Flash stall is the maximum rpm that the engine achieves from a full
throttle launch
from a dead stop, not being held back by any kind of brakes. Because on a
launch,
the converter sees less load than it would see under a fully loaded stall
test, the flash
stall will almost always be lower than the true stall. Flash stall can
change just by
changing the load that the converter sees. For example, if your vehicle
has a 4.10
rear gear and the flash stall you achieve is 2800 rpm on a launch, you can
get a flash
stall of 3000 rpm by changing the rear gear to a 3.90.
The stock converter on our Dakotas have about a 2000-2200 flash stall
depending on
weight, gear ratio, peak torque rpm, shape of the torque curve of the
engine, etc.
Most makers of torque converters use flash stall figures in their
advertisement but
it is always to play it safe and ask them which stall they are talking about.
HTH. Bob
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