The true meaning of spliting torque


H. Whelply

I've read all I can find on the different approaches to allocating power to
the Forester's wheels depending on MT or AT. But I've not read an
explanation of a simple question: what exactly does it mean that, say, 60%
of torque is going to the front wheels and 40% to the rear? Further, how is
that metered? (Yes, of course, the computer does it, but what's the
instrumentation?) And if somehow I could measure the torque in a situation
where my XT is running at exactly 3,600 RPM, and there was a 60/40 split in
effect, exactly 60% x 235 ft lbs (max rating on the XT turbo engine) or 141
ft lbs would be going to the front wheels and, therefore, 94 ft lbs would
be going to the rears? Given the limited-slip dif in the rear, could, say,
20% of that (18.8 ft lbs) go to one wheel and 75.2 ft lbs to the other? Is
the need for torque presumably gauged by the number of wheel revolutions in
a given time period relative to the other wheels, the other wheel on the
same "axel" considered first, then those at the other end of the car? OK,
enough questions.



Edward Hayes

The 60/40 Forester AT torque split is the default set by the transfer gear
set in the rear end of the transmission but in front of the continuously
variable clutch pack. The torque split ratio is determined by the TORQUE
DIFFERENCE detected between the front & rear. The manual default is 50/50
and will only change when a difference in WHEEL SPEED is detected. I would
guess that an AT vehicle running 60 mph would be torqueing the front or
rears differently so the default of 60/40 would be different and probability
favoring the rear at maybe 50/50?? hope this helps. eddie

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