Forum » General Tuning Discussion » Dynoing Variable Torque Split AWD; Transfer case/clutch pack wear...

Dynoing Variable Torque Split AWD; Transfer case/clutch pack wear...

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I have a question regarding dynoing an AWD car with variable torque split such as the R35 GTR.

Some claim that without the ability to drive the front axles to match rear axle speeds you wear out the clutch packs in the transfer case. The reason being that the car is forced to continually manage torque transfer to the front wheels to maintain a matched wheel speed.

Others, like this poster here, claim all that is necessary is the ability to apply load to maintain the same axle speed front-to-back. Essentially, allowing the driveline of the car to drive the front axles as needed while using the dyno's control loop to keep the front axle from overspeeding compared to the rear axle.

With a dyno roller/hub with low enough intertia I can see the second point being valid as it can't be very hard on the clutch packs to spin up those front wheels, but then it sounds like the GTR likes to throw transfer case temp warnings when on the dyno...

So, who can shed some light on this for me? Hopefully Andre and some others have some direct experience with this!

My personal experience with the R35 platform is very limited, however my old shop tuned a number of them on our Dynapack 4WD hub dyno with no trouble. I haven't seen it pan out as a real concern.

Thanks Andre,

So I'm clear, the Dynapacks aren't capable of motoring the front wheels, are they? They simply apply load, correct?

What kind of power/torque levels was your old shop seeing with those R35's?

Were they doing extensive steady-state or largely sweeps?

Correct. The dynapack can only apply load.

We never did any seriously modified R35's so maybe not the best example. We might have seen around 400-450 kW atw or thereabouts?