Interesting FACTS re Torsen and Haldex from a recent dyno day
08-02-2001, 04:50 PM
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Interesting FACTS re Torsen and Haldex from a recent dyno day
From recent threads on the Haldex v Torsen I would like to add some FACTS to rebutt some statements which were made.
STATEMENT 1 : Haldex has a greater power loss that Torsen.
FACT: Both are about the same. This Dyno (locally made in Australia, exported globally) can measure drive train loss - I wont go into how here. The Torsen equipped Audi's (URS4, 90q, 1.8Tq and RS4) and the Haldex equipped Audi's (S3 and TTq ) all showed between 16 and 17 % drive train loss.
STATEMENT 2: Haldex can only achieve up to 50% drive to the rear wheels.
FACT : These Dynos also measure torque split. The TTq and S3 showed a torque split of 49% front, 51% rear, plus/minus 2% throughout the dyno run.
This should clear a few things up, but alas I think that may not be the case.
Graham
STATEMENT 1 : Haldex has a greater power loss that Torsen.
FACT: Both are about the same. This Dyno (locally made in Australia, exported globally) can measure drive train loss - I wont go into how here. The Torsen equipped Audi's (URS4, 90q, 1.8Tq and RS4) and the Haldex equipped Audi's (S3 and TTq ) all showed between 16 and 17 % drive train loss.
STATEMENT 2: Haldex can only achieve up to 50% drive to the rear wheels.
FACT : These Dynos also measure torque split. The TTq and S3 showed a torque split of 49% front, 51% rear, plus/minus 2% throughout the dyno run.
This should clear a few things up, but alas I think that may not be the case.
Graham
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08-02-2001, 06:14 PM
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Seems to me a 4-wheel chassis dyno would necessarily require a 50-50 torque split.
It's not a roadway where the fronts could propel the car and the rears tag along for the ride; as the fronts drive the front dyno roll, there is a speed difference front-to-rear, and the Haldex or Torsen engages the rears to drive the rear dyno rolls. Unless the fronts are spinning (losing traction) on the dyno rolls, you get a 50-50 split.
Maybe I'm missing something. John S?
It would be interesting to know the details of how this particular dyno measures drivetrain losses. 16-17% sounds very reasonable.
FWIW: bevel gears can be used to change direction 90 degrees. They generate more sliding friction (and therefore losses) than gears with parallel axes (like in most transmissions). Worst case is hypoid bevel like you would find in a solid rear axle truck or car. Here the axes of the gears are not only at 90 degrees to change direction from the drive shaft to the drive axles, but the pinion (attached to the drive shaft) is lower than the axles for lower floorpan humps. This creates more sliding friction in the mesh of the gears, but they are very strong.
Maybe I'm missing something. John S?
It would be interesting to know the details of how this particular dyno measures drivetrain losses. 16-17% sounds very reasonable.
FWIW: bevel gears can be used to change direction 90 degrees. They generate more sliding friction (and therefore losses) than gears with parallel axes (like in most transmissions). Worst case is hypoid bevel like you would find in a solid rear axle truck or car. Here the axes of the gears are not only at 90 degrees to change direction from the drive shaft to the drive axles, but the pinion (attached to the drive shaft) is lower than the axles for lower floorpan humps. This creates more sliding friction in the mesh of the gears, but they are very strong.