| kanundrum |
11-26-2013 08:02 PM |
Quote:
Originally Posted by OrbitalEllipses
(Post 1355127)
That doesn't make sense.
Non-biased AWD is permanent 50/50 torque split front/rear. A lot of permanent AWD cars have bias to the rear, slightly (STI had up to 70% I think in some years). My question is: does Haldex drive all the wheels all the time, or does it send power to the rear when it detects slip? That's difference between the Haldex and quattro systems Audi uses: Haldex is poop, quattro is not.
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Dang they are on Gen 5 now. I had the better performing Gen4 Unit.
Haldex Generation III, IV, and V based all wheel drive systems are proactive. The electronics can pre-tension the clutch and activate all wheel drive before a wheel slip occurs This is what I meant by the system is always monitoring every millisecond and sending power where its needed but you are right they are defaults.
Gen V Haldex, smaller unit, instant traction, torque to all four wheels with the 50/50 split and the FWD bias split goes up to 95/5.
and Gen 4
The XWD system can transmit 100 percent of available torque to either the front or rear wheels. However, for those conditions to occur one end of the vehicle would have to lose all traction, like driving on ice for instance. During a standing start the rear wheels are put to use, without the need for any slip to occur. Then under straight-line cruising conditions, to conserve fuel and driveline wear, the torque split to the rear wheels is reduced to a level between 5 and 10 percent. Also up to 40 percent of torque can be transferred by the eLSD between the two rear wheels to the one with more grip. The system can adjust torque splits based on calculated conditions, such as those that indicate an aggressive lane change maneuver, to effectively reduce overstreer or understeer without any wheel slip occurring. In the event that some wheel slip does actually get to occur, the system can react more timely and efficiently than in the past.
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