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Does anyone have any information on exactly how the Q4 system works (apart from the obvious 'it's a 4 wheel drive system...')?

I have previously owned a mark 1 Audi TT quattro but with this system, the front wheels only were driven until slip was detected and then the Haldex coupling would send some drive (up to about 30% I think) to the rear.

I understand that the Q4 system uses a Torsen centre diff but is this a permanent 4 wheel drive system or part time like the Audi? If it is permanent, does anybody now the % split front to rear?

Thanks,

Stuart.
 

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it's a permanent four wheel drive with a 43/57 split, which is almost the same as what the new Audis have.
 

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Yep, it's basicly the same Torsen C based system that is fitted to almost all new audi models.The difference consists, as toshy pointed out, in the ratio between front and there, 43/57.In my opinion this is a better setup that allows you a little more to play with the car.Even on wet roads when pushing the pedal hard you will experience some of what rwd owners do:the back kicking out. :)
 

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Torsen C centre differential is set up to send more torque to the back wheels. But it can send more torque to front wheels, if there is less grip on the rears.

It works almost exactly the same as the latest generation of Audi Quattro (not the Haldex fake quattro):
Torsen T-3 centre differential, 40:60 'default' split front-rear, automatically apportioning up to 80% of torque transfer to the front axle or up to 100% torque to the rear axle.
 

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Subaru WRX STI with DCCD (Drivers Center Controlled Differential) can do anything from 50/50 to 35/65 (front/rear)

For hard acceleration you want a bit more torque at the back...
 
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