Is the torque split 50/50 F/R on the A4 1.8 TQS?

[B5QUAT]

Just wondering. Some 4wd systems, I believe, are either front or rear wheel biased and some are straight 50/50.

What is the split on the B5 A4, does anyone know?

Just out of interest as I just kicked the arse out on mine accelearting out of a junction. Behaved just like a RWD car normally does, only a bit more predictable and not quite as fierce. Just never had that happen before on a 4wd car. Used to driving understeery Imprezas. Got me wondering.

Cheers

[aragorn]

The centre diff is a Torsen, which is a peculiar device and acts in some odd ways.

What this means is that when you have full traction (or absolutely no traction) the diff acts as an open diff, and as a result sends power 50:50.

When slip occurs, a torsen cannot fully lock, what it does is acts like a torque multiplier. So for instance when you launch the car you might apply 100lbft to each axle. The car hunches down, weight comes off the front axle and the front wheels spin up. At this point, the front wheels are still transmitting SOME torque to the road surface, and the Torsen can then apply twice this amount of torque to the rear axle. So the front might have enough grip to apply 50lbft to the road, and the torsen will then apply 100lbft to the rear in response until the slip stops.

This is why with NO traction on one axle (say you've broken a shaft or become airbourne) the torsen will just act like an open diff, 2 x nothing is nothing.

What it does mean though is as you've found you can get the arse out quite nicely in some situations. Typically wet roads or touching one wheel onto the gravel at the side of the road for instance can be enough for the torsen to shove a good chunk of the power rearwards and the arse then steps out. It'll often do it in snow as well.

The newer torsens fitted to the B7 RS4 and other newer models have a greater bias ratio, they can put four times the front power rearward, and some companies offer modifications to some of the b5 diffs for a greater bias ratio.

[B5QUAT]

Brilliant response, thanks for that. That explains the behaviour perfectly.

These A4s are even more fun than I thought!

[Bradderz_1988]

Yep had this in mine especially more this time of year and especially because I have my Pirelli tyres on the rear and maxxis on the front it tends to spin the fronts a lot.