Quote:
Originally Posted by samchoi604
due to the space requirement nature of the torsen quattro, it would not work in the A3/S3 as it would require pushing the engine further to the front, causing the front to be heavier and forcing Audi add more heft (length) to the rear to balance it out, and you would end up with a car with the same size and weight as an A4/S4. I don't think it is a cost-saving decision, but application and form factor that dictated which AWD system is used.
With that said, Haldex is not bad at all and test have shown that Volvos with Haldex has the best grip in snow conditions. It was a test conducted by a german magazine and compared it against all the other types of AWD. If you google around you will find it. Also, Audi's second fastest car to the R8 is the TT RS, which obviously is using Haldex.
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The problem with Haldex has never been an inability to find grip, or even to deliver competent lap times (there's a lot more to it than AWD). The problem with Haldex has always been how it affects handling.
Until very recently, Haldex worked solely by detecting slip at the front wheels, which would trigger the engagement of a clutch that drives the real wheels. The mechanism that enacts this engagement has changed over time, but the fundamental issue has always been that the front tires must slip before the rear differential is engaged. The most recent revision to Haldex (offered in the TT RS) uses additional factors to determine when to engage the rear differential. The system is new though, so the jury is still out.
Once you have front wheel slip, you have understeer. There's simply no way around that, and so Haldex equipped cars are (er, were?) plagued with FWD-like understeer. It is possible to "power through" the understeer — when in doubt, throttle out — but it doesn't deliver a remarkably enjoyable driving experience for most people.
If your needs are practical, then Haldex is fine. It'll get your car going in the snow/mud way better than FWD. BMW has built its brand on something more than practicality though. "The Ultimate Driving Machine" shouldn't push through corners like a tractor.
Admittedly, that is a severe indictment of a car that hasn't even been released yet, and as everyone loves to point out, the Mini Cooper is a hilariously fun-to-drive FWD car. Still, it is a little discouraging to see the market developing like this. At the entry-point of the market, FWD or FWD-biased AWD systems appear to be your only options.