‪Quattro vs xDrive - Audi Q5 gegen BMW X3‬‏ - YouTube

 

'Cause its a woman driver? That and the bmw probably had the properly rated tires for something like that

 

I guess X-drive is the bomb. I don't know? I had to look up to remember if a Q5 was Torsen or Haledex. It's a Torsen which it a good active front/rear split.

Only thing I can think of it a funny left / right split setup in the BMW favor for testing with the rollers. Common thought by a lot of people is AWD is all wheels all the time. Left and right has its own split but we all know that.

 

Much better torque control in the center diff.

 

Considering the apparatus has a large BMW X Drive logo on it, it may have been specifically designed for the BMW.

 

from reading AWD forums, the quattro is the most reputable and respected system. people say that quattro is more dynamic than the other systems. the electronically controlled AWD systems aren't as "fluid". but this test shows how horrible the center diff is from a stop.

 

This is actually what the deal with the video is. There is a similar one out there with an A8 and a BMW. The X-Drive is a Haldex system. There is a difference between Gen 2 and 4 of the Haldex, 2 is reactive 4 is proactive, but basicly if the wheel sensors detect slip, the front wheels are engaged. A Haldex is nothing more than a hydrolic clutch. If slip is detected the clutch is engaged and the front wheels get power, there is no center differential, hence why a Hadex system has to disconnect the front drive axle when not needed. VW products and the A3 use the Haldex, but for engaging the rear wheels.

A Torsen center diff is engaged at all times. (why the car has to get flatbeded if something happens). It does not engage as needed. Also it is a torque transfering device, not a true limited slip center diff. It takes the amount of torque getting to the pavement from the wheels with less grip and sends 2 to 4 times (depending on model) that amount to the axle with the most grip. The above senario occures when the axle with the least grip is transmitting 0 torque to the ground, such as with those rollers, ice, or with one wheel in the air. The other axle won't get any power, because you can't multiply 2 to 4 times the torque of "0". 0 x 2 or 0 x 4 is still zero torque that can be transfered. Audi's way around this is to have the brakes activate on the wheels with no grip and zero torque. The drag of the brakes causes the need for torque to spin them. The torque caused by the drag of the brakes is then sent by the torsen to the other axle. The Hummer has a Torsen on each axle and has the same problem if a wheel goes into the air, it will stop cold. To get moving again the driver applies the brakes enough to cause drag on the airborn wheel, enabling torque to get sent to the rest of the vehicle.

I almost wander if BMX disconnected the Traction control, ABS system on the Audi, so that the brakes couldn't engage to force torque to the other axle.

As of 2009 or 2010 Audi started putting some type of preload into the torsen system to prevent the above senario. Don't know if it still uses the brakes.

Sorry for the long explanation, but there is no other easy way to explain it.

 

Perfect explaination!

 

so was the test rigged? was the ESP turned off? i guess we'll never know.

 

I've had the above experience on ice. I'd hit the gas, and you could feel the wheels slip as the traction control light started blinking, causing the brakes to operate forcing the Torsen to transfer torque.

The Haldex, has improved quite alot since it was introduced. The first three generations only engaged the other axle if there was slippage. Axle speed differences pushed oil around and forced it against the clutch engaging it. The Generation 4 still does that, but adds an extra pump that operates independent of axle slipping. When it was first introduced in the Saab 9-3, it enabled the car to engage the rear axle if the stability control detected a sudden change in direction, or if the gas was suddenly punched. This way all wheels were engaged before slipping could occure. It also engaged all wheels when accelerating from a stop, then disconnected when the car achieved cruising speed.

I still prefer the Torsen setup though.