esses

I was pulling out of a driveway today at a little more aggressively angled than normal. I managed to lift a wheel. When I accelerated away, the ESP light kicked in... wtf?! Wheel spin... umm isn't that where Quattro is supposed to kick in and use one of the other 3 (all of the other 3) wheels ?

Or is that EDL kicking in and using the ESP light to tell me?

TOPGUN750

Quattro acts like traction control on most cars.

ESP acts like the stability programs on most cars like BMWs.

I believe that quattro manages which wheel to give traction to while ESP manages stablity and the ability keep the car going in a straight line. ESP manages that through the restriction on engine power and braking.

CactuSavant

A quick search on Yahoo for

how does audi esp work

unearthed the following article:

<a href="http://www.vwvortex.com/news/02_00/02_11_00/index.shtml">http://www.vwvortex.com/news/02_00/02_11_00/index.shtml</a>

A great explanation of how ESP works.

Quattro in a nutshell (hope someone will correct me if I get something wrong):

At all times, the quattro in your S4 is directing torque to wheels. There are three differentials in the car; they determine how much torque gets sent to each wheel. The Torsen diff in the middle generally splits torque equally front and back. The Torsen diff works in such a way that if one end starts offering less resistance to turning, it will get less torque. So if, for instance, you're understeering heavily, it means the front wheels have broken loose; they will turn more easily; Torsen will send more torque to the back; and the car will straighten itself out. The other two diffs, front and back, are traditional diffs; they send torque to whichever wheel spins *more* easily. (Interestingly, this is exactly the opposite of what the Torsen diff does.) You need this for going around corners without destroying your tires, because the outside tires will have to travel a greater distance.

Hope this helps.

Tostao

coming from the ABS sensors sensing a wheel (or wheels) is acting 'strange' and needs to be 'checked' so, it can trigger the ABS pump on the wheel to slow it down so it regains traction.

It knows that, given the turning ratio (YAW sensors), the wheels should carry X speed and when you are sliding or loose control, the ESP brain will 'try' to help you by triggering ABS on certain wheels with certain sequence, etc.

adp

riding down a hill on a 10 speed bike, you can pedal all you want but unless you pedal faster that the wheels/gears are turning you will not add any drive.

Think of the 4 wheels of the car in the same light.. the engine is pedalling at a constant speed, and wheels that lose traction will not turn any faster than the wheel(s) with traction.

This is oversimplified - but a good starting point. Allowances for differentials needed for turning, etc, etc, etc all must be applied. This shoudl, however, give you an idea of how Quattro works as a traction control system all on it's own.

esses

when a wheel was off the ground? I would have imagined that was Quattro's job to keep the car going.

RogDog

Once triggered, ESP intrudes on, or overrides whatever quattro happens to be doing. I find it very difficult to take a corner aggressively with ESP on, that's why I usually have it off when I'm driving for fun.

Of course, I'm no expert. This is just a guess.

CactuSavant

I leave ESP on for day-to-day driving, esp in bad weather; but if I'm gonna do any eXtReMe driving, I turn it off.