How does the AWD system on the 225Q deal with wheelspin on inside front wheel?
 

Or not.

I've posted a couple of times about the fact that my rear wheels don't seem to lock up with the fronts as they are supposed to, and I'm finally taking it into the dealership on Monday for them to take a look at it.

The problem is that's it's intermittant. Sometimes it all seems seamless, at others there's a slight clunk as it locks up, and at still others it doesn't seem to want to play at all and there's just tyre squeal.

Now, my last question for the Brain Trust here before I tackle the dealership - how does the AWD system on the 225Q deal with traction on a spinning inside front wheel? I seem to get some when pulling away (quite agressively) from rest while turning. Turning left from a stop light for example.

Am I just expecting too much?<p>Rob Ward
TT Roadster 225
Tustin, CA

It takes a weight transfer...
 

... for the inside front wheel to behave any differently in the fwd condition (zero slip). After that, the bias is to stabilize the front-drive balance and only transfer weight to the rear if there continues to be more power than can be transferred to the front wheels without slip.

You should always be doing ONE of the following things at any given time, no more.

1) accelerating
2) braking
3) turning
4) shifting

There are exceptions, you can downshift while turning and can accelerate while shifting, etc.

In general, if you're depending on the car's brains, you're expecting too much of ECU and not enough of grey matter.

The car WILL lock up the rear wheels in a hurry if put in an unstable condition, example:

While getting onto a wet onramp (I-94 at 3am at Town Line 60 for those in the Chicago area) in the 180Q, I shifted fourth to second under full throttle (MarkI suspension) and got the car to quite happily swing around. Once it started sliding and quattro realized there was WAY more power than available traction, the power went wherever grip could be found.

Sometimes there's only so much grip, and power needs to be shifted around pretty decisively. Sometimes it clunks, sometimes it doesn't, but you're pulling some wild stunts if you're getting it to clunk consistently.

Or... something's not workin' right.

Cameron

So, if I'm accelerating hard through 1st and 2nd as I turn (left) onto a street, for example,
 

I should accept some loss of grip from the inside front?

That's fine. I'm just not sure yet what to expect from AWD. I guess I had expected 100% grip at all times. Not very realistic of me.<p>Rob Ward
TT Roadster 225
Tustin, CA

ECU should apply brake to the spinning wheel

Why would the ECU apply the brakes?
 

This does not make any sense. The ECU should NEVER apply the brakes to any of the wheels, especially if they are spinning. :)

Don't confuse what Rob's problem is with ESP helping him out. ESP and the problem that Rob has with his car are two different animals.

Rob is experiencing a problem with his Haldex system it seems. He is able to spin all of his wheels or just continue to spin a front wheel without the Haldex system stopping it. That is a problem with the car, not with the design of the car.

That would be normal loss of grip . .
 

The inside front wheel will always lose some grip, it is how a car handles. The inertia of the movement of the car is putting the forces onto the OUTSIDE front wheel, that is why you feel the inside front slipping. At this point the car should be putting more power to the outside front wheel, once that wheel slips 15*, then the Haldex system will have the rear wheels come into the equation. Until the rears are hooked up with some power, then you are just a Fwd car.

This is how any Fwd car will take a turn. The power is transferred back and forth between the front wheels to whatever wheel has the traction. Why would you want to waste hp/torque on a non-traction wheel?

When I test drove a Fwd TT I had the ASR light coming on all of the time, especially on off-camber up hill turns. I was able to get those wheels to spin like crazy. Same thing with the TTQ, except the transfer of power is much better to each wheel. We have a transfer case that transfers the power to each wheel, the Fwd TT does not have this.

Don't forget that an inside wheel and an outside wheel are spinning at two different speeds and one of them will eventually slip. I am talking about a production car under extreme conditions, not normal every day driving! :)

Rob, it really sounds like you have a Haldex problem. believe me, not too many people are driving their TT's harder than I have driven mine. I can't get the tires to break loose the way you are describing. The times when I have gotten all 4 wheels to leave some rubber is when I did my 0-60 runs and was trying to maximum traction and variying my launches. It only lasted for fractions of seconds, but I did hear all four wheels spin and make lots of noise.

Let us know what the results are from the dealer. Good luck. Don't let them tell you this is normal . . .IT IS NOT! Prove it to them and yourself by test driving a 225TTQ they have on the lot! :)

As I said before, if you're spinning your inside wheel you have a Haldex problem. (more)
 

It's impossible (under normal driving) to spin any of the wheels. I've only spun wheels (momentarily) while driving on gravel roads.

Several posters have said that even dropping the clutch at 4000 to 5000rpm from rest only gives a momentary "chirp" of the tires.

So, off to the dealer to check it out.<p><img src="http://pictureposter.audiworld.com/AudiWorldPics/2000/keyfob.jpg">
"The key to having fun"

ChrisTTopher Lloyd

2001 225 TTQ coupe Silver/Ebony
Premium package, Audio package, Navigation System

Brake is applied to the spinning wheel so that torque can be applied to the non-spinning wheel
 

on the same axle. The differential needs the reaction force supplied by the brake.

Don't you mean ESP Traction Control?
 

<p>2001
225QR
No mods, yet!

Audi is using the acronym EDL
 

Anti-lock brake system (ABS) with Electronic Differential Lock (EDL) and electronic rear brake pressure regulation