Lasse Norway

Some people say that the Quattro used in thr TT is not as good as the original Quattro which is used in A4, A6... They say the reason is that the TT is not a "real" permanent 4wd. I do not understand this.. I thought that the adjustible hydraulic system was quite a good idea! Anyone with some good arguments?<p>Lasse Norway

IslOMan

Seems so but each system is from completely different approaches to AWD. See the article below. In a transverse engine arrangement found in the TT, the Haldex parttime quattro system is used. In a longitudinal engine setup found in the A4, the Torsen fulltime quattro system is used.<ul><li><a href="http://www.findarticles.com/m3012/6_180/63565214/p1/article.jhtml">What's the Diff</a></li></ul>

Geza

is an on-demand AWD system which only applies engine torque to the rear axle when sufficient front wheel slip is detected. In "normal" mode, the TTQ is a front wheel drive car. The front axle has a locking differential, but there is no locking feature on the rear differential.

The quattro system used in most other Audis is a perminent full time system with a normal 50-50 front-rear torque split able to transfer up to about 70% (I've seen varing numbers in different Audi publications) automatically to the axle which has the most grip. Also, both the front and rear differentials are lockable through EDL (electronic differential lock).

I hessitate to say which is "better"; I will say that I prefer the "conventional" quattro system; to me it seems more seemless, as it is always there and doesn't have to "turn on". Plus, although both systems add weight, at least the extra weight in the conventional system is being put to work all the time. Whereas, the Haldex system is rarely activated in normal driving (or even on in a race track environment).

strawtarget

While my gut reaction is that the Torsen is better than the Haldex, it may not really be the case. I think it's too easy to compare Haldex to a V.C. style AWD system because of the rear-wheels-only-on-demand nature of the beast. However, in a V.C. system, the rears don't connect to the fronts instantly like they do with Haldex. And the control is hardly precise in a V.C. system. Haldex is very precise, and is VERY quick to engage.

So if you think about it from this standpoint:
Q: When do I need AWD?
A: When you're turning, or accelerating, or in slippery conditions.

In that case, Haldex seems perfectly fine. When you're turning, the front wheels are moving faster than the rears so Haldex engages with the correct amount of torque. When you're accelerating quick enough, the front wheels might spin just a tiny tiny bit (1/4 of a rotation or less) and the Haldex will engage. When you're in the wet or snow, the Haldex will engage as soon as the front wheels slip.

So the Haldex is superior to a V.C. system that many other cars use. It's there when you need it.

Why do I still think the Torsen is a tiny bit better? It PREVENTS wheelslip by having a more even static torque split. Haldex reacts to slip instead of preventing it. Well, Haldex prevents it while you're turning since it will engage without actual wheelspin needing to occurr.

My 2 cents.

LeTThal

I've learned to anticipate it even tho it was a bit eerie at first, that slip-then-grip feeling when tearing round a corner. I know haldex will slip and grip, it's knowing when it grips and by how much that needs experience, as it varies with the tyres, the road surface and the weather conditions.

I sometimes would've preferred constant 4WD I think. But Haldex is supposed to be lighter and more "intelligent" and supposedly the 4WD system of choice in the future for most cars. I guess only time will tell. More "intelligent" isn't always better.

For those who don't drive adventurously, perhaps the question should be whether the front tyres will wear out faster in the Haldex system than the Quattro system? This is often the case with some FWD cars where the front tyres have to do all the driving and steering.

CarTTman

My wife drives an A4 2.8QT Avant & I have a 225C.

I find that the Torsen is probably better for all around and inclement weather driving because the power is always to all 4 wheels.

For performance driving, however, I continue to be amazed every time I push the TT through corners. The torque transfer is nearly instantaneous with Haldex, putting power to the wheels with the grip depending upon where you are in a turn. I honestly don't think that Torsen could allow you to on throttle as much through a turn as the Haldex, and Torsen definately won't pull you out of a turn like Haldex since the torque transfer isn't as fast or complete. So, with Haldex, you should definately be able to corner faster with a higher exit speed.

With that said, my TT will hibernate during the winter and the occasions in which it gets driven in the rain are rare, but my guess is that Haldex would be 'jerkier' in true foul weather conditions.<p><img src="http://utenti.tripod.it/~the_simpsons_family/bart/bart5.gif" border="0">

BillK

While the TT only has a diff lock up front. What that means is that the A4 can get moving if only <b>one</b> wheel has traction. If the TT is in the same situation, if one FRONT wheel has traction, you're fine, but if only one REAR wheel has traction you will spin your wheels fruitlessly...