NorthwestB9

My whole point is one I'll reiterate again. I'm not defending or knocking Torsen or Ultra. I'm defending the Audi brand by basically saying, try the thing before you dismiss it, as several of you have done here. I just shake my head when I see someone write in the comments section of every article I see on Ultra some variant of: "Well, I've bought my last Audi. The only way we can get them to stop this is to not buy one and hit their bottom line." And not one of them has ever driven one. That's the same impression I'm getting from critics here. Just because they read something from a spec, Ultra is automatically dismissed without ever having tried it. Personally, I think I'd be fine with either. I'm happy with the Torsen system I have now, but I'd probably equally be happy with Ultra. But I won't know until I try it. I'm not going to dismiss the whole thing as crap without having driven it around quite a bit.

rsilvers129

I need help fact-checking that. It sounds to me like the Audiwiki was saying that it does a solid lock after the torque difference (Torque Bias Ratio) reaches a preset amount of 70/30 or 15/85. At that difference, a lock is triggered. It could be that Ars Technica article is misunderstanding.

rsilvers129

I get the concept of if you can't tell the difference, it doesn't matter. But try telling that to people who pay twice as much for Organic milk. There is no difference in the milk, but they like what it says about them as a person.

People dismissing Ultra are probably into RWD cars, or RWD bias, and Ultra doesn't have that. RWD bias, even if you cannot feel it, says something about the buyer. And if you can't feel it, it would be due to the ESP tuning out some of the fun.

To the enthusiast Audi has pushed their torque split for a long time. Now they are trying to keep that market in some models, but also convert a base of buyers, mostly in Europe, who were turned off from AWD due to lower economy, to accept a new form of AWD that promises FWD-like economy. This new quattro is not going to be used on performance models. I have come to decide that the A4 6MT wasn't created for enthusiasts, but for economy drivers in Europe. I drove one, and the gearing seemed rather tall. It was all about economy and not driving feel.

Glisse

You are right, except it isn't mostly in Europe, it is mostly in the rest of the world. The UN WLTP/C (Worldwide harmonized Light vehicle Test Procedure) drive cycle commenced last month, and has a two year phase in period. In Europe, the RDE (Real Driving Emissions) test programme has been added as well. WLTP is a much more rigorous static (rolling road) drive cycle test than the NEDC/EPA test cycles. The RDE straps a mobile exhaust gas analyser to the car, which is then driven on roads. No place to hide, no easy way to manipulate results. These changes have a massive impact on measured efficiencies and emissions, and something all global car manufactures are trying to address.

It is for these reasons that, as someone noted earlier in this thread, Audi Germany have just moved the A4 and A5 2.0TFSI quattro from the self-locking centre diff system to quattro Ultra. But have left the high output 2.0TDI and low output 3.0TDI (both produce 400Nm torque) on the centre diff system. Reasons that the gasoline engine has moved, but not the diesels due to one of the following:

1. The diesels will remain in their current efficiency/emission bands without needing to use quattro Ultra (see point 3)
2. The 2 diesel engines produce around 8% more torque than the 2.0TFSI version discussed here, and are right on the 400Nm torque limit of quattro Ultra.
3. The quattro Ultra system costs more than the centre-diff system (despite your allegation that it is a cheaper system, which is not based on any facts I have come across)
4. Audi have production limitations on the quattro Ultra system.

The EPA was originally a participant in these proposed changes, but has pulled out. I can understand why those in the US might be either confused or annoyed by all these changes. However, I'm not sure the enthusiasts that post in the forum are representative of the broader population, who probably do want higher efficiency, etc, and wouldn't notice any dynamic penalty - which would be a theoretical penalty for many, I suspect. I think Audi have been going too far in trading off engine/drivetrain dynamics for efficiency myself - but this is a generalisation. Need to look at model by model, spec by spec. Same applies to most manufacturers.

Whether Audi also change the North American 2.0TFSI cars over is yet to be seen. But it should be noted that the DL382 S tronic transmission that is being used in the B9 "mid torque" models was designed to be used with FWD and quattro Ultra systems. It has a 400Nm torque limit. The DL501 S tronic was designed to be used with higher torque engines, and with the self-locking centre differential system and a rear torque bias. This has been covered before in these forums, in some detail. Audi adapted the DL382 to accept a self-locking centre differential at the end of its drive shaft, but this was not part of the original design. It works well enough, I have driven that combination plenty of times. I suspect it works even better with quattro Ultra, but have no empirical experience.

Yes, manual transmission cars in Europe are very popular. Because they cost less. Automated transmissions are aspirational. Funny old world.

And given your penchant for pedantry per your signature, Toyota own the Torsen trademark and patents, build Torsen branded products, and have for many years. Audi used Torsen differentials in the early days. They have used their own designs for many years but may pay some patent components. It is, at best, a Torsen style system. All this is on the Audi Technology site, which contains much information on all the various quattro systems. Not least exactly when quattro Ultra is proactive, predictive or reactive. An under-used resource by many here, as it is invariably more accurate than the second hand, anecdotal information contained in some of the media sites being quoted.

Finally, whilst I prefer high performance Audis myself, I have never read a complaint in any forum from any owner about their quattro Ultra system. The only complaints are coming from those who don't have it.

rsilvers129

Thank you for the detailed post. It has lots of useful information.

Also true that the only people who complain that a VW GTI is FWD are people who don't have them. I am not sure how much of that is because FWD is good vs people who dislike FWD don't buy GTIs to begin with.

Audi spends so much time talking about how they predict when to be in AWD, that they do not adequately address my real concern - handling dynamics. Yes, I believe that the car knows when to behave like a Haldex system when all wheels are active, but how good a job does it do with understeer, and is any degree of throttle steering possible? Even a little? Perhaps in Dynamic mode? I don't know the answer to this, but can inner-rear-wheel braking fully dial out understeer?

There would be no controversy if they added a clutch to the Torsen-style self-locking torque-biased differential, but that would have cost more.

Also, was I correct that this is false when Ars Technica says, "By default, the engine's torque is slightly rear-biased (40:60), but the mechanical center differential can let up to 70 percent of that go to the front wheels or 80 percent to the rear." I believe Ars Technica was confusing the fact that the Torsen-style differential fully locks when there is a torque difference exceeding a certain amount with it being able to shift 70 percent of torque to the front. It can't do that.

msochemist

Let see after 5-6 years which one will break first torsen or quattro ultra.

On top of that why decouple the clutch into fwd why not rwd?

audi8k

I think the TORSEN differential works the other way around. It use a sort of torgue multiplication between the axles up to the torque bias factor and then let go. So at a certain torque split ratio is can't hold back the slip of the axle with the less grip. This is what is mentioned as the maximum split like 15/85 or similar and not the nominal 40/60 split when the torque split is within the torque bias range.

rsilvers129

Wouldn't you need rear engine or two driveshafts to do that?

rsilvers129

This has some info: https://en.wikipedia.org/wiki/Torsen

superswiss

It's less complex. To make the rear axle the primary axle, Audi would have to move the transmission to the back and then have another drive shaft to the front, or use a more complex transfer case like BMW's X-drive. Audi uses FWD layouts for most of their cars, so making the front axle the primary axle is the easiest and least complex way. The only exception is the R8, where due to the mid engine design making the rear axle the primary axle is a no-brainer. Cars like the GT-R for example have very complicated drivetrains to have a rear biased electronic AWD system with the engine in the front. The GT-R for example has the transmission in the back to make it possible.

The AMG E36 and the upcoming M5 both use a multi-plate clutch AWD system, that can fully decouple the front axle. They both have a drift/2WD mode, which completely disconnects the front axle and makes the car a 100% RWD. I'm hoping we see these systems appear in the smaller M and AMG models and maybe Audi considers it for future RS models. The E36 and the M5 are just too big for my taste. I don't need all that space at a weight penalty of around 300 lbs.

Adding a clutch to the center differential setup would also be more complicated as the center diff would have to be able to be locked out, when the front axle is disconnect in order to properly send all the torque to the rear. More complicated usually means more weight.