Audi 2010 S4 Sport Differential Interview W Dr. Johan Fuchs

[bachiist]

Passive, mechanical system has natural response over broader driving environment that active system doesn't always have.

If two systems achieve the same performance, the simpler mechanical system is more desired (=One of the reasons Audi has kept the mechanical system).

I think B8S4 system (=Type C Torsen Ctr Diff w/ZF Active Torque Vectoring Rear diff) is a good architecture that is a good mix of both worlds.

- Another ACNA member

[Amidat]

@bachiist - yeah and Audi just switched it up again... they are no longer using Torsen going forward... they are using their own in house crown gear center diff...

[bachiist]

Thanks for uploading this.

AWD system cannot be judged by advertised merits alone.

Active System: Pro=Engineer can program system behavior Con=Programming will determine the system effectiveness, for better or worse There is inherent delay in system response

Passive System: Pro=Natural response, No delay (if Torsen) Con=Less tailoring of system behavior

[Amidat]

my question is why would they not put this on every model as standard in the U.S. Acura has their SH-AWD on the RL, TL, RDX, and MDX. Audi should be in the forefront.

[sspope]

Acura/Honda has crap AWD.

[gazboselectamo]

@sspope I think you'll find (if you bothered do to any research) SH-AWD is superior to Audi's quattro in pretty much every way. Do you even understand how "quattro" works?

[Amidat]

@gazboselectamo - not true...SH-AWD is only more electronic (not superior)...but that doesn't translate into real world performance...

[gazboselectamo]

@Amidat I'm not sure what you mean by "more electronic", both systems are electronically controlled and both use a gear and clutch system to distribute torque. As far as "real world peformance" the two systems will be very very similar, except the Honda system can overdrive the rear axle and transfer 100% of the rear torque left and right which should give it the edge. There's no way of comparing of course as there is simply no Honda that has enough raw grunt to make use of their awesome system!

[Amidat]

@gazboselectamo - you are correct if you are talking about the rear axle...but I the whole system. The Quattro is mechanical and has a torque "sway" of 40/60 to 15/85. Honda's system (Honda is my favorite of the mainstream car companies) is electronically controlled overall and goes 70/30 to 30/70. For a real world comparison check the test on Youtube of the Honda Legend vs. BMW 5 vs. Audi A6. The Acura RL (Honda Legend) is actually the most powerful of the 3 but came in last..

[gazboselectamo]

@Amidat I see what you're getting at, specifically the centre diff. But then why would Audi replace their "mechanical solution" on the new and top model RS5 with an electronically controlled diff if it did not perform as well?! As far as that comparison test, I've seen it and I think Mr. Plato completely missed the reason why the Legend was so slow, nothing to do with suspension stiffness! It weighs almost 400kg more than the BMW!! Not suprised it lost!

[Amidat]

@gazboselectamo - the RS5 is still a very much mechanical center differential. There is "electronic torque vectoring" which brakes the inside wheels in a turn....but the center diff is a crown gear.. no computer involved in that.

[gazboselectamo]

@Amidat I was under the impression the clutch packs on the centre diff were computer controlled as they are at the rear, maybe not!? Still not convinced that Quattro is superior simply because it's more simple. SH-AWD can send more torque left/right at the rear so the actual % torque that reaches the wheel that counts will be similar with both systems. I would like to see a manual Acura TL with SH-AWD up against an Audi S4 as that would be a reasonably fair comparison weight/power wise!

[Amidat]

@gazboselectamo - I don't think Quattro is better because it's "more simple"...computer programming doesn't make the Honda system better. Quattro is proven (and actually has gotten more simple over the years). The Honda system is good though...it's the same way ppl can't make steering as sweet as Porsche or BMW... It's just how things go.

[gazboselectamo]

@Amidat I think we'll just have to agree to disagree! I think the current generation of Quattro seems quite effective and it's good to see Audi pushing forwards - they obviously want their next gen RS cars to compete with and beat the new M cars. I just don't think Quattro is deserving of all the praise it's had over the years as there are several superior systems out there - Nissan and Mitsubishi have been leagues ahead for years.

[Amidat]

@gazboselectamo - From a performance standpoint Nissan and Mitsubishi have had "superior" systems. However, those are "specialty" systems. You are referring to the GTR and the Lancer Evolution. Infiniti's X can't match. Quattros actually used to be an almost "off-road" system....but they have lost some of that capability for on road performance. Also they trade some durability for all out performance (except the R8). It's all about balance when you are trying to sell cars to a wide audience

[gazboselectamo]

@Amidat I'm not exactly sure what you mean by speciality, Nissan's ATTESA systems have been used on dozens of their models - and is the same system used by Nissan's Infiniti brand. Mitsubishi likewise use different AWC systems across a whole range. The top level of Quattro until recently was no more advanced than the lowest level of ATTESA or AWC - it's taken almost 15yrs for Audi to even look into advanced torque vectoring.

[gazboselectamo]

@Amidat On a side note, the new R8 is rumoured to use active diffs front AND rear. I'm not sure there has been any car to do that yet - could well be Audi are attempting an overtaking manoeuvre and not content with just drawing parallel!

[Amidat]

@gazboselectamo - I have no idea about the new R8 but I'm sure it will share the system with Audi's subsidiary Lamborghini. Again "active" doesn't always mean better. If that was the case EVERY car would have "active" steering and "active" suspensions as well.

[gazboselectamo]

@Amidat They wouldn't because it's not within the budget of every car to have active suspension and transmission components.

[Amidat]

@gazboselectamo - of course it's not in the budget....but even exotics...how many of them use "active" steering or "active" suspension. Some....but only a few. It's just like craftsmanship....things may be automated and faster - but that doesn't mean you can build a structure better than the builders of old.

[Amidat]

@gazboselectamo - The GTR is an optimized chassis for Nissan's system. It's great performing ...but in foul weather it's actually not that good (at least with standard tires). Infiniti's are not balanced in the AWD set-up which is why they never offer them for comparison. Again - in foul weather (for cars) - only Subaru is up there with Quattro. That's what I mean by balance. You have on-road and foul weather performance. Then you have dry weather performance and safety. Seperate.

[gazboselectamo]

@Amidat I've never heard of anyone saying the ATESSA system does not work well in wet weather or snowy conditions - equally I've never read that the Quattro system is particularly outstanding in these conditions. Where is your source for this information? The reason Audi have had to step up there game is because all older generations of quattro with the simple torsen centre diff and open diffs front/rear have inherent understeer uncorrectable by any means other than replacing the rear diff.

[Amidat]

@gazboselectamo - manufacturers don't like to give magss their AWD sedans to test against Quattro's or Subaru's....the same with steering of a Porsche or BMW - no matter how "advanced" the steering and suspension system. You didn't know they were the best in bad weather?? The old quattro was essentially what a Hummer now uses...so yes it did understeer. They still want to stay mechanical because they don't want to betray their roots of "all weather" performance. EVERYTHING is a trade-off!

[Amidat]

@gazboselectamo - check the november 2010 issue of Automobile magazine.  They compare the AWD systems in the Acura ZDX - Subaru Outback - and Audi Q5. They praised the Acura system for switching torque side to side better than the other two....but other than that they didn't think it was so "special". It struggled in two tests (though one is partly because of ground clearance) and was noted as being slower to react than the Quattro.

[ZKev1]

@Amidat early gtr's are known to oversteer in the wet far too much, torque split controllers came out and sorted this problem out by fooling the centre accelerometer, in wet weather with a torque split controller the early gtr's are now awesome, the controller is a amazing mod for anyone with a attessa ets pro set up

[Amidat]

@ZKev1 - thanks for the insight... that proves my point... each system was designed with some target in mind and had to compromise other things to get there... then over time systems are re-designed to bring more balance to them. Audi for instance started their quattro success in rallying... so that obviously shows what there starting point was. They have had to refine it more for on-road performance... quattro being banned for road racing for so long probably made that shift take longer.

[conek2]

Audi has LSD, DSP, TR, QR, VW, GSP, ASP, MSP and LOL-WTF. Beat that Acura!

[gazboselectamo]

@conek2 I'm not sure what half those acronyms were but I think you'll find Audi's "quattro" is not as advanced as you think. The new "sport diff" is basically the same concept as Mitsubishi's AYC. Only 15 years late to the party then...

[gazboselectamo]

@Amidat Because Audi have to turn everything into an option so that their customers have more "choice" (so they can squeeze more money out of ya).