TTAC Commentator Jems86 writes:
A question for the B&B: Is the test above rigged?
Sajeev Answers:
Any test from a manufacturer is designed to excite and exploit, much like Senator McCarthy’s famous inquisitions. The mission: find a single flaw and promote the hell outta it. Then again, isn’t that what makes the blathering idiots who rant on 24 Hour News Channels so entertaining/revolting? But I digress.
Both BMW and Audi start out with a 40%-60% power distribution between front/rear axles. But while Audi uses a conventional locking center differential, the Bimmer has a transfer case that automatically varies front to rear power distribution via clutches and gearbox fluid. Cliff’s notes: one is a true differential, another is a clutch pack in a gearbox.
Let’s go downstream: BMW’s system uses open differentials at both axles, choosing instead to let the traction control nanny (i.e. the brakes) slow down one wheel to transfer power to the other. Audi’s Quattro uses a limited slip differential at both axles, to help the traction control work more effectively. And, in general, a “locker” is a better alternative, which is irrelevant here.
My guess is that BMW found a loophole in Audi’s proven “center diff and locker” engineering: BMW can transmit 100% power to either axle, this 100:0 or 0:100 ratio cannot happen in the Audi. I cannot find proof (via Google) to prove otherwise. Now I’m kicking myself for not making stronger ties with the world of Automotive PR: this query would ruffle feathers at Audi Flack Central.
If I’m wrong about the 100:0/0:100 ratio, there’s no reason for Audi to perform so poorly, unless sabotage (tires, software hacks, etc.) is involved. Rest assured, on the streets where normal people drive, the differences will be close to irrelevant.
Bonus! A Piston Slap Nugget of Wisdom:
This test is truly loony. I’m fine with the layout of the incline, but don’t ever drive like that in real life. If a vehicle loses traction on an incline and starts to roll down, go ahead and let it find a better hunk of terrain below the hill. Then start over and let momentum help you up the hill. Since both vehicles are diesels, there’s plenty of grunt afoot, so let the electro-mechanical bits do the right thing while not fighting the benefits of momentum.
Send your queries to mehta@ttac.com. Spare no details and ask for a speedy resolution if you’re in a hurry.
LSD does very little to improve 4×4 performance as shown in this video by Eaton (similar test with incline although they test left to right power transfer and not front to rear) Youtube
As for momentum argument, what if your rear tires were stuck in a snow drift? Then it appears the BMW is the vehicle of choice to get out of the situation.
Can’t argue with that. Which is pretty embarrassing for Quattro.
I still believe its rigged (other than the relatively unrealistic situation). A Torsen differential (which is what most “higher” Quattros are, is “TORque SENsing”. Meaning that in a situation where there is no torque on one set of wheels, it can not deliver any to the others. Which is what this test simulates.
However – afaik in the case of spinning wheels, Audi uses its ESC to deliberately brake that spinning wheel a little, which provides torque at the front wheels and therefore, at the back wheels. This for some reason does not happen in this video – my guess would be because the fuse has been taken out. Just a guess however.
A bit more realistic: Driving up a ski-course, done by a german TV-show. http://www.youtube.com/watch?v=EyKstZ6a5ag
Hi Guys,
the rear wheels on the Q5 are rolling freeway style…. if the system thinks they are not slipping, which they are not, why would it send all the power to the front? I don’t think there is a sabotage, it;s just that the rig is set up in a way to nulify the effect of the Quattro system.
Quattro doesn’t send much power to the front to begin with, and on a highway cruise, the bias to the front is not much if i’m not wrong. however if the system does actually sense slipping, the type you get where there is a loss of grip, it will boost the power to the frot and possibly get out of the jam.
whereas on the BMW the front wheels are always turning at a rate that can pull the car, ever at a highway cruise. it might be helpful in this seemingly impossible situation, but the quattro might prove to be more efficient as you cruise.
Another thing. if The Quattro want to pull out of this situation, it need to have more initial bias on the front axle, which it doesn’t have… cause it’s a RWD biased system that only works the front axle marginally to correct not to take over traction all-together in less than extreme situation. in this situation it’s overwhelmed…because it’s put to the test in a circumstance that is beyond its capability.
There is not specific sabotage, it’s the test itself that is skewed..
Like these things ever go off-road………
A snowy driveway on a hill is as close as these things get to using their incredible off-road power.
+1
You can pretty much guarantee that 99.9% of these vehicles would never see a gravel track, let alone any serious offroading.
Of course they won’t, and this isn’t an offroad test. That’s about underbody protection, articulation, angles and clearance. None of which this class of cars makes the slightest pretention at.
Climbing an icy driveway at some point is a reasonable expectation in most of the country. A drivetrain that can manage that gracefully in all seasons is a selling point.
Clearly, you’ve never been up my driveway after an ice storm.
The Audi doesn’t have a locking center differential.
This says it does: http://models.audiusa.com/q5/detailed-specifications
Front Differential
Hypoid gear, electronically locking (EDL)
Center Differential
Self-locking differential providing automatic and variable front to rear power proportioning
Rear Differential
Hypoid gear, electronically locking (EDL)
@Sajeev
I think the self-locking bit comes from the Torsen centre LSD. IIRC, it won’t lock properly if one of the wheels has 0 traction.
And if it won’t lock properly, that explains everything. Nice job Audi!
Torsen describes it as a “locking effect,” rather than a locking diff.
It’s a limited slip, in actuality, and as you can see from the demonstration, it works until it doesn’t.
Hmmmmmmmmm… How would an old 1st Gen Santa Fe or an AWD Ford D3 platform do?
Driven like and idiot and on the wrong tires? About the same.
The quattro system has open differentials front and rear. Audi uses the ABS system to simulate a limited slip differential with their Electronic Differential Lock. The quattro system has a drawback though, where one wheel that has completely lost traction (wheel in the air or one CV joint not connected) will cause the vehicle to be stuck. The old ’80s Audis had a manually locking rear differential to get out of such jams.
This looks like a problem (yet another problem) speed would solve.
I can see how this might happen, but I agree that the test is so divorced from reality it’s useless. Maybe, maybe if you go stupid places with exactly the wrong kind of tires, sure, but in those cases you’d be sliding into trees. If you regularly encounter situations like this (I used to, a lot) the “Nuggeter” is right, roll back, get traction, go forward and, for pete’s sake, don’t stop. Why they’re stopping at various stages I cannot fathom.
I’ve beaten situations like this in a front-drive Saab 9-3 with spike spiders and good winter tires, by the way. And spike spiders are a hell of a lot cheaper than a new all-wheel drive crossover.
I disagree. I used to run into this particular situation every time I pulled into my driveway in Vermont.
I had a dirt driveway (like most people do there). You’d plow it when it snowed, but because it was dirt, you’d eventually wear ruts into it, and the snow would fill the ruts and freeze. It was fine for a while, but eventually, you’d get a warm day and some rain and the snow in the ruts would turn to ice, then refreeze when it got dark.
I had a Saab 900 with studded snows that wouldn’t climb it without a healthy dose of sand and salt. And because there were trees on either end of the driveway, which sat at a 90 degree angle to the road, and there was a pretty steep incline, you couldn’t gather a lot of momentum to get up the drive.
Many a night, I left cars, SUVs, trucks, what have you stuck halfway up that driveway.
psarhijinian said “…the test is so divorced from reality it’s useless.”
VespaFitz said “I used to run into this particular situation every time I pulled into my (dirt) driveway in Vermont.”
You two need to compromise. The test is useful for that incredibly small percentage of customers who have steep driveways and no access to snow shovels, snow blowers, de-icing chemicals or sand and lack the ability to walk up hill due to disability or customers who live in the country and get ruts in their dirt driveway.
The only group that needs to be really worried are the folks who’ve got rollers installed at the bottom of their driveway. They’re screwed if they want an Audi.
Of course you can shovel, sand, or park at the bottom of the hill. What they’re selling here is the luxury that you don’t have to. Or for most buyers, that you wouldn’t have to if you actually had a driveway like that. Peace of mind is every bit as real a feature as actual metal.
I disagree here. This test does have a simple value. It proves that the Audi system due to the lack of a locking center diff cannot transfer torque.On the contrary if you put a simple small obstacle in front of one of the Audis tires on a flat surface in a slippery condition forcing the front axle to spin, the rear axle will NOT push the vehicle over it.
This test mock up seen here in the video is a standard torque transfer test procedure used amongst AWD vehicle manufacturers.
aspade replied: “what they’re selling here is the luxury that you don’t have to.”
Actually, I think you have just described the unrealistic expectations of some buyers.
No car or SUV can climb a steep, near zero traction surface, like a completely iced over driveway with no dry patches what so ever. There is a system to overcome those conditions; its called a winch.
If you have patches or bands of ice on your steep driveway, you might do fine in the Audi unless you are dumb enough to find the ice and then come to a complete stop with both wheels of one axle on the ice. If you do that, then yes, the Audi probably won’t make it up.
Anyone who thinks that they can go anywhere/do anything because vehicle has 4WD/AWD is a fool and worse, a danger to themselves and others on the road.
This test mock up seen here in the video is a standard torque transfer test procedure used amongst AWD vehicle manufacturers.
Yes and no. The key point is that they pretty much halted the Audi in the slope at exactly the point it would be trapped. It would be equally facetious a test if Lexus ran the BMW over a rock that snagged it’s undercarriage while the GX470 went right over. Yes, it’s a “standard test of ground clearance”, but you still drove one car in an intentionally boneheaded fashion that very few people would ever try. The next test, of course, would be driving into a five-foot-high garage in either of these cars, and then trying the same in a station wagon.
I can see ways where you could get into this situation, but you would also be a damn fool for doing to unprepared in the first place as it’s not like these conditions are unheard of in areas where they occur. You’d be even more of a fool for driving in exactly the right way to get stuck.
For example, if your driveway is like this, you probably have good snow tires and/or chains and/or sand and a shovel and/or a Lexus GX. I mean, it’d be nice if your Q5 or X3 on all-seasons could tackle this kind of stuff, but even before you tried to make it up an icy hill you’d have slid off the road and/or through a red light and into traffic because of the pedestrian tires you’re running.
I feel strange saying this as I generally am a proponent of electronics and technology saving people from idiocy, but this is such an disingenuous test that I can’t forgive it.
I also have a driveway that would highlight the Audi’s limitations. Steep uphill, lots of ice and zero room at the start to gather up speed. Sure good Winter tires would improve any vehicles abilities but, all things being equal, these demonstration results seem significant.
I’m curious… Which is cheaper?
Installing a driveway heater at the base of your driveway, or buying and running a vehicle that can overcome the frozen base of your driveway?
Since the Audi’s front wheels were spinning and the rear wheels were stationary it’s pretty obvious that it does NOT have a true locking center diff regardless of the advertising hype.
Touche! (Assuming the unseen, far side, wheels weren’t both spinning away, that is)
But even assuming only a marketing locker in the center, why wouldn’t traction control simultaneously brake BOTH wheels on a spinning axle, transferring torque to the opposite one?
I’ll tell you one thing that test is; A snoozefest.
From one “Hogan’s Heroes” fan to another, they’re hoping the average Joe “knows nothing“! Otherwise, I agree that most, if not all cars ads and ads in general are full of so much misleading infromation and that’s being extremely polite. I take all these sort of ads, especially Jeep ads with the proverbrial grain of salt. Although I owned a Jeep Wrangler, and it was very capable, still, you shouldn’t believe what you see and hear!
There have been similar tests conducted that tout the supremacy of Subaru’s AWD system.
http://www.youtube.com/watch?v=ooQRxlChvMw&
http://www.youtube.com/watch?v=Q7dVFY5CxT0&
And this one:
+1
I love my Subaru…
One thing’s apparent in this video…the Bimmer’s diesel is much noisier than the Audi’s.
Of course BMW makes a show of how much better their cars are than Audi’s Looking forward to the Audi film showing how bad BMWs are.
Correct me if I am wrong, please, but a Torsen differential cannot compensate if one of its two driven axles has no friction/resistance. The spinning wheel just keeps spinning.
For Audi to have a non-locking center Torsen makes little sense as there are definitely real-world situations similar to that ramp (front or rear wheel pair loose traction). I got caught in one while driving a Malibu MAXX up an icy hill. Backing down was impossible as there were at least 10 cars behind me and one in front of me, all stuck with various wheels spinning.
For those of you living in continually sunny, dry areas, sure, this is boring as hell. For us folks who drive in the snow, knowing these differences matter as getting stuck’s no fun whatever.
BTW, Subaru’s system’s similar to BMW’s, and while not super elegant, it does work getting vehicles around in occasionally snowy Portland OR.
“For us folks who drive in the snow”
Portland, OR gets an average total snow accumulation of 6.5″ per year. How do you survive such brutal conditions? (Sorry, but you tee’d that one up…)
…..BTW, “average” means little if the years a driver is living there get hit with greater than normal snow levels (as it did for me here two years ago, when it lasted well over a month and kept roads rutted icy messes for several weeks.).
I know what you mean. I live in Seattle. Just one inch of snow sends the city into total shut-down mode, and it’s not because “people here don’t know how to drive.” It’s because all the roads are constantly packed with bumper-to-bumper traffic, we have no plows, and the terrain is mostly steep hills. If even one person makes a mistake and gets stuck, the road gets backed up for miles.
The truth is, stop-and-go traffic on steep snowy hills is a reality some of us face (which is why we own a Subaru.) So everyone saying that this is an unrealistic situation is just plain wrong.
“this 100:0 or 0:100 ratio cannot happen in the Audi.”
Doesn’t the fact that all the power is going to the slipping wheel in this demonstration prove that wrong ? If even 10% of the power was going to the rears then it should inch through the course.
It looks very much to me like an open diff situation. I would say the traction control must have been disabled as it’s main purpose is to prevent wheel spin and it’s clearly not working here.
My steep driveway has a set of rollers installed near the bottom and now I’m afraid to buy the Audi pseudo-SUV I’ve always wanted. What if there’s a blizzard and I can’t pick up my dry cleaning? WE’RE ALL GOING TO DIE!!
Every post about any SUV, real or pseudo, seems to usually devolve into approach angles, locking diffs and suitability for rock trails. We’re not contesting the Camel Trophy, people, we’re driving to the grocery store on paved roads.
I’d also like to thank BMW for correcting my incorrect belief that the best way to get through slippery conditions is not to maintain momentum, but instead is to find a slippery spot and come to a dead stop, then continue forward. Brilliant!
Its good to know that BMW’s pseudo-SUV has got an advantage over Audi’s pseudo-SUV. (Yawn.)
It seems as though they precisely measured the distances and angles to put the Audi into an unrealistically impossible situation. Even if the BMW’s AWD system were better than the Audi’s (more realistic tests would provide some further insight on this), the goal of this “test” seems to have been making the Audi look bad rather than demonstrating any of the BMW’s actual abilities.
You’d be whistling a different tune if you had rollers installed at the bottom of your steep driveway. There have been several times (not once, several) that I have had to park on the street and walk up the driveway to my house!
When I was at the Audi dealership the salesman never even told me that the Audi isn’t engineered to overcome rollers installed at the bottom of hills. Can you believe that!!
I’ll bet a ’41 Willys or a ’48 Land Rover would ace this test. They’d flunk out in the cupholder test though…
Yeah, but I saw a WWII Willys that had a real cozy Tommy Gun holder mounted on the dash that could be accessed by the driver real quick!
I agree. Our 1970 Wagoneer mastered Ohio snow and Hatteras sand with never a slip.
I’m not sure about the ’48 Land Rover Series I but I have a 61 Land Rover Series II and it wouldn’t pass this test due to it’s open differentials front and rear. This despite the fact that it will walk away from either of those vehicles off road. I own a 2007 X5 with the same x-drive as the X3 in the video and while it is excellent on road, I suspect the system would over heat if it was asked to continually engage.
Actually you’re quite wrong, because a Series Landrover (Ie a 1 2 and most 3s) does not have a centre differential. Assuming you’re in 4wd, the transfer box splits torque equally between front and rear axle no matter what the condition.
Regardless of having open front and rear diff, an old landy would absolutely own this test. An early Range Rover might struggle until you engage the manual diff-lock.
Well now you have me curious, I’m going to have to test this out. Rumour has it that Silvy_nonsense has just the driveway I’m looking for! I’ll just have to maneuver around all the stranded quattro’s at the bottom.
For a wealth of information on all wheel drive systems, visit the All Wheel Drive Encyclopedia at
http://www.awdwiki.com/
2007
There isn’t an all wheel drive that succeeds in all situations. I’ve owned many awd vehicles: 1987 Jeep Cherokee selec-trac, 2001 Audi A6 4.2, 2004 allroad 4.2, 1992 Subaru SVX, 2007 and 2006 Subaru spec.B, and Subaru Outback 3.0 R. The two Audis and the Subarus with VDC have been the best performers. My 1994 Dodge minivan AWD was not so good, probably because it was essentially a fwd that switched to awd under certain circumstances.
The 94 Dodge used a simple VC(Viscous coupling) to transfer power to the rear axle. No diff lock no center diff. As soon as the VC noticed a differential speed between the front and rear axle it tranfered power to rear.But it was a good standard system.
I never had an issue with the Subaru AWD in 5 years of Detroit winters.
OTOH, I wouldn’t ever look at BMW for a winter car, either.
You’re all missing the point. I think Sajeev’s reference to Welch & McCarthy was an obvious declaration that clean, efficient diesel engines are for Communists and shall remain blacklisted from our shores as long as the great Bald Eagle soars above our hallowed land. God Bless Regular Unleaded, and God Bless America.
Thanks a lot. On the bright side, with any luck the Secret Police might be nice enough to put us in the same prison for our acts of automotive treason.
I call top bunk.
I guess ESC was ON in the Audi. Q5 has somekind of special off-road function which also locks the center diff when you press ESC off.
Best modern awd car I have driven is previous generation European market Subaru Legacy 3.0R Spec B. Spec B came only with 6-speed manual from Impreza STI. It had vicious coupling center diff and rear LSD. And the insane thing was that car of this price level in 2005 had no traction or stability control from the factory, it wasn’t even possible to buy it as an option! :) Real drivers car during winter!
Same test track as my my2000 ML320. no locking diff’s on my car, just it’s fancy braking system. It works.
Weak-minded runts can’t understand the concept and/or usefulness of this test setup. Obviously there is a problem with the Audi Quattro system…This has been known for decades in Europe. Most people in the USA buy the Subarus if they want proper AWD traction.
I am pretty sure this Q5’s failing performance has absolutely nothing to do with the AWD system and everything to do with DSG gearbox. DSG gearboxes are known to cause these kinds of issues when driving off-road. They can’t handle any slip and will simply disengage when slip is detected to preserve the clutch pack.
The new X3 is equipped with a conventional 8-speed automatic with torque converter. Handles slip, no problem.
What? That doesn’t make any sense, based on what I know about DSGs. Please explain.
I’m pretty sure I could get up that hill in my run-of-the-mill front-wheel-drive Jetta.
I just wouldn’t stop at either of the rollers. Keep right on going = problem solved.
“Rigged” is such an ugly word. I think “set up and performed in such a way to both take advantage of the strong points of your product while at the same time exposing and exploiting the perceived weakness of your competitor’s product.”
Okay, “rigged” is so much easier to type. Driven properly, my FWD sedan would probably make it over that rig.
Audi has a torsen. Its good because it works very quickly and, in real world situations, is less likely to let a wheel slip and thus you are less likely to get stuck/lose traction. It multiplies torque from the slipping axle to the gripping one but if you happen start the car with an axle in the air, or on rollers, there is no torque to multiply so the other wheels won’t spin. That said, ESC would have applied braking to the slipping wheel thus generating torque to send to the other wheels. I have seen this in my A6. When I first got it I played around after a HUGE snow storm. I turned off ESC and was having fun power sliding in a parking lot. With the ESC off the A6 easily powered through the thick snow with no nanny stealing my fun, it was a hoot watching all 4 tires kicking snow all over the place. BUT, once I stopped on ice, the car had a hard time getting going, rear wheels spinning. While they were spinning I turned on ESC and you could literally feel the rear wheels getting braked and at the same time the front wheels started spinning because there was now torque to multiply from the braked wheels. I can believe this test, but they had the ESC in the Audi turned off.
Ahh, so that is how Audi works around the Torsen.
Is this true for all Audis using a Torsen as center differential?
BTW, a comparison of an Audi Q7 to BMW and LEXUS showed the Audi getting out of a 3-wheel spin situation, but slower than the Xdrive. The LEXUS went nowhere.
The next Gen Quattro has some differences and a vectoring system, pretty sure there is no locking diff……BUT a locking diff is for off-road use. The Torsen system is preferred in sport cars as it is not based on slippage but torque. Therefore works very fast and avoids the wheels slipping in the first place. So getting out of a slipping situation is great, even better is not getting into one in the first place. A locking diff would hurt a sports car in dry conditions by increasing wheel spin. So Torsen-based systems are generally better in sport driving situations. But this test is between SUVs….and as brock said, the Audi has a button that will lock the diff for you when you are not tearing around on dry pavement. They never used it, or ESC, in the video.
While the video may or may not be deceptive about the relative merits of the Audi vs the BMW, it’s a fantastic way to educate about the role played by differentials. Not that the best and brightest need it – but among the general public, what percentage of people who drive 4WD vehicles would even know what a transfer case is?
Also Vt, also Steep driveway in the shade most of winter, gets quite icy. I have no trouble getting up it with my Elantra. It does have traction control, more importantly it has studded tires….mostly to deal with my driveway. One night I heard screaming tires in the driveway. A neighbor tried to turn around and went a little to far in. By the time they creeped down far enough to find traction they were quite well stuck.Frictionless surfaces existing only in physics class questions, two scoops of sand and a lot less right foot got them out. I Don’t fault their car (an AWD Passat as it happens) I fault the all season tires it was wearing. My wifes Wrangler has no trouble with the driveway in 4WD with its all season tires, but that certainly doesn’t mean its a more refined/safer/better vehicle at anything other then what its built for. In fact if the equation is VW = Audi and Jeep = BMW I’ll try to be aware of the specific circumstances that are problematic and take the….. Ok I’ll take any of the three over the Jeep for anything requiring driving on roads with less then 5″ of anything other then air on them.
Round two: snow race track, S4 vs. 335xi. Let’s see that smug smile wiped off BMW’s face.
At least they did the test on an incline. Systems to deal with wheelspin are typically tested and demonstrated on something called the “elephant’s feet”, which consists of alternating lumps that cause vehicles’ diagonally opposite wheels to be loaded, then unloaded. The trouble with the test is that it’s always on level ground. Of course the systems work then.
In the real world, this sort of unloading often happens on steep driveways. In our part of the world, disused logging roads are kept from washing out by digging drainage ditches diagonally across them. The steeper the hill, the more and deeper these ditches. And they are exactly the situation that utterly defeats open differentials and poses problems for drivetrains with slip limiting gizmos.
Yes, limited slip differentials, lockers and ABS-based traction control systems can deal with this. Up to a point. The “tighter” a limited slip, or the more aggressive the setting on traction control, the more the forces on the driveline approach those resulting from using lockers. To limit the mileage penalty of excess weight, limited slip and traction control systems are tuned to slip before breaking driveline parts. The result is that permitted wheelspin gets more likely the steeper the hill and the more uneven the wheel loading. Just imagine how robust driveline parts would have to be if a vehicle was capable of pulling itself up a steep hill with power to only one wheel. Those who have 4×4’s with three lockers don’t have to use their imaginations.
Also, ABS-based traction control systems are designed to “let go” after a certain duration of high throttle, to protect the brakes against overheating.
And yet another observation. The “tighter” a differential, the more it will resist the different rates of wheel rotation when a vehicle corners. So “tight” differentials contribute to wheels breaking traction while cornering on slippery surfaces at, say, highway speeds. People who lock up differentials on their suv’s for “extra” traction on slippery highways often end up having unplanned off-road excursions at the first corner. This sort of thing is another reason why drivers would benefit from knowing more about drivetrain dynamics.
I regularly drive a current generation Suzuki Grand Vitara up and down steep icy/snowy, mountainous, outsloping, disused logging roads. Just today, I drove a 3000′ climb/descent on hard packed snow and refrozen ice, at around the freezing point. Fortunately there were no crossditches. Comming in handy is another factor that is NEVER mentioned in discussions of vehicle suitability for slippery conditions. The Grand Vitara happens to have perfect weight distribution between all four wheels. Even wheel loading equalizes forces on the drivetrain components, and so limits the problems the traction control system has to deal with.
From the wiki about X-Drive:
“The front and rear differentials in xDrive vehicles are an open differential design, thus relying on brake application by the DSC system to transfer power from the slipping wheel to the wheel with traction.”
So if DSC was tuned off, like ESC was obviously turned off in the Audi, the bimmer would do the same thing. Nice try.
Probably not, this test is about transfer from front to rear (and vice versa) where it doesn’t matter whether there is an open diff on either of the axles.
“the Bimmer has a transfer case that automatically varies front to rear power distribution via clutches and gearbox fluid”
This should work with or without DSC.
Knew I would find it. A test of a quattro audi on 4 rollers with EDS (a component of the current Audi ESC) turned ON. Notice how all 4 tires spin. BMW turned off ESC in the Audi in the video above.
This video definitely shows side-side traction is working (EDS brakes the spinning wheels (or locks front/rear diffs) and traction is provided to opposite side).
Doesn’t confirm front-back works different than the above video shows, though. Key is finding a statement that the Audi center diff has some sort of clutch pack or anti-slip system.
BTW, top of line Subaru Outbacks also uses a center diff, but combines it with a clutch pack to minimize the problem open diff causing Front-Back wheel spin. Lesser Outbacks make do with just the clutch pack.
It could be the BMW system “lets go” at a higher level of uneven forces than the Audi’s, with both having the TC and ESC systems turned on. And maybe that’s all there is to it.
On ice, my A6 clicks on the ESC as soon as I touch the pedal. If I FLOOR it on sheet ice, like the lady in the video did, all 4 wheels will stop and start jerking, trying to gain traction. They don’t spin. Its a false test. Some dealership in the states did a similar “test”. If it was true, you would think BMW would have it on TV. But all the “Audi on a roller clips” I have seen were made by dealerhips and fanboys. Nothing official. If this was true, and Audi did that on rollers with ESC and all the electo programs on, BMW would have a national ad campain about it. But they don’t, because its not true.
I think the reason they disabled the TC and ESC is because no self respecting butch-mobile owner would ever allow “nannies” in their car.