Piston Slap: Have You No Sense Of Decency Sir, At Long Last?"

Sajeev Mehta
by Sajeev Mehta

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.

Sajeev Mehta
Sajeev Mehta

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  • Brandloyalty Brandloyalty on Dec 06, 2010

    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.

    • Frizzlefry Frizzlefry on Dec 07, 2010

      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.

  • LimpWristedLiberal LimpWristedLiberal on Dec 07, 2010

    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.

  • TheMrFreeze That new Ferrari looks nice but other than that, nothing.And VW having to put an air-cooled Beetle in its display to try and make the ID.Buzz look cool makes this classic VW owner sad 😢
  • Wolfwagen Is it me or have auto shows just turned to meh? To me, there isn't much excitement anymore. it's like we have hit a second malaise era. Every new vehicle is some cookie-cutter CUV. No cutting-edge designs. No talk of any great powertrains, or technological achievements. It's sort of expected with the push to EVs but there is no news on that front either. No new battery tech, no new charging tech. Nothing.
  • CanadaCraig You can just imagine how quickly the tires are going to wear out on a 5,800 lbs AWD 2024 Dodge Charger.
  • Luke42 I tried FSD for a month in December 2022 on my Model Y and wasn’t impressed.The building-blocks were amazing but sum of the all of those amazing parts was about as useful as Honda Sensing in terms of reducing the driver’s workload.I have a list of fixes I need to see in Autopilot before I blow another $200 renting FSD. But I will try it for free for a month.I would love it if FSD v12 lived up to the hype and my mind were changed. But I have no reason to believe I might be wrong at this point, based on the reviews I’ve read so far. [shrug]. I’m sure I’ll have more to say about it once I get to test it.
  • FormerFF We bought three new and one used car last year, so we won't be visiting any showrooms this year unless a meteor hits one of them. Sorry to hear that Mini has terminated the manual transmission, a Mini could be a fun car to drive with a stick.It appears that 2025 is going to see a significant decrease in the number of models that can be had with a stick. The used car we bought is a Mk 7 GTI with a six speed manual, and my younger daughter and I are enjoying it quite a lot. We'll be hanging on to it for many years.
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