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