Audi R8 vs. Mercedes-Benz SLS AMG

Two supercars, both engines warm, both keys in my pocket, both completely at my beck and call. Each costs north of $200,000, one screams with a hyperactive high-revving V10, the other booms relentlessly forward with a torque-laden V8. Their mere presence makes car junkies — of both sexes and, surprisingly, at least in the case of the Mercedes, of all ages — weak in the knees. They’re both brimming with enough high-tech electronics to launch a space shuttle, enough leather to satisfy a serious fetishist. The race track, dry, twisty and beckoning, awaits some serious flagellation. All I’m thinking about isfaced with this cornucopia erotica alldressed up in their laciest to seduce me with theirI, like thecloseted engineerI oftentimes try to denywant to talk than the really, and you can see why I could easily — were I so inclinedtake an evangelical’s vow of celibacy I simply can’t help myself; where you mightsee flowingsilky skin I see centres of gravity and weight distributionIf you’re readingthen you at least know that these cars, though they boast about the same horsepowerthe GT’s tweaked 5.2-litre V10 pumps out 560 ponies;the SLS’ big 6.2-litre V6, 5633.6 and 3.8 seconds to 100 kilometres anhour, respectivelydiffer greatly in their layout. The Mercedes-Benz is the classicallyconstructed gran turismoits engine is in front, the drive wheels are inthe rear and in between are the transmission and driveshaftThe Audi, meanwhile, asits supercar shape suggestsits entire powertrain crowded behind therear of the cabin in one great lumpThe R8 throws in all-wheel drive just to make matters a little more confusing.
the difference between the handling of these twodiffering designs is a result of weight distributionthe front-engined SLS having slightlymore weight47%over the front wheels than the R8 which boasts a 43%/57% frontto-rear weight distributionBut the plot is far more complex andwhile how muchweight is on which wheels is of great significanceit doesn’t totally explain why allmodern supercars have gone to the mid-engined formatyou guessed it, that explanation has something to do with polar momentseach with five-kg weights attheir end. But one places those weights a convenient hand width apart, while the secondhas them separated by a metretechnically, of course, it’s now a barbell Both willrequire the same amount of energy to raise above your head and, put on a scale, theywill both register five kilograms at each endhence a 50:50 weight distributionBut, if you were to try to rotate them, their behaviours suddenly become vastly different the shorter barbell in the middle and it will twist in your hand with littleeffort. Grab the barbell in the middle and any rotation will take far more effortrats,like myself, can try this for themselves. Do an overhead press with a 10-kg dumbbell in your hand and it’s relatively easythe same thing holding a long 10-kgbarbell and see how much more difficult it is to keep it stable over your head
The same applies to cars. If you locate much of the car’s actual weight as close aspossible to the centrethe engineers call this mass centralizationtheoretically the car should be far more responsive to steering inputs, more easily controlled throughcorners and easier to toss from one corner to the next. Move the weight further from thecentre and the car becomes less responsive to driver inputs and less willing to changedirectionThink of it as the automotive equivalent of American politicsThe farther thepolitical discourse moves out to the polar extremesthe more unwieldy the whole enterprise becomes.At least that’s the theoryLike all things theoreticalperfectionmust give way to practical everyday politicsengineeringso just as Audi’s engineis not situated perfectly in the middle of the R8, neither is the SLS’s V8 truly in thefront. That great mass of R8 V10 is actually a little more rearward than perfectlycentralized. Mercedes, meanwhile, has taken great pains to shove its big 6.2-litre V8 as far rearward as firewall and passenger’s feet would tolerateit’s also located itstransmission in the rear it’s called a transaxle but that helps weight distributionmore than polar moment of inertia The question then becomes which of theseimperfectan you spell compromisedesignsfront mid-engineishor mid-with-a-tinge-to-the-rearworks best?
If you were judging just from race track performance, you’d have to give Audi’sengineers their due. Indeed, though the R8even isn’t as stiffly suspendedas single-focus supercars such as the Ferrari 458 and McLaren’s new MP4-12C, it’squite a race track tool. Of course, the grip is fantabulousthe tires are stickyP235/35ZR19 in front and monstrous P305/30ZR19s in the rear the R8’sall-wheel-drive system is tailored toward sporty driving85% of the V10’s torque isdistributed to the rearand the roll well mitigated
But the real joy of the R8 is that it feels like the entire car is rotating about a point directly under your butt. Rather than steering a 4,435-mm-long car, the sensation is that you’re actually controlling something not much larger than the seat in which you’re driving. That’s the secret of mass centralization