2007 Audi S6 vs. BMW M5, M-B E63 AMG
Bullet Sedans Reloaded: High-caliber ballistics for the spirit. From Germany, with liebe.
TONY SWAN
From the February 2007 Issue of Car and Driver
These are the sedans that stir men's souls. Yeah, yeah, that's not quite what Thomas Paine said in 1776. But if he'd been with us while we were putting this threesome through its paces, he might have been tempted to devote his literary talents to something other than revolutionary pamphleteering. Might even have signed up for a blitz course in German, to put a finer point on the subtleties of these four-door bullets.
The German language would certainly be appropriate because, when it comes to sedans capable of simultaneously indulging a driver's hedonism and transporting the spirit, nobody does it better than the denizens of Deutschland. Is it the influence of the autobahn, which continues to be the world's most demanding high-speed-driving development crucible? Or the handling demands of the Nürburgring's Nordschleife, the fabled circuit used by German carmakers to test their cars, a track that magnifies any dynamic shortcoming a car may have.
In a word, ja.
The names here will be familiar to faithful readers — Audi, Mercedes, and most particularly, the BMW M5. Since the arrival of the first M5 20 years ago, this Bimmer has been the benchmark in luxury sports sedans and as such has been the centerpiece in four previous comparison tests, where it has prevailed three times, including a first place in another three-way duel just over a year ago "Bahn Burners, Episode 39," [C/D, January 2006]. That M5 was fresh off the boat, giving us a first opportunity to record formal test data with BMW's new V-10. Another M5 carried your humble narrator to an easy luxury-sedan class victory in the 2006 running of One Lap of America, and even though we carped about the irritating quirks of the sequential manual gearbox, it was hard to imagine some other contender upending the champ, particularly this early in its latest renewal.
But the status doesn't remain quo in this high-powered game for long, and soon we found ourselves planning yet another bullet-sedan, uh, shootout. BMW had yielded to the persistent U.S. market clamor for a manual-transmission option for the M5, Audi had added V-10 power to the A6, yielding a new S6, and AMG had massaged the new Mercedes E-class, creating an E63 AMG.
With November grays and snow squalls descending on Ann Arbor, we arranged to rendezvous with our three superkrauts in L.A. From there we rumbled up to Willow Springs, in the high desert near Edwards Air Force Base, for instrumented testing, then spent the next two days on gorgeous back roads to and from Monterey, a trek that included the 137-mile run down California Highway 1, a collection of curves, cliffs, and Pacific views that has few equals anywhere.
When the brake pads cooled and the ballots were tallied, there were surprises, and a verdict that was not quite unanimous. But if we differed on who's No. 1, we were united on this: In the world of bullet sedans, it's still Deutschland über alles. In this rarified price-and-performance category, any member of this Teutonic trio is superior to anything offered by anyone anywhere else.
You've heard the old maxim about being careful what you wish for, and here's another vindication for its persistence. When the latest M5 came along, we were properly awed by its 500-hp V-10 but critical of its seven-speed sequential manual gearbox (SMG), an automated manual transmission. On a dry racetrack, its lightning shifts are beyond reproach. But on public roads, in full automatic mode, it's a different story, with big lags between upshifts. A logbook commentator reported that he "tried to leave it in auto mode but just couldn't stand it."
So BMW responded with a six-speed manual-gearbox option, which we've been anticipating for a year. Yes! This'll push the bad-boy Bimmer a big step closer to perfection. We thought.
Uh-oh, not so fast. This M5's shift-for-yourself six-speed is consistent with others we've experienced from BMW. In fact, it's the same six-speed employed in the previous-generation M5. And therein lies the rub. The new M5's V-10 was designed to be allied with the seven-speed SMG. Bolting the same engine to the six-speed entailed a proviso. With the SMG, the driver had the option of disabling the dynamic stability-control (DSC) system. When you opt for the manual, you don't get that option. A little dashboard button labeled MDM — for "M Dynamic Mode" — raises the DSC intervention threshold, but unlike the SMG version, it can't be completely shut down and is always on guard. When wheelspin is detected, DSC goes to work, damping the throttle, sometimes squeezing the big cross-drilled brake rotors.
Would you be surprised to hear that this doesn't have a positive effect on acceleration? Or lap times on the Streets of Willow? Or making a hot exit from a slow corner? Of course you wouldn't. Because that's precisely what happens. This M5 was a half-second slower to 60 mph than the SMG version we tested in January 2006 — 4.7 versus 4.2 — and a half-second slower through the quarter-mile: 13.0 seconds at 114 mph versus 12.5 at 118. DSC also inhibited lane-change performance (60.8 mph versus 65.6) and skidpad results (0.83 lateral g versus 0.89).
All of this is attributable to product-liability issues, specifically, concerns about axle tramp, a.k.a. wheel hop, during full-throttle launches, which could break expensive drivetrain bits and irritate the well-heeled owners BMW would prefer to keep happy.
On the other hand, when those owners want everything their M5s can deliver, DSC's relentless vigil is going to be pretty irritating, too.
There are other M5 elements that aren't exactly endearing. You might expect another iDrive diatribe here, an expectation we could cheerfully fulfill, but we'll confine ourselves to saying that this maddening secondary-control collective is still a good reason to consider another car. Beyond that, we recommend avoiding the $1900 multifunctional bucket seats with their movable torso bolsters, which deliver low-speed, high-torque hugs at the slightest hint of lateral g; we think the steering, although accurate, underdoes the power assist at high speeds; the cowl height is high compared with the two other cars', inhibiting forward sightlines; there's a shortage of small-object storage in the cockpit; and the as-tested price, tops in this test, is intimidating.
At core, this M5 has the same virtues as its predecessors — fluid responses, superb brakes, abundant power, athletic good looks, and the grace of a gazelle. But this particular gazelle isn't quite up to pacing the herd.
Hey, what's up with this? Second place, and crowding the Benz for first? We're just as surprised as you. On paper, the S6 didn't figure as a top contender. At 435 horsepower, its engine output trailed the Bimmer's and Benz's by a bunch. Its curb weight — 4540 pounds — was highest by a substantial margin (the inevitable consequence of all-wheel drive), and pretty much every millimeter of its 5.2-liter V-10 engine hangs out beyond the centerline of the front axle, yielding a 59/41 forward weight bias.
Not to put too fine a point on it, but this isn't an ideal prescription for agility. Yet that's precisely what the S6 delivered. Some logbook comments: "I'm astounded at what a cool operator the S6 is on the track." "Really fun and confidence-inspiring in the twisties. I'm not sure if I'd have more fun in a 911 on some of these stretches."
The S6 surprised us by laying down a lane-change speed that was a mere 0.2 mph off the best (although speeds of all three cars were close), followed that up with the best skidpad number (all the cars wore low-profile Continental ContiSportContact2 tires), and then really won our hearts during the two days of challenging back roads that followed track testing. Unlike the Audi S8, the S6 rides on conventional steel springs, with a multilink suspension and hefty anti-roll bars at both ends. The bars kept the Audi's cornering attitudes impressively level and also allowed the suspension guys to keep the spring rates relatively civilized, which paid off with all-day ride quality.
The S6's feline responses were magnified by its speed-sensitive power rack-and-pinion steering, which was quick — just 2.5 turns lock to lock — light, and accurate to thousandths of an inch.
The Audi stacked up well in nondynamic virtues. Its seats, for example, edged those in the Benz and Bimmer for support and comfort, although the edge in this department was wafer thin. But the S6 did hold a clear ergonomic advantage and got top marks for styling, inside and out. We were also impressed by the window sticker: The base price was $13,455 more attractive than that of the E63 and $12,875 lower than the M5's, and the as-tested disparities were even bigger: $14,385 better than the Benz's, $19,270 lower than the BMW's.
So why didn't the S6 top our charts? It nearly did, but in the end it lost out in a power struggle. The irony is that all hands were impressed with the Audi's 5.2-liter DOHC 40-valve V-10. As an aside, here's Audi's official party line concerning this powerplant: It is not the Lamborghini Gallardo V-10. Hey, check the displacement: 5204cc compared with 4961. Check the output: 435 horsepower versus 512; 398 pound-feet versus 376. No similarities, right? Yeah, right.
Be that as it may, for all its thrust and a celestial exhaust note, the Audi's not-a-Gallardo V-10 was upstaged by the Benz's superb AMG V-8, trailing the Stuttgart missile by substantial margins in every acceleration category. That, plus a paddle-shift six-speed manumatic that tended to make its own upshift decisions, kept the S6 off the top step on the podium.
Still, if money is important — when is it not? — and nosebleed thrust isn't absolutely essential, this Audi delivers an unbeatable level of fun for the euro.
A few months back, we matched an E550 sedan against three other hot sports sedans ["Faster Horses," C/D, November 2006] and emerged with a mixed review. It was the first comparison test involving the latest E-class, and even though the test crew was properly impressed by the new 5.5-liter V-8 and appreciated the car's serene deportment on the open road, its new Airmatic suspension, with adaptive damping, delivered sluggish responses on the hills and curves of our Hocking Hills test loop in southeastern Ohio.
Checking the specs prior to this California confrontation, we wondered if we might be looking at a repetition of that test, albeit at a considerably faster pace, thanks to the E63's superb new 6.2-liter AMG V-8. (AMG calls it 6.3 liters, even though the displacement is 6208cc, a tribute to the magnificent 300 SEL V-8 of the late '60s. Think of it as revisionist arithmetic.)
Historically convenient addition or not, there was certainly nothing disappointing about the E63's power. AMG has long since discovered that massive thrust pleases its customers — no surprise there — and can also cover for so-so handling. Not to mention making short work of dicey passing situations. Although it's not a torque monster like the supercharged 5.4-liter V-8 that powered the E55 AMG — 516 pound-feet — the naturally aspirated 6.2-liter is no lightweight in the grunt department, generating 465 pound-feet, and it makes lots of horsepower: 507 at 6800 rpm versus a mere 469 for the E55.
Paired with the Mercedes seven-speed automatic, the AMG V-8 delivers 4.2-second 0-to-60-mph runs and covers the quarter-mile in 12.6 seconds at 115 mph — about the same as the E55 AMG, even though the E63 weighs in some 80 pounds heavier. The seven-speed automatic has a paddle-shifted manumatic function that really knows how to follow orders, no independent decisions, unlike the Audi's six-speed auto. As an aside, we have a confession to make: As much as we like the sense of involvement that goes with a good manual gearbox, we have to admit that the latest manumatic and automated manual transmissions are pretty compelling, particularly allied with big-output powerplants such as the ones under scrutiny here.
Okay, lots of power, lots of go, no surprise there. But the surprise — a pleasant one — lay in the distinction between the standard Mercedes Airmatic suspension and the AMG-tuned Airmatic suspension. Wow. With the stability control turned off, the Benz could be pitched and tossed and power-oversteered without intervention. Think high-end drift car. Think, as Larry Webster remarked in the logbook, "best Mercedes sports sedan I've ever driven."
The inner Benz was seductive, too, with nicely bolstered seats clad in soft leather, and various other AMG reminders. The relatively low cowl provided the best forward sightlines in the group, and the Benz also drew best-in-test marks for its fit and finish.
There were some small demerits. The COMAND secondary-control collective, although improved in this new E-class, is still complicated and confusing, and the styling, although handsome, seemed a little too reminiscent of the previous generation to some.
But as noted earlier, the Benz's eager throttle response — most of the torque is available by 2000 rpm — made it a superb ally on byways such as California Highway One. If it wasn't quite as unflappable as the S6, it was certainly more willing and able to hurry through twisty sections than any other AMG car in our experience. Which was just enough to carry the day.
And so we await the next day.
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