Chủ Nhật, 9 tháng 6, 2013

Audi S8: You Won"t Hear It, but You"ll Sure Feel It

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Dan Neil/The Wall Street Journal


Audi S8




AUTOMOBILES ARE complicated machines with dozens of systems that independently affect owner satisfaction, any one of which can absolutely disqualify a car. Take navigation systems. I recently walked away from the spectacular, $300,000 Ferrari FF in a sour mood, all because of the car’s dated, fiddly navi system, sourced from Harman and ignominiously shared with the rest of the Fiat-Chrysler empire.



Never mind the 651-horsepower V12 and all-wheel drive. Never mind the FF’s enslaving looks and wilding cackle. I couldn’t find the nearest sushi restaurant. Damn you, first-world problems.


Photos: Audi S8


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Dan Neil/The Wall Street Journal


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Audi


S8—which I believe is the quickest full-size, five-seat production sedan in all the world, a siege cannon against the walls of imagination—I hope casual readers will forgive some talk of deck height, manifold routing and zero-lift cams in the interests of a larger point.






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Engines aren’t everything, but they are something. And in the peculiar case of the 2013 Audi S8, the magic is in the engine upgrade. Dan Neil reviews the 2013 Audi S8. Photo: Audi.



The S8 is a low-volume (about 8,000 cars globally) performance variant of the flagship A8 sedan. At $110,000 base MSRP, it’s $29,100 dearer than the standard-wheelbase A8 with the regular 4.0-liter, 420-hp V8. Our test car came with more bells and whistles than the Singapore harbor patrol, including a $6,300 Bang Olufsen sound system and an extended leather package ($5,500), which helped balloon the as-tested price to $125,995.



This and that, here and there, it all comes down to an engine upgrade: The S8 deploys Audi’s astonishingly compact EA824, a direct-injection, bi-turbo, 4.0-liter V8 rather turned outside-in, with the exhaust plumbing routed between the 90-degree V cylinder banks, where dual twin-scroll turbochargers and the intercooler reside. The object is to shorten the exhaust paths to the turbochargers, ensuring greater thermal efficiency and response.



Be assured: It’s responsive. This thing kicks like a velvet mule.


The Ferrari-fast S8 eerily combines petrochemical violence and silence.






Let’s go to the numbers: a nominal 520 horsepower (we’ll get back to that) and 481 pound-feet of torque from 1,700 rpm to 5,500 rpm. As compared with the retiring V10, the all-aluminum V8 is 16% more powerful and a staggering 27% more fuel-efficient (15/26 miles per gallon, city/highway), all from an engine that is, for packaging purposes, about a third smaller than the V10. Downstream of the engine is Audi’s smooth, silent, nearly sentient eight-speed automatic transmission, and from there the power is routed through the car’s Quattro all-wheel-drive system with rear sport differential.



AWD cars have an advantage in off-the-line acceleration, being able to put power to the ground with four wheels instead of just two. But few AWD cars have the massive gripping authority, the talons-in-the-tarmac feel, of the S8 in stomp-and-go mode. And when the road gets twisty, the bosses in the back had better hang on to their brisket. The way you get this car around a corner is to be conservative on entry, get the big car turned in, and squeeze the trigger. The S8′s power-on, corner-exiting balance is exquisite. The brakes—15.7-inch front discs of some exotic metallurgy—are, likewise, epic.


2013 Audi S8



Base price: $110,000



Price as tested: $125,995



Powertrain: Twin-turbocharged and intercooled 4.0-liter, 32-valve DOHC V8 with displacement on demand; eight-speed automatic transmission; full-time all-wheel drive with rear sport differential




Horsepower/torque: 520 hp at 6,000 rpm/481 pound-feet at 5,500 rpm (mfr.)



Length/weight: 202.2 in./4,641 lbs.



Wheelbase: 117.8 inches



0-60 mph: 3.9 seconds (mfr.)




EPA fuel economy: 15/26 mpg, city/highway



Cargo capacity: 13.2 cubic feet



So, yes, the S8 is quite able in the corners, but it’s the S8′s straight-line performance that scatters brain confetti to the wind. Motor Trend logged a zero-to-60-mph acceleration time of 3.5 seconds—about as quick as the Ferrari 458 Italia—and a quarter-mile time of 11.8 seconds (118.3 mph). Accelerating from 45 to 65 mph in the S8 takes 1.8 seconds and unleashes such butterflies, it’s like your stomach is hosting an over-the-top wedding.


BMW


Alpina B7. The only four-seaters that can hang with it are the Porsche Panamera Turbo S, the Nissan GT-R and the Ferrari FF, depending on how far you want to stretch your definition of “seats.”



I don’t want you to get the idea the S8 is a loud, scary car. It’s just scary.



Let’s talk noise-vibration-harshness, or NVH. The S8′s cylinder-on-demand system uses zero-lift camshafts that rotate in and out of play in the valve train, depending on load. The challenge for such systems is engine shake, rocking and transient vibration (the same is true for hybrid powertrains in which the gas engine is constantly cycling on and off). The S8′s two active engine mounts consist of electromagnetic coils encased in hydraulic fluid, which themselves impart vibrations 180 degrees out of phase with incoming vibrations, canceling them. The mounts do most of their work between 25 and 250 Hz, in V4 mode, but they also work when the engine is idling. When the S8 is parked, a blindfolded safecracker couldn’t tell if the engine is running.



The Audi is also equipped with what I think I shall henceforth call “active ambience,” a noise-canceling system that electronically muffles undesirable cabin noise with an inaudible out-of-phase signal pumped through the car’s loudspeaker array.



Add to that all the usual noise mitigation one finds in a top-shelf German luxury car—the acoustically laminated glass, the low-drag aero profile, the wads of soundproofing—and you get a car with a really strange, incomputable sensory experience, combining petrochemical violence and silence. It’s a hot rod with a mute button, a de-barked Cerberus, Fay Wray’s silent scream. It’s downright eerie.



At least two publications have dyno-tested their S8 press cars to discover, lo, that the engines produce quite a bit more power and torque than the company claimed. Motor Trend calculated the output to be not 520 hp but a gawdamighty 575 hp, with torque up to 506 (from the official figure of 481).



Of course, Audi would not be the first car company to understate an engine’s output. And this higher set of numbers just makes the EA824 even more astonishing: 575 hp out of 4.0 liters of displacement, while being ULEV-compliant and getting 26 mpg on the highway?



The official explanation is that Audi’s internal testing regime is conservative in order to assure that every last S8 produces at least 520 hp. Audi doesn’t want to deal with owner complaints that the engine is not making the stated horsepower. With the S8, that’s not a problem. Still, the practice is unseemly. How do we know, for example, that it’s not just the press cars that are juiced? It just looks bad for a company with the tagline “Truth in Engineering.”



Lathered in Germanic luxury, impeccably built and deeply handsome, the S8 has so much more to recommend it than just the engine.



But that engine. Oh, brother.


Email Dan at

rumbleseat@wsj.com
and follow him on Twitter
@Danneilwsj


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A version of this article appeared June 8, 2013, on page D11 in the U.S. edition of The Wall Street Journal, with the headline: Audi S8: You Won’t Hear It, but You’ll Sure Feel It.



Audi S8: You Won"t Hear It, but You"ll Sure Feel It

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