The state of the internal-combustion art has never been more artful. Direct fuel injection, variable valve timing, computer-controlled ignition systems and a hundred other technologies have become tools for shaping how an engine performs. Engineers can add torque here, subtract it over there, let the engine rev at one point and hold it back at another. This is a new artistic medium, and Audi's latest V-8 engine is a masterpiece.
Called the EA824 inside Audi, and marketed as the 4.0 TFSI V-8, it's a densely packed engine less than 20 inches long that overachieves relative to its 4-liter displacement. TFSI stands for Turbo Fuel Stratified Injection, and right now internal combustion doesn't come better than this.
I drove two 2013 Audis equipped with different versions of the EA824. In July, my nephew and I took the large 520-horsepower all-aluminum S8 sedan ($125,995 as tested) on a blitz from Dallas to Oklahoma and across the Texas panhandle, all the way home to Santa Barbara, Calif.
Then, a few weeks later, my wife and I drove the slightly smaller, sleeker, steel-body 420-horsepower S7 ($94,570 as tested) up the California coast to San Francisco and back.
On the long, often empty, straights of Interstate 40 across the Great Plains, the S8 was outrageously serene. As we cruised through sudden cloudbursts, surprise hailstorms and blistering heat over three days, it pushed forth with only slight differences in tire noise to indicate whether we were moving across water, ice or broiling asphalt. Even on lonely stretches of open road, as our speed crept inadvertently toward three digits, there was barely a change in the wind's whistle. This is Audi's most capable and powerful large sedan, and it is built to ingest continents.
The family of A8 sedans, of which the S8 is the highest performer, includes standard and stretched L versions (with wheelbases of 117.8 or 122.9 inches), with powerplants ranging from a turbodiesel V-6 to an outrageous 6.3-liter 12-cylinder. All of the A8s and the S8 are built with an all-aluminum space-frame structure that has been the car's hallmark technology since the first-generation sedan of the mid-1990s.
The high-style, low-slung S7 has a predatory countenance. There's something empowering about simply ducking under the low roof and into the thickly bolstered driver's seat, as if you've transformed from a weakling into a Charles Atlas muscleman without all that pesky weightlifting.
But the S7 is a more conventional machine than the S8. It's a hot-rod version of the A7 hatchback, which itself is a derivative of the more upright A6 sedan. The structure is ordinary steel and the 114.7-inch wheelbase is the same as the A6's. Unfortunately, the S7's squashed but stylish fastback roofline compromises headroom, and the rear legroom isn't impressive either.
Regular A7s are available with the same turbocharged diesel and supercharged gasoline 3-liter V-6s that are found in the A8. But new for 2014 is an even more radical RS7 that uses a version of the EA824 rated at a loopy 560 horsepower. With a base price of $105,400, it starts out $25,200 more expensive than the 2014 S7.
That's $25,200 that could be used for other important things. Like bail.
Slicing through central California, where the weather is always perfect, I swear that my wife's pupils dilated noticeably when she first dipped into the S7's accelerator pedal. The S7 may give up 100 horsepower to the S8 -- at least according to Audi's suspiciously conservative ratings -- but 420 horsepower is still some 2.4 times the rating of her Kia Sorento. Power may be corrupting, but it's also empowering, liberating and fun.
Forget all the navigation systems, radar-controlled cruise systems and even the Wi-Fi connectivity built into both the S7 and S8. All that is stuff you can find in other luxury performance cars. Other manufacturers are even adopting all-wheel drive similar to Audi's once novel but still brilliant quattro system. What those other cars don't have is the EA824.
The most distinct element in the EA824 is its reverse-port cylinder heads. That is, the exhaust ports for the engine are aimed into the V-shape valley between the two banks of cylinders with the intake ports on the outside. While this is opposite of how most other current V-8s work, it isn't unprecedented. Various V-8 and V-12 engines purpose-built for racing have been similarly structured.
By placing the EA824's pair of twin-scroll turbochargers in the V-8's valley, Audi effectively plumbs them directly into the exhaust ports. That ensures that the turbos can spool up to an effective speed more rapidly; there is no lag in the throttle response.
That trick setup combines with the precise fuel and air metering made possible by direct injection and variable valve timing to let the engine run with both relatively high compression ratios and high boost pressure.
Motor Trend magazine put an S8 on a chassis dynamometer -- a set of weighted rollers used to measure power output at the tires -- and found it making 479 horsepower at just over 6,300 rpm. Figuring a 20 percent parasitic loss between the engine and the tires, that puts the true crankshaft output at 575 horsepower. The EA824 in the S8 is a beast, and the S7's is only slightly behind.
In the S7, the engine is backed by a 7-speed automatic transmission and quattro all-wheel drive. Left to shift by itself, the transmission lets the engine loaf at low speeds during part-throttle cruising. On top of that, when demand for power is low, half of the cylinders are deactivated to reduce fuel consumption further. So even though this is a car that, according to Motor Trend, will slam from 0 to 60 miles per hour in only 3.9 seconds, it is also rated at 17 m.p.g. in the city and a noteworthy 27 m.p.g. on the highway.
Beyond the engine performance, however, the S7 is quiet most of the time, composed all the time and utterly tenacious in its grip of the road. The interior is elegant and feels less cramped than other low-roof four-doors, and most of the controls make intuitive sense most of the time.
Think of the all-aluminum S8 as a starship with an 8-speed automatic transmission. According to Motor Trend, it blasts to 60 m.p.h. in an otherworldly 3.5 seconds. But there isn't a vicious molecule in this car; it all works so casually that you feel it could be operated by a shrug of the shoulders. The steering is instinctive and informative, the huge brakes seem as if they could stop the universe from expanding and the car rips through bad weather as if it were itself a tornado.
If the S8 isn't the quickest sedan currently available, it's one of the top two. According to Motor Trend, the 550-horsepower $200,000 Porsche Panamera Turbo S matches the Audi's 3.5-second 0-to-60 time and its 11.8-second quarter-mile run. Compare that with the 540-horsepower BMW Alpina B7 and the 621-horsepower Mercedes-Benz S65 AMG, which both require an entire 4.3 seconds to hit 60 m.p.h. That's an eternity when you're racing other titans of capitalism up and down Wall Street.
Beyond that, the S8 is more accommodating and comfortable than Porsche's sedan and also much more nimble than either the BMW or Mercedes.
The S7 is quicker than its competition, too, and easier to live with. And it's at least as good-looking as the BMW 650i Gran Coupe and the Mercedes-Benz CLS550.
But the most attractive alternative to the S7 is actually its more conservative brother, the S6. Mechanically, the S6 is virtually identical to the S7, but it is roomier on the inside. It may not have the S7's blousy, brazen sex appeal, but it has a $6,800 price advantage before options.
Like all the cars they compete against, the S7 and S8 are overstuffed with technology and overwhelmingly competent. But so what? What these cars have that's special is their soul, an indomitable, artful character that transcends engineering.
This article originally appeared in The New York Times. First Published October 19, 2013 2:01 PM