A car company's flagship model is usually a very special thing. And when that company is known for advanced technology and competes in the luxury market, like Audi does, that's doubly true. In contrast to most of the cars on our roads, Audi's flagship A8 is packed to the gunwales with technology: advanced driver assists and active safety systems made possible thanks to networked steering, suspension, engine, and driveline, aided by a host of sensors and cameras around the vehicle.

Most of the tech in the car will eventually trickle down into lesser models, but until that happens, you'll need relatively deep pockets to experience the best Audi has to offer. We spent some time with a pair of Audi's latest A8s (one diesel, one gasoline) and the faster, more expensive S8 on some of Colorado's finer highways and byways recently, and we think they might be the ultimate Ars car.

Do all auto-addicts have their own gateway cars? In my case, it was the early 1990s, and it was the super sedans that did it. I wasn't wowed by the mid-engined exotic or muscle car; no, it was the technology and gadget-laden uberbarges. Cars like Mercedes-Benz's 600S or BMW's 750i were often seen competing in car magazines of the time for the title of world's best car. These were four-seaters with big engines and the ability to cruise for hours at 155 mph—in Germany, of course.

Audi entered this particular market in 1994 with the first-generation A8 (although the car only arrived in the US several years later). That car also signaled the company's intent to push the boundaries of road car technology. The A8 was all-wheel drive (AWD), in keeping with Audi's philosophy, when every other contender to the crown just drove the rear wheels.

In order not to be handicapped by the added weight of the extra mechanical bits, the chassis of the A8 was built from aluminum, saving several hundred pounds over an equivalently stiff steel version (a front-wheel drive V6 model was also available in some markets). A sportier version with a more powerful engine, the S8, debuted in 1996 and went on to star alongside Robert De Niro in the John Frankenheimer film Ronin.

Audi

Audi

Audi

Audi

The second-generation A8 arrived in the US in 2003, larger but less elegant than its predecessor. This A8 would showcase Audi's LED daylight running lights for the first time, as well as MMI, their integrated infotainment system. Gasoline engines with direct injection became available in the second-generation A8, as did a long wheelbase version with VW's W12 engine for those occasions when turning up with a mere eight cylinders simply wouldn't do. The second-generation S8 even ditched V8 power, trading it instead for a 5.2L V10, derived from Lamborghini (who was now owned by Audi).

Engineering

The current A8 arrived on our roads in 2010 on an all-new chassis, still made from aluminum in the interest of weight-saving. That's the forebear to the new models of the A8 and S8 that we spent time with. Although a 3.0L V6 gasoline engine is available (so is a 6.0L W12 if your tastes run more to potentate than plutocrat), we only spent time with the 3.0L V6 TDI (turbocharged direct Injection diesel) and the 4.0L V8 TFSI (turbocharged direct injection gasoline) cars. Both had some engine work done to go with that new power bulge in the hood; the diesel has roughly five percent more torque, the V8 about five percent more horsepower than last year's models. In both cases, that power goes to all four wheels via an eight-speed automatic transmission, split 40:60 front-to-rear under normal circumstances.

That lightweight ASF, or aluminum space frame chassis, has also been tweaked. The normal wheelbase ASF weighs just 509 lbs, and the extra five inches of the longer wheelbase version only add another 22 lbs (A8s come in two sizes—the regular A8 and a longer wheelbase A8L with more room in the back). Audi's engineers in Neckarsulm, Germany, paid extra attention to what's known as NVH—noise, vibration, and harshness—to make the A8 a more tranquil place. Mass dampers have been added to the front suspension to take out road noise and vibrations, and there's now enhanced sound insulation throughout. The TDI seems silent underway, whereas you can tell there's a V8 under the hood of the 4.0L TFSI (though only just, and only if you're up near the redline).

Audi

Audi

Audi

Both diesel and gasoline A8s are as kind to the environment as any technosedan can be when it's more than 17 feet long and weighs 4,600 pounds. The TDI sips its diesel so slowly that even with my lead right foot, it still returned 38 mpg (my co-driver for the day got an even better 48 mpg). A full tank is good for at least 800 miles, Audi tells us. The V8 can't match the diesel for fuel economy, but it makes a good attempt thanks to cylinder on demand technology. Even though the V8 is good for 435 hp and 444 lb ft, the 4.0L A8L is best in class when it comes to highway efficiency (22 mpg). Audi's valveless system closes off half the cylinders when cruising, temporarily turning the car into a V4. Active motor mounts and noise cancellation work to remove non-V8 sounds from reaching your ears (measured in the cockpit and noise cancellation done in the cockpit, not externally).



Audi

The variable-ratio steering is electromechanical. In combination with the A8's adaptive air suspension and Tiptronic transmission, that means the A8's character is almost as configurable as the excellent front seats (more on those later). You dial up different flavors of A8 depending on the occasion. Driving your Mother-in-Law somewhere? Shift the settings to Comfort and glide along in serene isolation from the world outside. In more of a hurry? Has the road suddenly grown curves? Switch everything to Dynamic and feel the steering weight and feedback increase, giving you plenty of confidence in the front end. The suspension firms up, resisting roll, and drops 0.4 inches. Above 75 mph it drops another 0.4 inches, further improving stability.

The eight-speed transmission reminds me just how far automatic gearboxes have come. It's as integrated into the car's MMI system as the steering, engine, and suspension. It pulls navigation data as well as sensors around the car to pick the optimum gear at all times. If you're less interested in fuel mileage, there's a sport mode that holds on to gears closer to the redline. Nudging the gear lever back toggles the transmission between D and S, and you can manually select gears with the paddle shifters mounted behind the steering wheel's spokes, although the gearbox will shift up to the next gear if you reach the redline.

The S8's engine is turbocharged like it's slightly more sedate siblings. It too has a 4.0L V8 TFSI engine, but this one revs a little higher and goes a little harder. It makes 520 hp—20 percent more than the A8—and a useful 480 lb ft. Fuel economy is only slightly down compared to the 4.0L A8, despite more power and a 177 lb weight increase, in part thanks to the same cylinder on demand technology (which debuted on the S8). The RS7 donates its sports exhaust, which gives the S8 more aural character, but it's never obnoxious. The dynamic variable ratio steering has a new algorithm, and the adaptive air suspension's sport mode lowers the car an extra 0.4 inches over the regular A8.

The S8 also features Audi's sport differential in order to deploy that extra power more effectively. Available across Audi's S cars, it's a limited slip differential capable of vectoring torque to whichever of the rear wheels can best use it (usually the outside rear wheel in a turn). It works by adding a pair of auxiliary transmissions to either side of the diff. These transmissions use overdrive gears that, when in use, reduce the amount of torque going to that wheel. When cornering, the S8 tells the clutch on the inside wheel to engage, sending more drive to the opposite wheel (other manufacturers achieve a similar system by braking the inside rear wheel under such circumstances). Finally, bigger front brakes and 21" (as opposed to 20") wheels all around complete the picture.

