Driving Impressions

By July 19, 2004

In the 2005 Audi A8, a driver can use the Driver Information Display to set the optional Adaptive Cruise Control, which minds tailgating and maintains a safe, pre-determined distance to the car ahead. The Electronic Stabilization Program can help control the car when the driver can't. Electronic Brake-force Distribution keeps the car balanced in a panic stop, and Brake Assist slams the binders harder if the driver doesn't press as hard he or she should. Adaptive Air Suspension keeps the ride smooth and tires planted no matter the surface. There are moisture-sensing wipers, high-intensity headlamps and ten airbags. Yet all these advanced systems, identified by a confusing array of acronyms, don't mask one crucial point. The A8 can be a complete joy to drive, reminding all but the sensory deprived how pleasant gobbling miles in a big, fast luxury sedan can be.

The first impression at the wheel of an A8 is its smoothness. There's nothing remotely resembling a squeak or rattle, and almost no vibration in the cabin.

The A8 can be a thrill to drive. The 4.2-liter V8 delivers powerful acceleration, but its power delivery is sophisticated, not crude. The engine was revised for 2004, and it delivers more power than its predecessor. Both the short- and long- wheelbase A8 4.2s can sprint from 0 to 60 mph in just 6.3 seconds, according to Audi, impressive given their size and weight. Top speed is electronically governed at 130 mph. The V8 responds with a muted roar to every poke at the gas pedal. No matter how fast the A8 4.2 is already going, the driver can tap into a deep well of acceleration-producing torque.

And if that isn't enough, you can raise the ante with a 6.0-liter 12-cylinder engine. New for 2005, the A8 L 6.0 gets Audi's unusual W12, which is actually two single-cylinder-head VR6 engines, splayed like two Vs and mated at the crankshaft. Each bank has its own computer controls and throttle.

Other things equal, is this W design more powerful or economical that a conventional V12? Not really. Torque and horsepower are comparable to the 6.0-liter V12 in BMW's 760Li. The 6.0-liter V12 in the Mercedes S600, with its twin turbochargers, is substantially more powerful than either the Audi or BMW engines.

The advantage of the W12 lies in the packaging. Despite its extra cylinders, it is no bigger than the typical V8 with less displacement. Indeed, Audi's W12 is actually a bit smaller by overall dimensions than the smaller-displacement V8 in the A8 4.2. The W12 therefore allows Audi to build a 12-cylinder sedan with all-wheel drive. With a conventional V12, there would simply be no space in the engine bay for a differential and other components required to power the front wheels, according to Audi.

Regardless of the packaging advantages, the A8 L 6.0 is a blast to gas. Throttle response is immediate, and it delivers acceleration-producing torque in a wide, flexible band befitting a luxury carmaker's flagship sedan. The W12 pulls hard up to its 6200-rpm redline, and it feels like there's still more power coming when it hits the rev limiter. Moreover, the revs translate to executive-class thrust. Audi reports 0-60 mph times of 5.0 seconds, with top speed governed at 155.

With either engine, the A8's six-speed automatic shifts up or down according to the driver's wishes, deftly sensing how quickly and how hard the throttle is mashed. Upshifts are silky smooth in full automatic mode; in some instances, downshifts could come quicker, but the reserve of torque in either engine more than compensates for any shift lag. This transmission is an improvement in every respect over the A8's previous five-speed automatic. It helps the A8 achieve better fuel economy with the improved acceleration, and V8-powered variants are no longer saddled with a federal Gas Guzzler Tax.

The automatic also features Porsche's Tiptronic system, allowing the driver to slide it into a manu