2007 Audi RS 4

Audi's captive tuner, quattro GmbH, stopped building the blistering 450-horse twin-turbo RS 6 at the end of 2003. We miss that supersled. Happily, its spiritual successor, the RS 4, arrives next spring. Its engine packs "just" 414 naturally aspirated horses, but thanks to nimble A4 bodywork, each horse is burdened with the same nine-pound load as the ponies in the RS 6.

The quattro team fortified the 4.2-liter V-8 from the inside out, starting with a new crankshaft, bearings, rods, and pistons capable of spinning past 8000 rpm. Power is basically torque times rpm, so revs buy horses. So does direct fuel injection by enabling higher compression (12.5:1 versus the S4's 11.0:1). Displacement and boost buy torque, but the RS 4 gets neither, so while power jumps by 74 horses, torque is up just 15 pound-feet over the S4--to 317, 98 pound-feet shy of the RS 6.

This thrust flows through a new Torsen center differential that biases the torque 40/60 front/rear en route to four wide 255/35R19 tires. Eight-piston, four-pad front calipers clamp enormous 14.4-inch vented and cross-drilled rotors. The bodywork is slammed 1.2 inches and stretched to accommodate the giant rolling stock.

The rest of the exterior is zooted up commensurately, leaving only the roof and doors in common with an A4/S4. Interior upgrades include comfortably supportive seats and carbon-fiber trim that looks as deep as a Magic Eye poster.

Twist the key, and the high-strung eight settles into a lumpy, hot-cam idle. Blip the throttle, and the pops and mini-backfires on overrun confirm this is one extreme machine. It's difficult to drive smoothly in low-adrenaline, mother-in-law mode--especially with the "S" button depressed (to uncork the exhaust and quicken throttle response). The Germans say S stands for "spaB," which means "fun" and sounds like "spaz." Anglophone passengers may mutter that term in reference to your footwork, as the clutch engages and releases abruptly.