all-new RS 5 Coupe uses the same Porsche-engineered biturbo V6 as the Porsche Panamera, and uses it to such effect that it extracts 444 horsepower and 443 pound feet of torque from its 2.9 liters of displacement. Those 443 lb-ft is a full 125 more than the V8 could ever muster, and it's available from 1,900 rpm to 5,000 rpm. That kind of power is sufficient to push the RS 5 to 62 miles per hour in 3.9 seconds on the way to a limited 155-mph top speed (there's an optional 174-mph limiter, too).

The all-wheel-drive Quattro RS 5 Coupe doesn't suffer much in performance in the switch from the naturally aspirated 4.2-liter V8 to the force feeding of a V6, but it remains to be proven whether the sound can be as captivating.

The Porsche-sourced engine continues the current trend of "hot vee" engines, situating both of its turbochargers inside the vee-angle of the engine, and combines centrally-mounted direct fuel injectors with a short stroke to boost power and improve economy. The high-compression Miller-cycle motor also lets the RS 5 Coupe pull its consumption down 17 percent to 32 miles per gallon (or 197 grams/km of CO2 emissions) on the European driving cycle. Expect US mileage numbers to be significantly lower.

The new RS 5 is also significantly lighter, pulling 132 pounds from the previous V8-powered model's mass, despite all the turbo plumbing, to weigh 3,649 pounds. A BMW M4-style carbon-fiber roof helps keep the weight down.

Audi feeds its newfound V6 power through an eight-speed automatic transmission and permanent all-wheel drive, with 60 percent of the drive nominally headed to the rear end. The hard-turning sport differential is an option.

Audi's reborn RS 5 rides on five-link suspension systems at both ends to keep suspension bits precisely location and improve ride quality, while sitting 0.8 inches lower than the standard A5 Coupe. It has the usual Audi Sport array of go-faster options for its go-fastest front-engined coupe, including the more aggressive Dynamic Ride Control damping system, carbon-ceramic brakes and sharper steering ratios.

"The new Audi RS 5 Coupé is the gran turismo among the RS models," Audi Sport GmbH CEO Stephan Winkelmann said. "The high-performance Coupé combines elegant aesthetics with high everyday usability. The car's V6 biturbo has been developed from the ground up and provides significantly more performance coupled with higher efficiency," he said.

Winkelmann claims Audi's designers drew their inspiration from the wild and wicked 90 quattro IMSA GTO racers that dominated US racing circuits in the post-Group B era. At 186 inches, it's 3 inches longer than the outgoing RS 5, with its bulging wheel arches pushed out more than half an inch compared to the standard S5 Coupe's bodyshell. It has a wider, flatter single-frame grille than the standard models, along with enormous air intakes for radiator and brake-system cooling. There are also tinted bezels for the LED (and optional Matrix LED) headlights, while the car rides on 19- or 20-inch forged alloy rims and punches its emissions out of unique oval tailpipes.

Inside, the RS 5 Coupe continues the Audi Sport (nee Quattro GmbH) love affair with black and diamond stitching. It introduces new bits to the A5/S5 Coupe's cabin, including an upgrade to the Virtual Cockpit digital instrument cluster to include feedback on torque, g-forces and tire pressures. It also boasts a dash-mounted shift light, which seems redundant given that it slushes through an automatic transmission. The interior delivers permanent internet connectivity via LTE and a wifi hotspot option, and links smartphones via CarPlay and Android Auto.