This is it. The fastest, most powerful Cadillac ever built. The fastest, most powerful American sedan in history, for that matter. Locked, loaded, and gunning for Europe's heavy-hitting sport sedans-BMW M5, Mercedes-Benz E63 AMG, Audi RS6. Read all that again. Now pinch yourself. No, you're not dreaming. Motown-well, GM at least-has its mojo back. Meet Cadillac's monster new CTS-V. Cadzilla, if you will.Here are the raw numbers: 550 horsepower at 6200 rpm. 550 pound-feet of torque at 4000 rpm. They're only official "estimates," but as the engine under the new CTS-V's power-domed hood is fundamentally the same as the supercharged V-8 that's credited with 620-plus horsepower and at least 600 pound-feet in the hot new Corvette ZR1, you can safely assume the real SAE-certified figures will be close. "I'm confident we'll disappoint nobody with the numbers," says Ed Piatek, the CTS-V's program engineering manager.

There are no performance figures yet, but by way of context, AMG's E63 Benz nails 60 mph in 4.3 seconds. The new CTS-V weighs about the same and has at least 43 more horses and 85 pound-feet more torque. Draw your own conclusions: The car also has been extensively tested on the legendary Nrburgring Nordschliefe, and while insiders are tight-lipped on the actual lap time-for now-they will admit Cadzilla has terrorized factory hotshoes from Munich out on the daunting 13-mile road course. "People who've never been passed by a Cadillac have now had that experience," smiles Piatek.Piatek works for the GM in-house hot-shop, High Performance Vehicle Operations, headed by John Heinricy, and was the man tasked with overseeing the transformation of the COTY-winning CTS into Cadzilla. He had good raw material to work with: Unlike the previous model, the new CTS was engineered from the outset with the high-performance V-series model in mind, with extra stiffening and strengthening built in. "That was a lesson we learned with the first CTS-V," says Piatek. "If you start with this [idea] going in, there may be a small mass penalty on the base car, but there's less cost and tooling needed to do the V."

As a result, the basic CTS body structure is little altered. Most of the changes that have been made-mainly around the front and rear suspension cradles and the suspension links-are purely to handle the much higher cornering loads induced by the specially developed 19-inch Michelin Pilot Sport 2 tires and the prodigious torque output from the engine. On that last point, everything rear of the front transmission flange has been beefed up. There's a larger-diameter prop shaft, and asymmetric halfshafts (one side is a 55mm-diameter unit, the other 35mm) to help reduce wheelhop under full power launches).

It's needed, because the supercharged 6.2-liter LSA under the hood is the stoutest production engine offered in a Cadillac in the company's 106-year history. In simple terms, the CTS-V powerplant is a detuned version of the Corvette ZR1 V-8. The Eaton R1900 blower nestled in the valley pumps less air than the R2300 unit of the ZR1, for a start.

The lower combustion-chamber pressures mean the Cadillac version of the engine can get by with less-expensive components, such as cast-aluminum pistons, regular powdered-metal forged connecting rods, and 11mm cylinder-head bolts instead of the forged pistons, titanium rods, and 12mm bolts used in the ZR1 version, for example. The CTS-V also gets by with regular wet-sump lubrication in place of the ZR1's race-face dry-sump system.

The engine drives the rear wheels through the proven Tremec TR6060 six-speed manual or GM's new 6L90 six-speed automatic, the fourth-and highest torque-rated-iteration of the latest Hydramatic series. The final-drive ratio of the automatic cars has been tweaked to ensure comparable performance to the manual versions, and the paddle-shift manual mode allows drivers to hold gears until the engine is bouncing off the rev limiter.Ensuring as much of the engine's power and torque as possible was transformed into forward motion was one of Cadzilla's major engineering challenges, says Piatek. (The other? Getting rid of the enormous heat generated under the hood-the CTS-V has twice as much airflow capacity through the front of the car as the standard CTS.) To help, GM's software boffins developed an optional advanced traction-control system called Performance Traction Management (PTM).

The regular CTS has four modes of stability/traction control: everything on; traction off/StabiliTrak on; competition (which allows a measure of side slip); and everything off (although StabiliTrak will still intervene if it senses things are really getting out of hand). In CTS-Vs with the Performance Pack option (which also gets you a suedelike finish on the steering wheel and shifter and metal-faced pedals), the competition mode is replaced by PTM, which will allow the driver to select up to six different traction thresholds. The system also will act as a form of launch control on manual models.

Cadzilla will further come equipped with the latest generation of GM's Magnetic Ride Control shocks. These shocks use a magnetically reactive fluid (it has tiny iron particles suspended in it) that effectively changes viscosity at incredible speed, resulting in virtually instantaneous changes in damping resistance. Cadillac offers two damper settings-Tour and Sport, which seems pointless given the shocks' ability to adjust to wheel inputs within milliseconds. But, says Piatek, this was a late change suggested by John Heinricy, who felt a slightly stiffer static setting would sharpen turn-in response on sweeping corners. "It's like having a stiffer stabilizer bar on the car," Piatek says.