Smoke comes from the rear tires of the 2009 Cadillac CTS-V during a burnout. The car is powered by a 6.2-liter V-8 with 556 horsepower.

GM

The accelerator is pinned on the floor and the speedometer is sweeping well into triple digits. Blurring along a straightaway that drops out of sight on a steep hill, the car proves capable and willing. I’m just not so sure I am. This racetrack is unfamiliar and my nerves are urging my foot to let off the gas as I hit 135 miles per hour.

It’s only later, in the pit lane, that something else kicks in: wonderment. Was I really doing those speeds in a Cadillac?

Yep. The venerable GM brand has shed its image as the carmaker favored by octogenarians living in Florida. Models like the XLR roadster and Escalade SUV have sexed things up with innovative designs and a decidedly non-retirement-home attitude.

The $60,000 CTS-V, which goes on sale this month, is the road-raging performance version of the excellent CTS four-door sedan. The original CTS-V, sold between 2004 and 2007, was based on the first-generation CTS. Yet the second-generation CTS blows the older version out of the water in terms of driving quality and interior. It was one of my favorite releases of 2007 -- see the review here -- so it’s no wonder I have high expectations for the CTS-V.

Here’s the funny thing about sports cars: the flashier they are, the slower you find yourself driving. Recently I spent a week with a $250,000 Lamborghini Gallardo LP560-4. It was bright orange. On a 200-mile road trip I drove under the speed limit, with minivans flashing by me. After all, who do you think the cops would have pulled over if I was flowing with the rest of traffic?

This is the hidden beauty of the CTS-V. It’s an eye-catching car, with a fierce front grill, 19-inch wheels and a bulging hood, but outwardly it’s no Lamborghini. You can drive around like an ordinary citizen 364 days of the year. On the 365th, though, when a crazed serial killer is after you in his tricked-out kidnapper van (hey, it could happen!), you have a Herculean 556-horsepower engine at your disposal.

That means 0 to 60 in 3.9 seconds and the quarter mile in 12 seconds. The killer and his machete will be lucky even to catch your tail lights.

The CTS-V can be a fiend in its own right. The Hyde-esque character comes from the supercharged 6.2-liter V-8 engine. As you creep around in traffic, few would expect it’s capable of summoning 551 pound-feet of torque.

The switch between personalities is effortlessly managed by magnetic ride control, which adjusts the suspension to the type of driving and road conditions.

Cadillac is keen to show off the CTS-V’s evil side, and a 4-mile road circuit is a good place to do it. With the stability control in competition mode, you can drift the rear-wheel-drive sedan through corners, sliding the back end out with a stab of gas. The suspension is stiff but not punishing with the shocks dialed into sport mode. The car’s top speed is unrestricted, and as I sprint down the straightaway, Cadillac’s claim of 191 mph seems pretty believable.

The only downside is the car’s considerable heft. In quick directional changes, its 4,300 pounds are hard to hide. The car is considerably heavier than the last-generation CTS-V.

I test both the six-speed manual and the six-speed automatic transmission with paddles behind the wheel. My preference is the manual, if only because I feel more in tune with the vehicle, though either would make a good choice.

On most days, buyers will enjoy the sedan’s Jekyll-like aspects. In terms of layout, comfort and ease of use, the CTS-V has one of the best interiors among luxury performance sedans. It gets only minor changes from the CTS, such as an optional steering wheel and shifter and a speedometer encircled with red lights that flash on as you near the red line.

What hasn’t changed are the seats. Big and comfortable, they’re ideal on a road trip or around town, though in spirited driving they don’t offer enough support. I find myself slipping around like there’s butter on the leather.

The answer is optional seats made by Recaro, which specializes in racing-spec seats. Finding them in a Cadillac seems odd, like an Eames chair in the living room of a Victorian house. These are pretty elegant, fully adjustable and clad in black, though they add more than $3,000 to the tag.

As for fuel-station stops, while the official EPA numbers aren’t in yet, Cadillac estimates 13 mpg city and 19 highway.

So, in these cash-strapped times, how desirable will the performance version of the CTS be? At an MSRP of $60,000, it carries a weighty premium over the direct-injected CTS’s base of $40,000. Yet it’s some $25,000 cheaper than competitors like BMW’s 500-horsepower M5 sedan.

As I roll the CTS-V onto the track for a last lap, I steel myself for taking the straightaway as fast as I can. After all, what’s the point of 556 horses if you don’t let Mr. Hyde roam free every so often?The 2009 Cadillac CTS-V

Engine: 6.2-liter V-8 with 556 horsepower and 551 pound-feet of torque.

Transmission: Six-speed manual or six-speed automatic.

Speed: 0 to 60 mph in 3.9 seconds.

Gas mileage per gallon: Estimated 13 city; 19 highway.

Price as tested: $67,000.

Best features: Comfort and overall drivability coupled with high-speed capabilities.

Worst feature: A hefty weight of 4,300 pounds.

Target buyer: The thrill-seeking driver who needs four doors and doesn’t want to spend the extra $25,000 for the BMW M5.