DETROIT – General Motors Corp. delivers the first surprise of the North American International Auto Show with a Cadillac CTS concept coupe, a vehicle that exemplifies the luxury brand’s future design direction and confirms a new diesel-engine application.

“It’s a little too early to announce production, but if you look underneath, you can see that it’s a real car,” says GM Vice Chairman and product boss Bob Lutz. “We call it a concept coupe, but it would be reasonable to assume that we plan to expand the Cadillac line to include a (car) like that.”

The long-rumored coupe caught the motoring press by surprise, as it was the one introduction GM did not brief journalists about ahead of the show. Ed Welburn, vice president, GM Design, says it came as a bit of a surprise to him, as well.

“To be honest, this vehicle was not supposed to exist,” he says. “As designers were completing the CTS sedan, the team continued to bring forward creative ideas and said what about a coupe.

“It quickly developed from a mock sketch to a clay model. It was so beautiful, we had to pursue its design and the end result just sings.”

Clay Dean, global director of design for Cadillac, says the coupe hits a sweet spot for the brand.

“Obviously, it’s a concept today, but as a luxury manufacturer, we need a vehicle in every segment, and we really need an expressive vehicle,” he tells Ward’s. “This coupe is just that. It is the next great design from Cadillac.”

“It really allows the personality of the CTS sedan to come out – take off a couple doors, lower the roof, and it becomes a pallet to express the forms and gestures of the Cadillac brand.”

For example, the 2 + 2 concept recalls the great tailfins popularized by Cadillac coupes of the 1950s through a subtle execution atop the taillamps. Light-emitting-diode light pipes add a more contemporary look to the vertical lamps, while a strong centerline crease provides drama to the rear and also nods to the brand’s design heritage.

Although the CTS coupe matches the length of its production sibling, it sits 4 ins. (10 cm) lower, with wheels pushed to the corners for a sleek, “crouching-cat” look.

“It’s as if a wet canvass were stretched across the wheels,” Dean offers, noting the bulging rear fenders were sculpted by hand in the design studio.

The coupe receives oversized, 20-in. chrome, 7-spoke wheels up front and a 21-in. set in the rear. High-performance brakes in bright yellow provide stopping power.

“The whole exterior design – with its simple lines – appears as if it were performed with a single pen stroke,” Dean says. “For today, this becomes the ultimate expression of Cadillac design.”

Black Recaro seats with yellow ochre-colored inserts rank among interior highlights that additionally include yellow stitching for the instrument panel and shift knob; carbon-fiber accents for the console; and ambient lighting that provides a distinctive look after dark.

Technology also takes prominent place, most notably with a Bose audio system, 40-gigabyte hard drive and navigation screen that rises from the center of the IP.

While a production coupe likely would receive the 304-hp, 6-cyl. engine from the current sedan, GM says the concept also can accommodate a new 2.9L turbodiesel the auto maker is developing for international markets. A 6-speed manual transmission provides power to the rear axle.

The diesel, earmarked exclusively for the CTS, will deliver an estimated 250 hp and 406 lb.-ft. (550 Nm) of torque. But only in international markets, Lutz says. “Not for the U.S. Not yet. It’s obviously feasible. It just requires way, way, way too much emissions work.”