New details on Mercedes' Porsche 911 fighter

Mercedes-Benz's AMG performance-car division is forging ahead with development of its new twin-turbocharged 4.0-liter V8 powered sports car, nine months before it is scheduled to be revealed at the 2014 German Grand Prix.

Known to insiders by its code name, “C190” the two-seat coupe has been conceived to follow in the wheel tracks of the four-year-old SLS at the head of the German carmaker's lineup, aiming to challenge the heady performance and everyday driving appeal of the latest Porsche 911 Turbo at a price that insiders suggest will be in the region of $160,000 when North American sales begin in early 2015.

Originally, AMG's new front-engined sports car was tipped to revive the iconic SLC name first used by the SL coupe back in 1971. It's now planned to be called the GT, according to highly placed Mercedes-Benz sources who confirm it will be assembled on the same production line used for the soon-to-be-discontinued SLS at AMG's headquarters in Affalterbach, Germany.

The basis for the Mercedes-Benz GT AMG is a predominantly aluminum spaceframe, elements of which are shared with the structure used by the SLS. It is tied to a largely aluminum chassis that uses a suspension setup that also has close ties to the SLS. The 911 Turbo rival receives variable damping along with a raft of electronic driver aids, including the latest in radar-distance control. The body uses a combination of aluminum and composite panels, with 19-inch wheels shod with 265/35 front and 295/30 tires set to come as standard.

The GT follows the lead of the SLS in boasting a distinctive cab back profile with a long-probing bonnet and short rear-deck proportions dictated by the original SL. But in a bid to improve usability and appeal to a broader group of prospective customers, the new Mercedes-Benz adopts conventional front-hinged doors in place of the gullwing devices of its predecessor.

Another key change in design is the adoption of a liftback-style rear hatch, allowing easier access to the luggage compartment than a conventional trunk. As with the SLS, an electronically controlled spoiler will deploy from the rear of the trunk lid to provide added downforce at speeds beyond 75 mph.

Preliminary figures put overall length at 177.2 inches. This suggests the new GT will be over 5 inches shorter than the SLS. Width and height are close to the modern day gullwing at 76.3 inches and 50.7 inches, respectively. Although rumors suggest the initial coupe model could be joined by a roadster, this has been denied by Mercedes-Benz officials.

The GT eschews both the naturally aspirated 6.2-liter V8 engine found in the SLS and twin-turbocharged 5.5-liter V8 mill that powers other more recent AMG models to become the first Mercedes-Benz model to receive a new twin-turbocharged 4.0-liter V8.

The modular unit, also set to appear in a successor to the C63 AMG in 2014, shares its architecture with the turbocharged 2.0-liter inline four-cylinder engine used in the recently introduced A45 and CLA45. Endowed with a 90-degree cylinder bank angle, it will be mounted low and well back in the engine bay almost entirely behind the front axle line for the best possible weight distribution.

Official figures have yet to be revealed, but AMG officials said the new engine has been tuned to deliver a specific output of over 120-bhp per liter to give it a claimed 493 hp.

Despite giving away over two liters in displacement to the SLS, the inclusion of forced induction in the form of turbocharging also sees the GT's torque reserves swell to a similar level to the car it will replace on AMG's production lines during the third quarter of 2014 at 480 lb ft. But while the SLS's peak torque arrives at a relatively high 4750 rpm, the GT's is said to be delivered below 2000 rpm for added low-end performance and greater flexibility over the entire rev range.

The power is channeled rearward via a lightweight carbon fiber prop shaft to a seven-speed dual clutch gearbox mounted within the rear-axle assembly. A mechanical-locking differential is then used to apportion drive to each of the rear wheels.

The gearbox is described as a development of the Getrag-produced unit used in the SLS. It has been upgraded to include an automatic stop/start function for added fuel savings in city driving. Brake energy recuperation is also used to boost driveline efficiency. New software mapping claims to improve shift quality.

With a predominantly aluminum structure and other lightweight construction measures helping to suppress curb weight to around 3,417 pounds–154 pounds less than the SLS–the GT claims to possess a weight-to-power ratio under 7 pounds per hp.

Straight-line performance is yet to be officially certified, but Mercedes-Benz sources hint at a 0-62 mph time “well under 4.0 seconds” and top speed “above 190 mph.” At the same time, they claim the GT will return combined cycle consumption “close to 30 mpg.”

AMG's new boss, Tobias Moers, is going all out to provide the C190 with class-leading handling. In a move that has infuriated rival Porsche, Mercedes-Benz's performance car division recently secured the services of Markus Hofbauer, who is credited with much of the chassis development carried out on the latest 911. He has been charged with the task of fine-tuning the handling of the GT, which is already said to lap the N

By Greg Kable