Not so fast on Mercedes-AMG C63 R

MERCEDES-AMG insiders have hosed down speculation that the wicked 450kW bi-turbo V8 destined for the E63 S will be shoehorned in the C-Class to create an R-rated C63, saying the “plumbing” needed for such a high-output engine just won’t fit.

The same applies to the Mercedes-AMG GT, which means that the 430kW version of the AMG V8 in the race-bred GT R Coupe might be as high as it goes, at least in the current generation.

Mercedes-AMG V8 engine program manager Bertram Tschamon told GoAuto at this week’s GT Roadster launch in Phoenix, Arizona, that extra under-bonnet space of the E-Class permitted the bigger intercoolers, larger turbos and other necessities required to lift the V8 to 450kW.

He said that in the case of the GT and C-Class, those larger items could not fit, so no such move was planned.

“The reason we put the twin-turbochargers in the vee of the engine was for space reasons – to make the engine fit,” he said.

“But to get another 50 horsepower, we would need bigger turbos, and then we need bigger intercoolers, more cooling and bigger exhaust pipes. That is possible in the E-Class.”

Mr Tschamon said engineering modelling for high-performance engines was a step-by-step process that took into account cooling requirements, not just for the engine water, but also oil and the turbo intercoolers.

He said the higher output the engine, the bigger these items had to be to cope.

Mercedes-Benz Australia/Pacific public relations, product and corporate communications manager David McCarthy said he was not aware of any Mercedes-AMG project to create a C63 R as described in the United States report.

“I wish,” he said. “Look, we would of course take such a car if it became available, but I am not aware of it.”

The current most powerful C-Class is the C63 S in sedan, coupe and cabrio forms, belting out 375kW and 700Nm – sufficient for a 4.0-second dash from zero to 100km/h.

By contrast, the AMG’s upcoming E63 S 4Matic with its 450KW and 850Nm can zip to 100km/h in 3.4 seconds.

In the C-Class, one of the problems of generating more power from the AMG V8 variants is lack of under-floor space for bigger exhaust pipes.

Mr McCarthy said the CLK63 ran into similar hurdles in 2006, limiting the power output by about 20kW compared with the CLS63.

The two-door, two-seat GT is believed to have the largest intercoolers that will comfortably fit in front of the engine for the high-output 410kW GT C and 430kW GT R.

Also, the twin turbos sitting on top of the engine just clear the bonnet by a matter of millimetres, precluding bigger units without a major redesign.

“I am not sure anyone needs more than 430kW, to be honest,” Mr McCarthy said.

Mr McCarthy also hosed down speculation that a C63 R would be based on the sedan with items such as the rear seats ripped out and a switch a carbon-fibre bonnet to reduce weight.

“Why would they take the back seats out of a sedan?” he said. “Maybe a coupe would make sense.

“And OK, carbon-fibre would save weight, but as the bonnet is aluminium already, it would not save much.”