In a novel approach, Mercedes has provided the F700 with three conventional front-hinged doors and a fourth rear-hinged door at the rear on the right. That's designed to ease entry and exit for those seated in the right rear seat, which can be set either in the direction of travel or turned through 180 degrees.
At 5180mm long, 1960mm wide and 1438mm high, the F700 is a scant 25mm shorter but a considerable 90mm wider and 37mm lower than today's long-wheelbase S-class, and on a 285mm longer wheelbase, at 3450mm.
Frugal and fast
More than its radically styled exterior, it is the F700's compact variable-compression twin-turbocharged 1.8-litre four-cylinder DiesOtto petrol engine that Mercedes promises will have the biggest bearing on its future model range.
Claimed to offer the power, smoothness and low emissions of a typical petrol engine in combination with the torque, flexibility and frugal properties of a diesel, the new unit is capable of switching between two distinctively different ignition processes depending on the driving conditions.
When started, the aluminium block engine runs in so-called petrol mode, with an air/fuel mixture being injected into the cylinders and ignited by a spark plug. But once temperatures have risen sufficiently and the engine is under light loads it automatically switches to diesel mode, where the compression ratio is raised and the spark plug is deactivated in a move aimed at enhancing overall efficiency.
Despite its relatively meager capacity by luxury car standards, the F700's advanced engine punches well above its weight with an output that compares more than favourably with Mercedes' existing four-valve-per-cylinder 3.5-litre V6 petrol and 3.0-litre V6 common rail diesel units at a claimed 238bhp.
With an electric motor designed to provide an additional burst of output under acceleration, the new research vehicle's peak power tops out at competitive 258bhp in hybrid mode. Torque, meanwhile, is rated at a prodigious by four-cylinder petrol engine standards 295lb ft. It's enough, says Mercedes, to provide the F700 with a 0-62mph time of 7.5sec and a top speed limited to 125mph.
Even more impressive are its environmental credentials. With combined cycle fuel consumption of 53mpg, the slippery new F700 betters today's S350 by almost 18mpg. It's impressively clean, too: CO2 output is just 127g/km. Mercedes says the new engine already adheres to the tough new EU6 emission standard due to come into force in 2012.
Another feature Mercedes is touting for possible inclusion on future production models is a highly sophisticated Pre-Scan suspension system. This reads the road via two headlamp-mounted sensors, which constantly send out infra-red beams to detect unevenness in the bitumen or changing road conditions, allowing the suspension and associated driving aids to react before you've even hit an imperfection or wet section of black-top.