Bentley re-engineers its flagship

  • 13-Oct-2009 09:16 EDT

Bentley's new Mulsanne has a new version of the company's long-established 6.75-L engine.

Cylinder de-activation, weight saving, reduced fuel consumption and emissions, a new chassis, and huge amounts of wood for its interior mark out Bentley’s new Mulsanne, revealed at the 2009 Frankfurt Motor Show.

Replacing the Arnage, production of which was completed recently, the new car is bigger, more luxurious, and more powerful. “And it has 300% more wood in its interior,” said Mulsanne Project Director, Ashley Wickham.

One of the more significant mechanical elements of the car is the use of cylinder de-activation. Other companies—including Cadillac—have flirted with the technology over the past two decades, but new systems now make it feasible.

“We use the hydraulic tappets to activate or de-activate four of the car’s eight cylinders," said Wickham. "The Mulsanne will cruise normally in four-cylinder mode on a light throttle, but when the accelerator is depressed, it smoothly transitions to V8 mode. We now have the engine management systems and control systems to make this possible." The Mulsanne also has cam-phasing.

Although the Mulsanne has the same block that Bentley has used for five decades, it has been extensively re-engineered with what Wickham described as “a considerable amount” of weight taken out of it. It has lighter pistons, conrods, and a forged crankshaft to reduce reciprocating masses and internal friction: “We have reduced thicknesses and dimensions where possible and have looked back into the design concept of the engine to see where we could achieve re-engineering.”

The engine has two low-inertia Mitsubishi turbochargers. Output figures include 377 kW (506 hp) and 1020 N·m (752 lb·ft), the latter from 1800 rpm. The Mulsanne also has ZF’s new eight-speed automatic transmission.

In aggregate, these changes and additions bring some 15% in fuel consumption and emissions reductions. The latter is said to be at less than 400 g/km, but Bentley has not issued specific figures because it believes it can make further reductions before the car goes on sale next summer.

A new chassis has also been designed for the car, which at 5575 mm (219.5 in) is 172 mm (6.8 in) longer than the Arnage, 150 mm (5.9 in) of that coming from the extended wheelbase.

The chassis has a totally new underfloor. The suspension has been re-engineered with completely new parts or those that have been identified within the Volkswagen Group. Front and rear subframes are completely new. Air suspension is now used, and wheels are 20 in standard, 21 in optional.

Active damping is used and a new Drive Dynamics Control gives four modes called Bentley, Sport, Comfort, and Custom for tuning to bespoke settings. Ceramic brakes are available.

The body includes aluminum hood and doors (inners and outers, with the former superformed). The front fenders are also of superformed aluminum to give shape to a very large and complex part. The trunk lid is of SMC (sheet molded composite) material. The gauge of the body’s steel has been optimized where added strength is needed. Weight saving achieved by these measures is 5-7%.

Styling includes two large headlamps with chrome surrounds, flanked by two smaller outboard lamp clusters. The car has 3-D "floating-effect" rear lights. Both front and rear lights are by Wipac. Extensive use is made of stainless steel trim, but door handles are chromed.

Because development continues, precise weight and performance figures have yet to be announced, but a 0-97 km/h (0-60 mph) time of about 5.5 s is expected.

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