New Bentley Continental GT: Stunning Performance Engine Details Confirmed | Part Two

But this is just the start of this engine's story: it has many other distinctions to its name. Its exterior dimensions, for instance, make it the smallest 12-cylinder engine currently in production, despite its considerable 6-litre displacement. The engine is just 653mm long, 820mm high and 714mm wide. This has been made possible by its 'W' formation where instead of arranging the cylinders in two long rows as you would in a conventional V12 configuration, each bank of cylinders is actually staggered, effectively creating two V6 engines mated on a common crankshaft. The angle between the two main banks is 72deg, that between the staggered cylinders just 15deg. The result of this is an exceptionally compact motor, a trait that brings advantages in many areas. Clearly it helps with weight distribution as a small engine is easier to locate nearer the centre of the car. This in turn helps the overall packaging of the car and, in particular, its frontal crash performance, a crucial consideration in a Bentley which has a short front overhang as one of the main features of its design language.

It is no secret that the basic engine architecture has been supplied to Bentley from its parent company, the Volkswagen Group, but by the time Bentley's powertrain team had finished re-engineering it to an exclusive specification for the Continental GT, it can now be considered a unique engine in its own right.

Clearly the major engineering challenge was to adapt the engine to accept twin turbochargers, a process that required major re-engineering of the block, the replacement of many internal components and all new inlet and exhaust systems.

The engine features special pistons, specifically designed for the Continental GT in order to deliver the desired compression ratio of 09:01. The engine also features seven main bearings, pent-roof combustion chambers and variable valve timing on both inlet and exhaust valves. The timing is infinitely variable within its fixed range which is some 52 degrees on the inlet camshafts and 22 degrees on the exhaust camshafts.

A huge amount of work was also undertaken to ensure the Continental GT could use air to air intercoolers rather than the water to air variety. Fitting them within the already cosy confines under the Continental GT's bonnet was not the matter of the moment, but Bentley's engineers regarded their inclusion in the specification as not negotiable and, after several months work, they were duly integrated into the under bonnet package.

The Continental GT also uses a dedicated exhaust system, using two six-into-one manifolds. Much attention has been paid not only to ensure the exhaust provides maximum efficiency, but also that its sound is appropriate to the fastest Bentley road car in both tone and volume.

The twin turbochargers operate at only the comparatively conservative boost pressure of 0.7bar to equip the Continental GT with its headline performance. Given this, the existence of maximum torque at 1600rpm and the engine's 6-litre capacity and it's easy to see how turbo-lag, the sole undesirable side-effect of this variety of forced induction, has been effectively removed from the equation. As with all Bentley-designed powerplants since the birth of the company in 1919, smooth power is not something you need to wait or ask for - it is there, at your disposal at every point of the rev-range from idle to its 6300rpm red-line.

Controlling all this power is Bosch's state of the art ME 7.1.1 engine management system which comes complete with two throttle bodies, exhaust gas temperature regulation, boost pressure regulation, two air mass sensors, four knock sensors with adaptive learning and the latest ESP 5.7 electronic stability programme. Ignition is achieved without the need for a distributor, thanks to each cylinder being provided with its own coil. The engine is fully compliant with future Euro IV emissions regulations and has been calibrated to run on standard 95RON octane pump fuel.

Such is the power of the Bentley Continental GT's powertrain that Bentley engineers took the decision to reinforce its engine mounts with kevlar bindings to make sure it does not move even under the most extreme circumstances.

continues... | Part Three
Published 6 March 2003 Melanie Carter
 

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