The New Bentley Continental GT Design Concept Launched At Paris Motor Show | Part Two

Bentley Continental GT

Bentley Continental

Design

The design brief for the Continental GT was as simple to state as it was difficult to realise: create a car with as much room as the most spacious coupés on the market, equip it with the performance and responses of the world’s most dynamic supercars and retain the whole within compact dimensions.

There are many questions raised by such a demanding specification and it took sizeable measures of blue sky thinking and detailed innovation before it could be realised.

But go looking for the real key to providing sufficient interior room and you’ll need to start your search under the bonnet. There you will discover that the secret of the Continental GT’s interior room is, in fact, its engine. By choosing the basic architecture of the W12 powerplant used elsewhere in the VW Group, Bentley’s engineers were provided not simply with the opportunity to develop it into a unique Bentley engine, but also to exploit its phenomenal packaging attributes.

Instead of using two long banks of six cylinders, as featured on all conventional V12 motors, the W12 staggers the cylinders in each bank creating effectively two extraordinarily narrow angle (15deg) V6 engines sharing a common crankshaft and giving rise to the ‘W’ formation. This naturally provides a phenomenally short engine for its considerable capacity, and frees up space that can be reapportioned to the car’s interior. Indeed it is the shortest twelve cylinder engine on the market.

Even so and allowing for extra room provided by the super-short engine, there was still some hard thinking to be done if the interior space targets were going to be met within the swooping roof line of the Continental GT. Happily, help was again at hand and this time it was provided by history.

One key to maximising interior space is raising the so-called 'H' point – the position in which the driver and front passenger hips naturally sit, and which in all Bentleys is elevated above where it would be in a conventional supercar. The benefits are many: first it means the commanding driving position - another Bentley hallmark – is retained; secondly it means the driver and passenger’s hip to heel angle is as close to anatomical perfection as is possible. Finally, and critically, a high and upright driving position liberates vital room in the back for rear seat passengers.

The result is a true two plus two, a phrase rather devalued today by being applied to cars with little more than a ledge behind the front seats. In the Continental GT it means a car capable of carrying two adults and two children in comfort for unlimited distances.

Another less obvious but no less important benefit of the Continental GT’s design is the omission of a B-pillar. There are many aesthetic reasons for adopting the pillarless look, but for those inside looking out and particularly those in the back, the unbroken expanse of glass from the front to the rear of the cabin provides a feeling of great space and airiness. In the GT coupé, the pillarless feature and other design touches such as slimmed down front headrests mean an unparalleled view from the rear seat for a car in this class.

Even the 355 litre luggage capacity has only been achieved through fresh thinking and innovation. In cars of this size, it is accepted practice to site the fuel tank between the boot and rear seat, adding to the overall length of the car, removing interior and boot capacity and, crucially, removing the possibility of loading long items through the boot into the rear cabin. The Continental GT’s fuel tank, however, is under the floor of the car. It’s a tricky piece of design for to house a 90 litre tank there requires it to straddle the transmission tunnel but there’s no doubting the effectiveness of the result. Not only is there enough boot space to swallow enough luggage for a family fortnight away, if that holiday happens to be to the ski slopes, it will take all four sets of skis inside the car or two pairs of skis and a couple of snow boards. All of this mind, without having to resort to an unsightly and insecure roof rack.

Design Technology

The Continental GT is the first Bentley to have been designed entirely in the virtual world. That is to say every single component, down to the smallest washer or bolt was not merely computer designed, but designed into the Continental GT concept alongside every other part.

Using the very latest CATIA-based Computer Aided Design (CAD) programmes, the Continental GT represents a huge step forward in Bentley design technology. With all components existing in the virtual world before a single one is created as a physical property, it is possible to see how each part interacts with all the others, illuminating problems and conflicts that, in the past, may never have come to light until the part had been machined.

This process cuts down development time and costs and, rather more importantly, it enables Bentley’s engineers to design in reliability and consistency in each component and assembly, to deliver unprecedented levels of quality in the finished car.

Indeed, one critical aspect of the design work that is now done in the virtual world enables Bentley to produce theoretically perfect component designs before the Data Control Model (DCM) is made.

The DCM is as close to a mathematically faultless physical model of the interior and exterior of the car as it is possible to have. And it is from this that are taken all the measurements used to specify the tools that will make it when production starts, so the importance of getting it right can scarcely be overstated.

Designing the car this way results not simply in a better built and more reliable product, it is also likely to be safer too. Bentley’s advanced Dynamic Crash Analysis (DCA) capability means much of the trial and error traditionally associated with providing a car with good impact resistance has been bypassed. Indeed so highly developed are the procedures that Bentley’s engineers can put a Continental GT through a real world crash test with great confidence that the result will vary in no major way from those suggested in virtual world.

Nevertheless it should be understood that DCA, as with all virtual design work will never replace real world test procedure, nor was it ever designed to. Its role is simply to ensure that by the time these tests are conducted, the product is in as good shape as possible to meet each new challenge.

Bentley Continental GT Gearbox

Powertrain

Even before it had been determined how the Continental GT would be powered, two crucial decisions were made and set in stone. First, the Continental GT would possess a new level of performance – one that placed it among the very fastest cars on earth; secondly the provision of that performance would remain inimitably Bentley. Reconciling these issues would require a great deal of power, but more importantly, huge torque delivered evenly across the rev-range.

The W12 formation engine was a natural choice for Bentley. Not only did it have the potential to deliver these objectives, it also boasted the incredibly compact dimensions required to realise the Continental GT’s packaging requirements.

Importantly the basis of such an engine already existed within the VW Group. While Bentley would still need to design its own application of it (not to mention the facility in which it would be assembled), the advantages of taking a known quantity, if only as a starting point, are clear to see.

Once this decision had been made, it was necessary to change entirely the specification of the engine to adapt it for the very particular purpose needed by the Continental GT. First of all it was clear that the power output of the standard engine – while impressive for a normally aspirated engine – was not going to generate the kind of power and torque figures required to make it not only a great engine but, more importantly, a great Bentley engine.

It was both impractical and undesirable to increase the engine’s capacity beyond its existing 6-litre displacement so Bentley’s engineers decided that it should be turbocharged. Forced induction was first used on standard Bentley road cars as long ago as 1928 with the introduction of the famed ‘Blower’ Bentleys, while turbocharging has been a hallmark of Bentley engine design for 20 years. So, in line with modern practice and consistent with the Bentley Arnage Series Two introduced earlier this year, the use of twin turbochargers was selected as the preferred means of delivering a dramatic hike in both power and torque.

Using two turbochargers on an engine with two banks of cylinders has many advantages over the old, single turbo method. For a start, because there are two of them, each turbo is much smaller than would be a single unit designed for the same purpose. This means they have less inertia and therefore accelerate up to and back down from operating speed much more quickly, minimising turbo-lag. Two turbochargers also means the car’s catalytic converters can be sited next to the exhaust manifold where they heat up extremely quickly, offering greatly reduced exhaust emissions, particularly when the engine is cold.

For this application KKK turbochargers were chosen and carefully integrated into the under-bonnet package.

At the same time, Bentley’s engineering team modified the internal componentry of the powerplant until all its power, torque, emissions, consumption and durability targets had been met or exceeded. Further details of these changes will be released nearer the time when the car goes on sale in the second half of next year.

For now, however, it can be confirmed that Bentley will make good its promise to power the Continental GT with an engine of ‘more than 500bhp’. But power is nothing without the torque to back it up. The idea that a Bentley should be fabulously responsive from very little more than idling revs is not new – indeed it was a precedent set by WO Bentley’s first six cylinder cars over 75 years ago – but the Continental GT will take the execution of the concept to new heights, providing relentless acceleration from 2000rpm to its red-line.

Having created one of the world’s most powerful and responsive engines, it was clear that an equally extraordinary transmission would be needed to transmit its power and torque to the driven wheels.

The use of four-wheel drive was decided in the earliest stages of the project and if this sounds like something of a departure for Bentley – which has only ever made rear-wheel drive cars in its past – it was felt that this new level of power demanded a commensurate level of control. Besides, if the Continental GT was to be exploited by its owners to its maximum potential, it would need to be not just useable, but utterly at home in all environments from the Santa Monica Boulevard to the compacted snow surfaces of Alpine resorts.

Nevertheless, in order to ensure that the right Bentley feel is communicated to the driver, Bentley’s powertrain and chassis engineers have experimented extensively with the distribution of torque to the front and rear axles. This has been done to provide the Continental GT with all the security of a four-wheel drive system but when appropriate, the added fun factor inherent within a rear-wheel drive layout.

Providing the link between the driven wheels and the engine is a six-speed automatic transmission built for Bentley by ZF and the first of its type in the world to be used in an ultra-high performance coupe. Firstly, the new transmission was modified by moving the differential forward, which allowed the drive shafts to be as far forward as possible, thus enabling the wheels to be close to the front of the car. But the defining characteristic of this transmission, apart from the use of six ratios, is its ability to lock its torque converter in normal driving, providing the same immediacy of response expected of manual transmissions. Despite this, shift quality is so good that often the most obvious evidence of a gearchange having taken place is the repositioning of the rev-counter needle.

Tiptronic actuation means that the car can be used either as a conventional automatic or as a clutchless manual where gearchanges take place only on command from the driver, via either the gear lever or paddles mounted behind the steering wheel. Naturally fail-safe mechanisms are incorporated to ensure it is not possible to over-rev the engine when changing down in tiptronic mode or stall the car by slowing too much in a high gear.

It is a fair observation that a 6-litre, twin-turbo engine with tremendous torque does not strictly need six gears to keep itself on the boil. Then again, to look at any element of Bentley performance in terms of need is perhaps to miss some of the point of the marque. It’s true that many Continental GT drivers will spend much of their time allowing the transmission to shift itself or even using the tiptronic function to lock the gearbox in a certain ratio and allow the engine’s massive torque to carry the car along. However, Bentley also knows that most of its customers for the Continental GT will be enthusiasts who will relish the prospect of flicking up and down the gearbox at the pull of a paddle or the push of a lever. Under the circumstances, six speeds seem entirely appropriate.

continues... | Part Three
Published 26 September 2002 Melanie Carter

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