Bentley hopes new engines will help double sales

Instead, there is the deep growling sound of a V8 engine, which hammers its way into the car's leather-and-wood clad cabin.

It is the sound of things to come for the luxury car company; a new voice to sing a new tune to appeal to a new audience.

"We are widening the appeal," chairman and chief executive Wolfgang Duerheimer insists.

"We are introducing a completely new driving experience."

Since it was first launched about a decade ago, Bentley's Continental GT has become well known for its more powerful, yet at the same time more quiet and sophisticated, W-12 engine.

Engines are essential to Bentley's subtle diversification between cars that at first sight look similar. Hence, there is even a variety of versions of the drive systems that go with the W-12, which in its latest reincarnation has been installed in the new Continental GT Speed.

The car is the fastest Bentley yet, delivering nought to 60mph (100km/h) in just four seconds flat with a top speed of 205mph (329km/h).

"Bentley is now the world's largest producer of 12-cylinder engines," says Mr Duerheimer, ahead of the GT Speed's international debut at the Goodwood Festival of Speed.

With such a pedigree, Bentley's decision to kit out the Continental with a rather more brutal-sounding four litre V8 engine is a big deal in the world of luxury cars - its rawness ushering in Red Hot Chilli Peppers where Mozart previously reigned.

Big deal, that is, because the engine has enabled the British luxury car brand to penetrate new segments in this finely-sliced market.

"The V8 will appeal to a different market segment," says Michael Straughan, member of Bentley's board of management, in charge of manufacturing, pointing to how the V8 is a whopping 40% more efficient than the W-12 in terms of fuel economy and carbon dioxide emissions.

Yet in some markets it is the engine's torque, or pulling power, that is its main selling point.

"The reaction to the V8 has been superb, especially in the US," he says. "There's something about the Americans and the growl of a V8 engine."

By contrast, there is something distinctly British about how Bentleys are made at the carmaker's factory in Crewe, Cheshire.

Though output has expanded dramatically over the last decade, the techniques used remain largely the same.

Perhaps the most dramatic sensation within the Bentley plant is the wide array of smells, of leather and wood and sewing machine oil, as well as the sight of craftsmen at work in ways that bear no resemblance to the average car factory worker.

Leather-clad steering wheels are still stitched by hand, the seats are sewn from large cow hides using ordinary-looking sewing machines, exotic wood veneers are cut into shape with the aid of precision tools, and the stainless steel is polished by hand.

Staff at Bentley work 85-minute cycles, which means they have to learn a sequence of tasks that last for almost an hour-and-a-half, Mr Straughan explains. By comparison, mass market assembly line staff often repeat the same tasks every minute.

"Then if you add on the fact that we work with special materials that not many people work with now, you'll see why we've got to find people with the right skills," says Mr Straughan.

"People who have the mental capacity of remembering so much work and doing it to the same quality standard every time."

Such processes take time and make Bentleys expensive, though the carmaker's close link with the parent company Volkswagen Group helps it keep costs down.

"We're part of a global company with, I think, 96 factories around the world," says Mr Straughan. "So if we want to stay at the forefront of technology, which is crucial for Bentley, then we've got to take advantage of what's available within the group."

Using shared components while ensuring the cars made at Crewe remain distinct is a challenging balancing act, Mr Straughan acknowledges.

"We won't do it at the expense of the brand," he says. "The brand is the most important thing for Bentley."

Bentley has long taken advantage of the brand's appeal among the growing number of wealthy individuals, especially in emerging markets.

The Chinese market has helped sales recover from a recent slump and as growth is set to continue in markets such as Russia, India and Brazil, the carmaker is gunning for a doubling in sales over the next five years.

"Some 15,000 cars per year would be a reasonable volume for the products we've got at the moment," says Mr Straughan - which might not sound like a lot until you realise that these cars cost at least £140,000 ($220,000), and most of the time they cost a lot more.

Add to that its plans to broaden its product range, with the possible addition of a sports utility vehicle (SUV) that was launched as a concept at the Geneva motor show in March, and it is clear that the British marque's ambitions are as great as ever.

Bentley believes there is a market for ultra-luxurious SUVs that cost more than those currently on offer, such as the Range Rover, the BMW X5 or the Porsche Cayenne.

Rivals such as Maserati and Aston Martin have also seen this gap in the market and have come up with similar concepts over the last couple of years.

"Lots of people have talked about it," says Mr Straughan, "but nobody's quite got there yet, and we haven't got there yet.

"But there's a space there and it would be perfect for a Bentley."