R8 V12 TDI: Audi unveils diesel supercar

We are the only company in the world who could do this,’ says Wolfgang Hatz, Audi’s powertrain development director, moments after the world premiere of the R8 V12 TDI Concept at this year’s Detroit motor show.

The very idea of a diesel supercar may be complete anathema to many enthusiasts, but according to Hatz it makes perfect sense for Audi to build such a car. With the twin-turbo 6-litre diesel V12 boasting 493bhp and 737lb ft of torque and promising 0-62mph in 4.2sec – all figures that overshadow the current 414bhp V8 petrol R8 – you can perhaps see his point.

The notion of a diesel-powered R8 range-topper has been bandied around at Audi since development of the diesel-powered R10 race car began in 2003, and it has been a particular obsession of VW Group supervisory board chairman Ferdinand Piëch ever since. Meanwhile, the R8 has proved hugely popular since its launch. Audi originally planned to build 2500 cars per year, but output will now be double that, and waiting in the wings to capitalise on this success are the V10 petrol R8, due later this year, and an R8 Spider (with a removable targa-type roof panel) due in 2009. However, the final decision on whether a diesel model will join them has yet to be made.

The world didn’t realise it at the time, but a V12 R8 concept car has already been shown – in the form of Lamborghini’s 2006 Miura concept, which was actually Audi’s first attempt at fitting a V12 engine into the R8 chassis. This latest concept is a step closer to a production V12 R8, but what, mechanically speaking, will be involved in making this exciting concept a reality?

‘The V12 diesel engine is around 100mm longer than the current petrol V8 engine,’ explains Hatz, ‘so the luggage space behind the seats will have to disappear. I also want to get the engine lower in the chassis than shown on this concept, so it will need to be dry-sumped to achieve this.’

Hatz also thinks he could improve upon the quoted power outputs of the V12 engine. ‘I haven’t driven the car yet,’ he says, ‘but we must make sure it is exciting to drive. I hope we can find some more power during development.’

The peak rev limit of 4500rpm is unlikely to rise much, though, as the pumping losses (the work required to get air into and out of the cylinders) outweigh any potential gain in horsepower beyond that point – even the R10 is limited to just 5500rpm.

Hatz would also like to find a way of reducing the overall weight gain. Fitting a V12 engine could add around 100kg over the V8 car, though at least the front/rear balance won’t suffer much as the engine mass moves closer to the middle of the car thanks to the longer engine and fixed gearbox position.

Speaking of gearboxes, Hatz wants to ditch the concept’s manual six-speeder in favour of an all-new DSG ’box that should be ready in time for the diesel R8, if it goes into production.

The concept shown at Detroit also featured Audi’s new ‘drive select’ dial, located around the starter button on the steering wheel, which enables the driver to adjust engine, transmission and damper settings in unison. Expect to see it on the V10 petrol R8 first before trickling down to the rest of the R8 range.

Unless Audi catches a cold due to the global slowdown then bet on the V12 diesel R8 appearing in showrooms from mid-2010. After all, if Professor Piëch can rubberstamp the 1000bhp Bugatti Veyron for production, doing the same for a diesel R8 should be a walk in the park.