Audi is serious about making a diesel supercar. Kevin Hackett finds out what it would be like...
Speed, as we say at PistonHeads, matters. There’s simply nothing quite like it to make a driver feel alive; the sensation of dropping a gear, flooring the loud pedal and being pinned into your seat is what it’s all about for many of us. And what is the fuel we need for these thrills; the lead we need in our pencils; the blood we must have in our veins? Petrol.
Diesel? That’s the fuel for sales reps and blue-rinsed grannies isn’t it? Audi reckons not and, to make their point in the greatest possible style, they’ve invited a group of journalists to Miami so they can gauge opinion and decide whether or not to put their latest concept car into production. It is the world’s first diesel supercar: the R8 TDI Le Mans. Diesel. Just say the word out loud and think of all the connotations, the baggage that comes with it. Oily, smelly, dirty, rattly, slow – hardly the stuff of supercars, is it? But in recent years diesel cars have been experiencing something of a renaissance thanks to increased refinement levels and proper exploitation of the one thing diesel engines do better than their petrol-gulping equivalents: torque.
My biggest fear regarding the R8 TDI wasn’t whether it could perform like a true supercar but rather, when starting it from cold, if it would sound like a taxi. If the very notion of a diesel engine in a supercar has a problem then it’s to do with noise. And the normal R8 does sound good, with proper V8 burbles and grunts. Why risk ruining the things that make the R8 and cars like it so special? Well, after two successive wins at the Le Mans 24hrs using diesel power, the time is undoubtedly right for Audi to flex its muscles and show what this engineering can do for roadgoing sports cars. Some people believe that diesel is the fuel of Satan. And the Audi, as it basks in the welcome Miami sunshine, does look devilishly good. The team tasked with turning it into some sort of reality was made of just three people, headed by the man who is here to make sure this R8 doesn’t come to an untimely end: Thomas Kräuter.
He tells me they had only three months to build it once the project got the green light. There were problems initially because the V12 diesel lump is too big for the R8’s engine bay. So the rear bulkhead was shifted forward by 70mm to make room. Apart from sacrificing cabin space, there was no room to fit sound insulation so the risk of this car sounding like a bag of spanners is starting to look very real. Cooling was an issue too, neatly addressed by incorporating massive air intakes in the nose, larger side-blades and extra scoops along the flanks, and a big NACA duct on the funky glass roof which channels air straight into the engine. Kräuter reckons a production version would be less fussy but I really like the look of this thing.
When the car was star of the recent Detroit and Geneva motor shows, it had different wheels but otherwise it remains the same. Behind the standard R8 alloys are huge carbon fibre brakes and there’s an aluminium strip that links the front and rear diffusers.
This metal trim makes the diesel R8 look lower than normal, but it’s an optical illusion. Open the driver’s door and it’s all very familiar R8 inside – which is a relief. On the steering wheel is a red start/stop button sitting atop a three-position lever which controls the ride settings. Press the button once and the instrument needles swing from left to right and back again. It looks fancy and takes barely a second but in that time something very important has happened: the heater plugs have warmed the V12’s combustion chambers.
With another prod of the red button, the starter motor whirrs and ignites six litres of Le Mans-developed engineering. My fears of it sounding like a diesel prove unfounded because, honestly, there’s very little sound at all, apart from the whooshing of air and soft whirring of the mechanical bits doing their stuff. Even without any sound insulation, the noise is incredibly refined and rather difficult to describe; which, for a writer, is a bit of a nightmare.
Setting off for a bit of Miami freeway action, a Highway Patrol officer kindly keeps the traffic back and I’m treated to a wide, open, empty stretch of Florida’s finest road surfaces.
I still have the car’s chaperone next to me and he’s here to make sure I don’t disintegrate the temporary A4 transmission with full-bore standing starts. He requests I take it easy through first and second but after that I can take the revs a lot higher. Into third and I floor the throttle. Instantly the R8 devours the road, tearing toward the horizon. The noise changes too, with all that cooling air being sucked in over our heads, it’s like being inside a jet fighter. The effect is quite astonishing and this is with the engine de-tuned to half its potential. With the limits removed it would produce 738 lb ft (1000Nm) of twist. At 55mph I back off, safe in the knowledge that this unique car’s gearbox is still in one piece and that the potential for truly huge speed is definitely there for the taking.
To put this R8’s torque output into some sort of perspective, a normal R8 musters less than half that and a new 911 Turbo has 457 lb ft. So it should be obvious that this R8 provides a unique driving experience – and it is. Of course, it won’t be for everyone and Audi knows that. That a normal R8 revs to 8250rpm and this one redlines at 5000rpm will be enough to dissuade huge numbers from reaching into their pockets. However, to dismiss this concept because it’s different would be foolish. It’s quite an achievement and I sincerely hope it reaches production because the technology and the engineering packed into it are astonishing. Audi reckons it’ll return an average of 28.5mpg, but it’s up to you if you think that economy is important in a supercar.
Speed matters; of course it does. But when diesel power is this damn good, this refined, perhaps it’s worth putting on the rubber gloves at the filling station – somewhere we’ll be visiting less frequently in future by the looks of things. Just two words for the guys at Audi: build it.