exactly
I've driven many petrol and diesel cars. A diesel engine cant replace a real petrol engine even if its a R8 diesel engine or a BMW M3 diesel engine.

A M3 powered by a diesel engine would be blasphemy. But it doesn't mean that a diesel powered supercar would be blasphemy just because it doesn't run on petrol. Using diesel to power a supercar would be a nice alternative way of getting from 0-100km/h in 4+ sec.

IMO, the engine in the R8 will sound diesel. I've driven for instance the 400cdi when it was released, and it sounded awfully diesel, my bro has a 30d and it is 100% diesel with no real reving, and the peak power in the middle of the rev-counter, then it decreases... The 320cdi is fabulous, because it is very well damped and you almost hear nothing.

Modern diesels are fabulous: powerful, not so noisy any more, very torquey, very economical. Perfect on an E-Class or BMW 5er.
But they can't rev, they have no real redzone and if you rev them too long you loose power, and the noise is crappy.

So they lack the sportiness, imo. They are fast, powerful, no doubt. But not really sporty.

Nothing replaces the noise of a petrol, the power always increasing with the revving and ending in a thrilling, metallic sound when you hit the redzone... Or, in a different way, the terrific thunder of a big V8 angrily pushing you always further in a cataclysmic borborygm.

This is what an R8 (and any sportcat) is about. This what an diesel can't offer.
A diesel is...a bit emotionless. It does its work perfectly, often better than a petrol one. But the petrol engine has so much more soul, with its sound and reving power, it is just more sporty.

I love the word of W. Wiedeking, Porsche 's CEO:
"Pleasure begins at 4.000rpm. This is where a diesel ends."

Of course, to each its own, this is just my thinking about diesel!

Dream crusher!!!

To be honest such a torque producing beast is more suitable for luxury car like the coming A7 or a Bentley, perhaps even the Panamera.

Couldn't agree more with you about the benefits of a high reving V8 engine that runs on petrol but still, you can't really tell if a diesel powered high performance car would be total nonsense until you see one proving the opposite.

"Pleasure begins at 4.000rpm. This is where a diesel ends."

Lol I had not read that one before. Let's see what happens in the coming years. W. Wiedeking might have to swallow his words laters.

And yet BMW's relatively mass-produced inline-6 twin turbo reaches peak hp 400 rpm beyond this, and redlines at 5000 rpm.
It makes sense for the most frivolous of vehicles to minimize their emissions impact, if they are to survive in the long run. Diesel technology is already at an advanced stage for this to happen for supercars, so why not? Audi has considerable experience with the R10, and even if a 12-cylinder won't fit, perhaps a twin-turbo 8- or 10-cylinder diesel might. With enough exotic engineering befitting the R8, I don't see why 5500-6000 rpm is out of the question. This is much lower than the R8, yes. But for the "gentleman GT" driver who is drawn to the R8's overall exotic depth of engineering, the everyday concerns of economy, C02/congestion tax might outweigh the loss of the upper rev range. Not to mention the perfect (4-rings) marketing tool: R8 racecar begets R10 diesel racecar and inspires R8 roadcar, which begets a diesel variant.

For the power delivery and sound, the gap between petrol and diesel exists, but is closing. Look at some of the reviews for these diesels:

"Other than an occasional tyre drone, we can find little fault with the A5’s refinement. Even under hard acceleration only the slightest diesel chatter is audible."
-Autocar, A5 3.0TDI

"Try this. Cruise at 60mph, then tweak the throttle. Just a tweak, that’s all. Feel that? Instant response, linear as you like, with shove like no other 6 in normal use. With 62mph taking 6.3 seconds, this is a fast car – but all that torque means it’s real-world fast. It makes a mockery of all the flurried downchanges you need in an M6, and yet the other failing fast diesels can suffer – runaway, uncontrollable surge – is also metered. It’s like a very powerful petrol turbo (with similar response), and pretty addictive to boot. Other than at tickover and near 4,000rpm, it doesn’t even sound dieselly: the straight-six vocals are throbby, bassy and very smooth."
-Car Magazine, 635d

"the standing-start performance pales next to the 635d’s stomping in-gear ability. It gathers speed in truly impressive fashion; response is even better in the mid-range than down low...
Subjectively the 635d feels faster than the six-speed manual 650i’s 50-75mph fourth-gear split of 4.9sec. Much faster.
There’s more to the way the 635d drives than just its vast urge, however. The engine provides a wonderfully linear delivery of power from idle all the way to the red line. In this respect it is quite entertaining.
We wouldn't go so far as to say it's as spirited and enjoyable as its gasoline-engined siblings, but there's not much separating them. "
-Greg Kable for Autocar & AutoWeek, 635d

All reviews about recent diesel are amazed, because "we don't hear the clatter that much". So this is good NOT TO HEAR THE NOISE.
All reviews about big petrol are saying that the noise is fabulous, incredible, threatening, thundering...

This is a HUGE difference, between being happy not to hear the noise and having a fabulous noise...Isn't it? Especially for a supercar...That's why a diesel is perfect for a 635 or a E350.

But for a supercar you want something else than for a 635d...

Which is precisely why, were they to build it, Audi would specify a different kind of engine. Do you honestly think they'd put nothing more special than a 635d motor into their supercar? You do want something else than for a 635d and, knowing Audi, you can get it. After all, this is the company that has turned world expectation on its head at least twice in only a few short years.
The engine is only one aspect of the R8's appeal. The real ace up its sleeve is the combination of build quality (in and out), refinement, and enough balance and involvement to put even the 911 a notch down.

The reviews don't say you can't hear the engines. You just don't hear the traditional diesel sound as much. Again, this is with mass-produced engines that are capped at 5K rpm. Build a proper supercar-worthy diesel capable of 6K rpm, and see if there's a difference against the 635d.
Some of the noise quality is often down to exhaust tuning anway, but I'll grant that the magnitude is not there with a petrol. All the better to enjoy the B&O system when you're not hard on the throttle. Which is going to be most of the time.

Not all of the reviews for the R8 say that. If you look at the Car, Car & Driver, Autocar, etc. reviews, the sound is often mentioned only in passing or sometimes not at all. It is by no means a defining nature of the R8. Evo in at least two reviews has failed to even mention the R8's high-rpm sound. Others mention the sound when bringing up one of the car's few shortcomings. Car Magazine said:
"Yet the R8 sounds curiously quiet, unless you’re wringing its neck. You’ll have to drop to third or fourth for rapid progress at higher speeds, because the V8 is quite peaky. The forthcoming V10 version should address these quibbles, though."
As would a twin-turbo diesel, while getting better economy, lower CO2/congestion tax, and still living up to Audi's promise of the everyday supercar.

AutoCar is still saying that the concept, at least will be a V12 Diesel:

Two weeks before the Detroit motor show opens it doors, Audi’s star of the North American International Auto Show has leaked onto the internet – and according to early reports, it’s a 500bhp diesel-powered sports car.

The German car brand will show a design concept called the R8 V12 TDi at Detroit and, just as its name suggests, it’ll be a twelve-cylinder turbodiesel version of the critically acclaimed mid-engined R8.

Motor industry watchers have been anticipating a hotter version of the 414bhp R8 for some time now. Most of the speculation has been concerning a V10 petrol-engined option; Quattro GmbH boss Werner Frowein even confirmed that a ten-cylinder R8 will go into production. This is the first indication that a third R8 derivative is on the cards, though, which could also be fastest and most expensive.

Although there has been no official confirmation from Audi yet, the R8 V12 TDi should use the same 6.0-litre, twin-turbocharged V12 as the Q7. That motor produces a heady 500bhp and 738lb ft of torque between 1750- and 3000rpm. Bluetec technology means it’ll also be clean enough to meet Euro V emissions standards.

And performance should be beyond question. In the two-tonne-plus Q7, the 500bhp V12 TDi engine is strong enough for 0-62mph in 5.5sec; in a 1600kg R8, think 0-62mph in around 4.0sec dead, twinned with incredible in-gear acceleration and overtaking potential.

If the response to the hot diesel R8 is positive and Audi puts it into production, the R8 TDi will be a line in the sand in the development of the diesel motor car – the first true diesel-powered supercar, Audi could argue. Expect more on the car to emerge at its unveiling next weekend.


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