I first found this in Automotive Engineering International (SAE), and took it to be a side project or experiment. But now I think Audi is pretty serious. Here is one link I found with the help of google search terms "audi Le mans diesel". http://www.edmunds.com/insideline/do/Features/articleId=109326 I may watch a little more of the Le Mans racing this year!
I think the biggest problem with diesel right now is that it's still more expensive than regular unleaded. Once bio-diesel or something similar goes mainstream it will probably stay that way. The other cool thing is most companies have found a way to get rid of the horrible ticking noises from the large amount of pressures required to ignite the mixture.
Diesel has many advantages over gasoline. The more I have learned about them, the more I like them. Gasoline became more popular because back in the day, Diesels had no top end. All torque and not HP. Thanks to turbochargers, that has all changed. Driving the newer Powerstrokes, Duramaxxes, and Cummins, makes me want one.
Read up on some of the European diesels guys -- BMW and Mercedes have some incredible diesels that they don't bring over here. Part of the reason is because of emissions regs. And part of the reason is because the market over here hasn't accepted diesels in cars. But as more people have them in trucks, the market for cars will be bigger. We also have to develop the refining and fueling capacity for more cars to run on diesel. Done like BMW and Mercedes, they make great street motors - enough power, gobs of torque and great mileage. Diesels benefit from higher specific energy of the fuel (more btu's/gallon than gasoline), the much higher compression ratio (18-20:1 is common) and reduced pumping losses because they don't have a throttle. They're much more efficient especially in city driving and under heavy load. BMW's new performance oriented twin-turbo 3.0L (183 cubic inches) six cylinder diesel makes 270HP at 4400 rpm, and 415 lb-ft of torque at 2000 rpm! It makes at least 390 lb-ft of torque from as low as 1500 rpm. It's got bottom. It's useful redline is 5000 rpm - amazingly high for a diesel. It accelerates the 4000 lb. 535 sedan to 100 km/hr (62 mph) in 6.5 seconds, and the car is electronically limited to 155 mph. It uses a small turbo to boost low rpm output, and a second larger turbo for high rpm output. If they were available over here, I'd have one in a heart beat. The 4000 lb. car gets around 28 mpg in the city, and mid 30's on the highway. A comparable 5.0L engine would put out about 450HP, and 700 lb-ft of torque! The 'ticking' noise or clatter you hear at idle is essentially the sound of 'detonation', or self-ignition if you like. They have gotten better at reducing what you hear - mainly with sound insulation - but it will always be a part of a diesel to some extent. In Europe where fuel is 3 - 4 times as expensive as it is here in the States, diesels have always ruled, even in cars. It will be interesting to see how Audi does at LeMans - V12 5.5L diesel - about 650 HP, 850 lb-ft of torque and an operating range of 3500-5000 rpm. They had to rethink the driveline and the tires to deal with the MUCH higher torques than they're used to. Early tests show the car to be as fast as the gasoline powered racers from last year, and about 40% more fuel efficient - less pit stops. It's also much quieter which means less tiring for the drivers. They even put particulate traps on the racer - so it won't smoke black.
