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Diesels – Destroying Three Decades of Stereotypes Twelve Hours


VehicleVoice correspondent and AutoPacific Vice President Jim Hall attended the 12-hours of Sebring in February. Audi won the race with its revolutionary R10 diesel-powered racer. Jim provides an interesting perspective on diesels in the USA and the future.
Diesel cars are nothing new in America. Oil-fueled Mercedes of various numeric monikers have been sold in this country since the mid-fifties. With a reputation (earned) of being near indestructible and overengineered to the nth degree and the reality of superior fuel economy to comparable 1950s and 1960s cars, the slow but parsimonious engine gained a following of bunker oil enthusiasts who were forced to buy Mercedes-Benzes and a little later Peugeots. Still, the loyal didn’t mind the fact their cars were pokey, noisy and smelled emitted sooty, funny smelling exhaust.

American Diesel Engine Debacle – Launching Not Ready for Prime Time Diesels
Following the first energy crisis of 1973, the allure of reduced fuel consumption promised by Rudolf Diesel’s compression-ignition engine led major automakers across the globe to begin diesel engine development in earnest. Among those companies were GM and Volkswagen. In an effort to bring the economical joys of compression-ignition driving to the masses, both companies took an innovative, albeit hazardous, approach to developing their new diesels… they started with a conventional Otto cycle (i.e. gasoline) engine and would modify it into a diesel. Prior to this point all passenger car diesel engines were designed as diesels from the ground up. Extremely high compression ratios and pressures in the combustion chamber mandated notably rugged cylinder block, piston, connecting rod and crankshaft design. Far beyond the norm for a gas powerplant. This is the primary reason for the diesel engine’s reputation for durability, they were historically overengineered to a fare-thee-well. On the downside, normally aspirated diesel engines came up short on the horsepower side of the equation when compared with a comparably sized gasoline engine of similar configuration. A pleasant side effect of Herr Diesel’s compression-ignition process is the generation of an inordinate level of torque for a given engine displacement.
As history has shown, the gasoline V8 (and later V6) engines GM had functionally “converted” into diesel powerplants as well as VW’s SOHC inline-4 brought new meaning to the phrase hangar queen. Failed connecting rods, distorted cylinder blocks and spun main bearings were common. Not equipped with a water separator for cost reasons, water contamination of the fuel was rampant among GM’s diesel Oldsmobiles, Chevy’s, Pontiacs, Buicks and Cadillacs in humid climates.
With neither spark plugs nor a distributor, diesels were sold as “never requiring a tune-up.” While that was true from the standpoint of the ignition system, the remaining systems of the engine did require maintenance. Maintenance that was quite often forgotten or ignored completely. The only problem was that in the hands of American motorists, these “converted” diesels exhibited all the robustness of a potato chip. Not long after the mid-1970s debut of converted engines, the reputation of all diesel powerplants took a nosedive. By the early 1980s, the diesel car for the masses faded from view and just about the only folks buying diesel cars were the same diesel traditionalists who bought before the ’73 oil crisis. It seems they still didn’t mind driving cars possessed with less than the normal dose of performance. Cars that clattered and rattled and generated smelly exhaust.


So, You Think Diesels are Popular?
Other than the application of turbocharged diesels in heavy-duty pickups and some full-size SUV, the diesel passenger car has become but a minor addendum to the sale charts over than last twenty years or so. If you think diesels are popular in today’s new light vehicle market, you’re most likely driving a pick-em-up.

But this hasn’t detered Audi. In fact the company is seriously interested in plying the North American car market with new-technology diesels.
Enough Folderol… Now On to the STORY
In early 2006, Audi debuted a V12 turbocharged diesel race car that will run in the 24 Hours of Le Mans endurance race in June. The car first turned a wheel in anger at the Sebring 12 Hour American Le Mans Series opener. On Saturday March 19, 2006 one of the oil-fueled race cars took the checkered flag a little more than twelve hours after the official start of the race. During those twelve hours, the Audi R10 pretty much destroyed every diesel stereotype in the book.

Diesels are loud and rattle The compression-ignition engine is said to be noisy and clattery. The Audi V12 was by far and away the closest thing to a silent car on the track. Whisper quiet as a matter of fact compared to the shrill high-pitched shriek of the the V8 Porsche RS Spyder prototypes. After the race, a driver of one of the class-winning Corvette C6Rs said “You couldn’t hear the Audis coming up on you.”

Diesels have smokey and sooty exhaust. Diesel fuel quality has improved in Europe and other markets over the years, the reduction of sulphur in the fuel along with more precise direct fuel injection has eliminated the majority of the so-called diesel soot. The small particulates that are a result of compression-ignition combustion are now handled with sophisticated exhaust after-treatment in the form of particulate trap/burner mufflers on modern diesel passenger cars. Such a high-tech muffler was fitted to the R10 leaving its exhaust freer of soot than that of the aforementioned Porsche RS Spiders.

Diesels make no power After twelve hours of dominating the Sebring race, it’s pretty clear power was never in short supply in the Audi R10.

Expect Audi of America to Sell Diesels
Audi isn’t spending copious amounts of cash on racing a diesel just for fun. The firm wants to sell modern diesels on this side of the Atlantic. Look for a 233HP 3.0L V6 diesel to join the powertrain lineup in the company’s Q7 crossover around the middle of next year. Late in 2007 Audi is expected to add a 4.2L 326HP diesel V8 to the Q7 as well as the companies A8 flagship sedan. If the oil-fueled engines meet with a favorable response, you can expect the 3.0L V6 engine to be offered in the mid-range A6 as well as the next generation versions of the A4.
Which is all fine and good. But give me Audi’s upcoming mid-engined R8 sports car with a diesel engine like the V12 in the R10, and I’d be one happy camper.
Of course, the fuel is still kinda smelly and messy.

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