Top 10 Diesel Engine Facts

Considering a diesel? Here are 10 fast facts about diesel engine power and technology.
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Chances are, your perception of a diesel engine includes one or both of the following visions: a hulking Peterbilt 18-wheeler parked next to you at a stoplight, its massive turbocharged diesel engine rattling not-so-softly, with the rumble from its giant chrome exhaust pipes vibrating the windows of your car. Or perhaps you envision a smoky old diesel-powered Mercedes-Benz, Peugeot, or Oldsmobile occupying the slow lane of the highway you're also on, doing its best to pull a long, slow grade, while smoking up a storm in the process. These are legitimate scenarios.

Fortunately, the clatter on diesels isn't what it used to be. Advances in engine technology, social change, and the transportation marketplace evolution have changed the roles that "oil burners" play, and immensely improved their behavior. Here are ten things you may not know about diesel power and the diesel engine in the truck—or car—sitting next to you:

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1. Diesel Engines Don't Use Spark Plugs

Most of the internal combustion engines in your life (your gasoline powered automobile, motorcycle, lawnmower and snowmobile) all require devices to ignite the air/fuel mixture in the engine's combustion chamber(s) and, in nearly every case, that device is a spark plug. Since diesels are "compression engines," meaning that the air/fuel cocktail is ignited as it's injected into the engine's cylinders at extremely high pressure, and under high compression, no spark plugs are needed.

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2. Diesels Have Raced at the Indianapolis 500

Diesel power has come and gone from Indiana's famous Brickyard numerous times, but never made a bigger splash than in 1952. Veteran driver Fred Agabashian put his Cummins Diesel Special on the pole for that year's 500 in a record-setting time-a major source of pride for the Indiana-based Cummins engine company.

It was a long, low, and decidedly fast front engined Kurtis roadster, benefiting from aerodynamic testing (not yet common in racing as it is now) and the use of a turbocharger on its nearly 400 cubic inch six-cylinder diesel engine (turbos didn't become commonplace at The Speedway until the late 1960s). But Cummins' dream of winning the 500 with a diesel were not meant to be; the air intake for the turbocharger was mounted low in the car's oval nose, and unfortunately became clogged with rubber bits from the track and other debris, overheating the turbo and ultimately the engine.

The car ran consistently in the top 10, failing on lap 71. Pit stops certainly wouldn't have been a problem, as the Number 28 Cummins-powered Kurtis carried enough fuel on board, and achieved good enough fuel mileage, to complete the entire 500 miles without a refill. It was the car's first and only competition outing, and the last time (to date) that a diesel has competed at Indianapolis.

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3. Mercedes-Benz Produced and Sold the World's First Production Diesel-Powered Automobile

The car was called the 260D, deriving power from a 2.6-liter four-cylinder diesel engine, and it came to market early in 1936. It developed just 45 horsepower at 3200 rpm, and set Mercedes-Benz on course to become one of the world's largest producers and sellers of diesel powered automobiles and trucks.

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4. Diesel Fuel Costs More Than Gasoline Because It Is More Expensive to Refine

Not really. Refining diesel fuel to meet America's "Ultra low sulfur diesel fuel" emissions standards does cost a bit more, but most of the price difference you see at the pump is due to more and higher taxes. In the U.S., diesel is taxed as an industrial fuel, which is taxed at a higher rate than consumer transportation fuels such as gasoline.

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5. Not All Diesel Fuel is Based on Petroleum Oil Pumped Out of the Ground

Its called biodiesel: diesel fuel that is refined from largely renewable sources. According to the National Biodiesel Board, biodiesel is America's first advanced biofuel, a renewable, clean-burning diesel replacement that is reducing U.S. dependence on foreign petroleum, creating green jobs and improving our environment. Made from an increasingly diverse mix of resources such as agricultural oils, recycled cooking oil and animal fats, biodiesel meets the strict specifications of ASTM D6751. As the world searches for non-petroleum based fuels, biodiesel may prove an answer.

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6. Don't Expect to See Vegetable Oil Pumps at Your Nearest McDonalds

It may sound tempting to run your car on recycled vegetable oil straight from the French fryer at the local fast food hangout. When fuel prices increase, it becomes popular to buy an old Mercedes-Benz and convert it to run on renewable fuels like canola or peanut oil. And what if the burger joint manager will give it to you for free? What a deal! But it's not the panacea it sounds like on the surface.

If the oil has been used, it contains particulates and other contaminants, which means it needs to be filtered before you pour it in your tank. A potentially slimy, greasy job at best. And it's also technically illegal too, because the EPA doesn't yet approve vegetable oil as a motor fuel. That day may come and, at some point, it may become more economically feasible to grow crops expressly for the purpose of refining them into government- approved motor fuel, but that's not yet the case.

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7. Diesel Engines Have Won the World's Most Prestigious Endurance Race

Audi has an enviable record at the famous 24 Hours of Le Mans in France. The great German brand first won Le Mans in 2000 then stunned the racing community a few years later with a turbocharged V-12 diesel (nicknamed the wooshmobile because it's so quiet), which packed a combination of fuel economy and power that could not be beaten. In the sport of endurance racing, superior fuel economy means less pit stops; less time wasted in the pits equates to faster lap times. That-combined with speed and mechanical reliability-is what wins long distance endurance racing marathons. Prior to Le Mans, the turbodiesel Audi's first race wins came on American soil earlier that same year, in Florida's 12 Hours of Sebring race. French automaker Peugeot has also since won Le Mans with diesel power.

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8. Diesel Engines Can't Use Carburetors

Fuel injection has replaced the carburetor in most of the world's new cars, but since a diesel's combustion process requires that a precise amount of air/fuel mixture be injected into the cylinders' high-compression combustion chamber at precisely the correct moment, that job is handled by high-pressure fuel injectors and/or a high-pressure fuel injection pump, either electronic or mechanical. Non-pressurized carburetors are not capable of doing this job in the ways required by a diesel.

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9. In Modern Locomotives, Diesel Engines Don't Drive the Wheels

Which is why they are most commonly referred to as "diesel-electric" locomotives. Today's modern diesel electric locomotives carry diesel engines putting out thousands of horsepower and equally massive amounts of torque (twisting force) that turn generators. The generators produce thousands of kilowatts of electricity, which is used by the locomotive's electric motors to turn its wheels. Some large pleasure boats, and other industrial watercraft, use similar types of power systems.

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10. The Inventor of the Diesel Engine Likely Committed Suicide

German engineer and inventor Rudolf Christian Karl Diesel was born in France in 1858. He developed and patented what we now call the diesel engine. On the evening of 29 September 1913, Herr Diesel boarded the post office steamer Dresden in Antwerp on his way to a meeting in London. After dinner, he was never again seen alive. A week and a half later, Diesel's body was found floating in the ocean. It could have been an accident that took place in the middle of the night, in the event Dr. Diesel took at late night walk on the ships deck, but his family and most biographers labeled his death a suicide. A few conspiracy theorists, however, maintain that he may have been murdered by competitors.

Today's Diesel-Engine Cars and Trucks

As of the 2011 model year, there are currently more than 20 different diesel-powered vehicle models offered by major manufacturers in the American consumer marketplace. More are coming over the next few years. Why not more, and why not sooner, given diesel's high power output efficiency and obvious fuel mileage advantage? There are several reasons that keep a bit of a lid on the diesel scene. Read more and see the list of diesel-engine cars and trucks on sale now. Click here.


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