Motor Musings

Greetings folks, and welcome to the fourth edition of Autos A-Z, your one-letter-at-a-time trip through the automotive alphabet.

In the past couple of weeks, we’ve covered ‘A’ - axles, ‘B’ - bearings, and ‘C’ - carbs; now it’s time for ‘D’ - diesel.

That’s diesel, as in Rudolph Diesel, not Vin Diesel.

At this point you might just be asking yourself, “who’s Rudolph Diesel? I thought this was an automotive website.” You’re right, and it is.

Rudolph Diesel is the man that the diesel engine is named for, although he didn’t power his first engine with (what is now known as) diesel fuel. Instead, he used powdered coal.

Vin Diesel is (supposedly) an actor, starring in such movies as xXx and the Chronicals of Riddick.

The big difference between diesel engines and traditional otto-cycle gasoline engines is that in a diesel engine the fuel is not injected until after the compression phase. This allows a much greater amount of compression, and therefore a greater efficiency. If you tried to compress a gasoline-air mixture that much, the fuel would pre-ignite due to compression heating. This can be explained by the ideal gas law.

This high compression ratio is also what gives diesel engines so much low-rpm torque compared to gasoline engines, therefore making them more suitable to heavy trucks and buses.

In summary

• Autos A-Z
• D is for diesel
• Rudolph Diesel invented an engine
• Vin Diesel is (supposedly) an actor
• Diesels are efficient

Any questions? Fire away in the comments.