A diesel engine has a compression ratio of (Volkswagon) 23.5 to one. That means that at normal operating temperature
the air is heated enough by the compression so that the diesel will ignite and burn just from the air temperature! If you let, for example, something out of a container (butane, hair spray),
it will get cool or even cold as the pressure drops. The reverse is also true; a gaseous substance will get warm or even hot if you increase the pressure. All you have
to do is inject the diesel into this heated air at the right time. Thus no ignition components in a diesel engine. No 13.5 to 1 air to fuel ratio; no fuel mixture. There is no throttle
plate. The engine is always getting the maximum amount of air it can take in; only the amount of diesel sprayed into the cylinder
changes. Because of the high temperature in the cylinder, virtually every atom of fuel combines with air. No emissions test
during inspection (in this state, at least). It will run completely under water as long as the intake and exhaust are clear.
Since diesel has lots of wax in it, a diesel engine achieves extremely high fuel efficiency. Diesel , by definition, burns
instead of exploding, which is gentler on engine components. Furthermore, diesel has lubricating properties and a diesel engine
is likely to last hundreds of thousands of miles before needing to be rebuilt.
Volkswagon now offers a 1.9 diesel engine. Look for TDI, which stands for Turbo Direct Injection. Since the motor has
more displacement and is turbo-charged (a diesel engine can't get enough air!), it has a VERY respectable 115 horsepower nowadays. The top of the piston is shaped in a way that swirls the
air around like a miniature cylone and the diesel is inected under extremely high pressure. There is no heat wasted in a pre-combustion chamber like there is in an indirectly injected (IDI)
diesel engine. My Rabbit, in comparison, has only 52 horsepower and does just fine; it'll go 85 mph. The TDI, though, is STILL about 20% more efficient than the IDI engine in my Rabbit!
And if you want to get really radical, look on the right!