The 100th anniversary of the Ford Model T is coming up. The fundamentals of the car, including the internal combustion engines that power most of them, have changed very little as far as their basic operations are concerned. An explosion happens in a cylinder, forcing a piston downward, that in turn spins a crankshaft mated to a transmission that spins a driveshaft that turns the wheels.

This is not to say advancement has not been drastic. Four-cylinder engines have gone from making 20 horsepower to more than 250 -- all while being more efficient and cleaner. New engine designs and advanced technologies make this possible, but all the technobabble can make things more than a little confusing for many folks. How are you supposed to know what a salesman means when he says the car he is trying to put you in is a direct-injected, turbocharged inline-four with variable valve timing, or has a clean diesel, or is capable of variable displacement?

Automobiles are hugely complex machines when viewed as a whole, but individual systems and parts are often governed by a few relatively simple principles. If you take your time and don't allow yourself to get intimidated, you might be surprised by what you can understand.

Read on for the basics on some current engine technologies that help make more power and improve efficiency.

Clean Diesel

Despite their far superior fuel economy, diesel cars have never been a popular choice in the U.S. That's because the first time diesel cars came to our shores in any real numbers, they rightfully earned a reputation as loud, stinky, slow machines. Since then, diesel technology has progressed greatly. No longer the compromises they once were, diesel cars are poised to make a comeback in the U.S., although diesel fuel's price premium might limit their appeal. Soon, many manufacturers will offer a diesel alternative for U.S. buyers, but without the noise, stink, or sluggishness. Even the Car and Driver favorite BMW 3-series will offer a diesel engine for 2009.

Old diesels produced exhaust fumes with significant amounts of oxides of nitrogen (NOx) and particulate matter (exhaust dust, or soot). The latest diesel catalysts successfully reduce NOx levels, making new diesels some of the cleanest cars on the road. A second device, known as a particulate trap, takes care of the airborne dust. The use of ultra-low-sulfur diesel fuel that the federal government now mandates also contributes to diesels cleaning up their act.

Direct Injection

Direct injection is not new to the automotive world, only new to gasoline engines for the masses. It has been the standard in diesel engines for some time. It differs from standard fuel injection, a.k.a. port injection, by injecting fuel directly into each of the already air-filled cylinders. Port-injected engines mix the air and fuel in the intake manifold -- if the engine is the car's lungs, think of the intake manifold as the mouth. Direct injection improves fuel efficiency and will generally yield more power when compared with a port-injected engine of similar displacement and design.

Fuel efficiency is improved because the system can more precisely regulate how much fuel is needed at any given time and can account for the minute differences among the individual cylinders. For example, if an engine is under light load (cruising on level ground or at idle), the injectors will wait until the last possible moment and inject a relatively small amount of fuel. Less fuel used equals greater efficiency.

At the other end of the spectrum is the power advantage. The direct-injected gasoline actually has a cooling effect on the cylinder, and engines breathing cooler air can make more power.

Next Page: Variable Displacement/Cylinder Deactivation, Turbochargers & Variable Valve Timing and Lift