The majority of modern cars are powered by four-stroke, internal combustion gasoline engines. This type of engine has been refined as automotive technology has continued to advance over the past century. While even the most basic car engine is a complex machine, the principles behind its operation are easy to understand.
Most modern cars use an internal combustion engine. More specifically, the reciprocating piston engine is most common. Engines of this type are often named for their size both in terms if overall interior volume and the number of cylinders. Cylinders can be arranged in several ways: a straight row (known as a straight or inline engine), directly opposite one another (a flat engine) or at an angle to one another (the popular V configuration). Thus, a 3.8L V6 is an engine with a total displacement of 3.8 liters and six cylinders arranged in two rows of three cylinders each. Engine volumes are also sometimes noted in terms of cubic inches or cubic centimeters.
Most engines use a four-stroke cycle. This engine cycle consists of intake, compression, combustion and exhaust. In the intake phase, fuel and air are drawn into one of the compression chambers. A piston rises in the chamber, compressing the mixture. The combustion phase begins when the compressed fuel mixture is ignited with a spark from the spark plug. The resulting explosion, known as the power stroke, forces the piston down and spins the crankshaft, thus powering the car. Finally, an exhaust valve opens to allow for the expulsion of exhaust and any fuel that did not burn.
Car engines experience a variety of problems. Some of these can be fixed simply, and others may make the engine permanently inoperable. Using gasoline with a low octane rating can result in engine knocking, which is actually a premature combustion in one of the cylinders. A cracked engine block is one of the more serious problems an engine can have. Blown head gaskets are more common, and can occur when an engine overheats or the gasket wears down. A broken connecting rod or faulty spark plug can leave an engine with one or more nonfunctional cylinders, robbing it of power.
While most car engines will eventually require major repair, a basic maintenance schedule should be followed to ensure that the engine lasts as long as possible and operates safely and efficiently. Regular oil changes are a must, as new oil will keep the engine lubricated and running smoothly. In addition, keeping an adequate level of engine coolant in the car will keep an engine from overheating. Occasionally spark plugs may need to be replaced. The engine air filter, which cleanses the air that is blended with fuel prior to combustion, is another item that should be changed as needed.
Besides the standard, gasoline-powered internal combustion engine, other types of engines are used in some cars. While the vast majority of engines are reciprocating piston engines as described here, rotary engines operate on similar principles but use a spinning rotor in place of a set of pistons to create compression. Diesel engines are similar to gasoline engines but are designed to burn diesel fuel, which is ignited with hot air instead of a spark. Cars that use alternative fuels, such as hydrogen or electricity, are also becoming more common.
