How Gas-Powered Cars Work

Gasoline Power

Gasoline-powered internal combustion cars require fuel that is stored in a tank near the rear of the automobile. A fuel pump brings the gasoline to the engine via a fuel line. Gasoline-powered automobile engines are generally classified as a four-stroke type.

Four-Stroke Engines

The engine's pistons work up and down. For every four strokes of the pistons, only one is a power stroke. A four-stroke cycle, also called the "Otto Cycle," includes "up-down-up-down." The typical four-stroke engine includes the crankshaft, connecting rod, one or more camshafts, and the valves. The engines also have one or more cylinders, each of which has a spark plug, piston and crank pin. Each up and down movement of these cylinders is called a stroke. The power stroke is the movement of the air and gasoline mixture from the fuel injection system into the cylinder to be ignited by the spark plug. Valves regulate the amount of fuel and gasoline brought into the combustion chamber, which has outlets to vent the exhaust.

Intake

Internal combustion engines operate in a chamber (cylinder), using air as an oxidizer. Air is taken in from outside of the car, and the fuel pump brings gasoline into the combustion chamber. The first stroke of the piston brings in fuel vapors and air. This air and gas mixture is then held inside the cylinders. A typical engine has four to eight cylinders, but engines have been designed and produced using anything from 1 to 36 cylinders. Engines with more cylinders run more smoothly and have greater power and torque, but the extra cylinders add weight to the car and significantly reduce fuel efficiency.

Compression and Combustion

The lead-acid battery located in the engine well and an induction coil provide an electrical spark that burns the air and fuel in the cylinders. The gasoline and air mixture, expanding while heated, is put under extreme pressure. The battery is continually recharged while the engine is in use by the engine's alternator (or a generator in some models). The spark must be perfectly timed or the engine will not run smoothly. The spark timing is done by the fuel injection system. The combustion and expansion of the gases creates the pressure that moves the engine's piston rods and the crankshaft. A flywheel, attached to the crank, regulates the engine balance.

Exhaust

Leftover elements from the combustion are pushed out of the engine through the exhaust system. Most new cars filter this exhaust through a catalytic converter to remove a portion of the polluting chemicals and gases. A significant amount of gasoline vapor, left in the chamber, is pushed out into the air. Particulate matter, sulfur oxides and dioxides, carbon dioxide and soot are all released from the engine.

Resources

• Online engine simulation