4-Stroke Cycle Engine Theory Terms Ch 5

Four-stroke engine

Also known as Otto cycle. A combustion cycle that consists of an intake, a compression, a power; and an exhaust stroke. Also called four-stroke engine.

Two-stroke engine

An engine design that produces one power stroke for each revolution of the crankshaft.

Cross-scavenged

An engine with a special contour on the piston head, which acts as a baffle to deflect the air-fuel charge upward in the cylinder.

Valve overlap

An interval expressed in degrees where both valves of an engine cylinder are open at the same time.

Loop-scavenged engine

Engine in which the fuel transfer ports are shaped and located so that the incoming air-fuel mixture swirls.

Stroke

Movement of a piston in the cylinder from one end of its travel to the other.

Compression Stroke

Occurs as the piston moves upward in the cylinder with both valves closed. During this stroke, the air-fuel mixture is compressed into a smaller space.

Intake stroke

Piston stroke in which the piston travels downward in the cylinder with the intake valve open. This increases the volume above the piston and creates a partial vacuum that draws the air-fuel mixture into the cylinder.

Power stroke

Piston stroke that occurs when both valves are in the closed position and the force of combustion drives the piston downward.

Atomization

Process of breaking gasoline into tiny droplets and mixing it with air to produce the rapid burning required in an engine.

Exhaust Stroke

The fourth stroke in the four stroke cycle when the piston clears the unburned gasoline and waste gasses

Bottom end center

The lowest point of piston travel. Abbreviation is BDC.

Top dead center

The point at which the piston is at its upper most position on the compression stroke.

Internal combustion

an engine that burns fuel inside cylinders within the engine

Compression Ratio

Volume of combustion chamber at end of compression stroke as compared to volume of cylinder and chamber with piston on bottom center.