Four-stroke engine facts for kids

The four-stroke engine is an internal combustion engine. The four strokes are:

Stroke	Alias	Piston	Intake valve	Exhaust valve
intake	suck	opens, sucks in air + fuel	open	closed
compression	squeeze	closes, compressing the air + fuel	closed	closed
combustion	bang	opens, because air + fuel combust, expanding gas in cylinder	closed	closed
exhaust	blow	closes, blowing out the used gasses	closed	open

Images for kids

Four-stroke cycle used in gasoline/petrol engines: intake (1), compression (2), power (3), and exhaust (4). The right blue side is the intake port and the left brown side is the exhaust port. The cylinder wall is a thin sleeve surrounding the piston head which creates a space for the combustion of fuel and the genesis of mechanical energy.
An Otto Engine from 1880s US Manufacture
This 2004 Toyota Prius hybrid has an Atkinson-cycle engine as the petrol-electric hybrid engine
The Atkinson Gas Cycle
Audi Diesel R15 at Le Mans
Top dead center, before cycle begins
1 – Intake stroke
2 – Compression stroke
Fuel ignites
3 – Power stroke
4 – Exhaust stroke