How a Car Works: Pistons

What components make up a piston assembly?

A piston and a connecting rod.

What is the function of the piston?

It moves up and down inside the cylinder.

What connects the piston to the connecting rod?

The wrist pin (also called a piston pin or gudgeon pin).

What is the purpose of the connecting rod?

To connect the piston to the crankshaft and transfer force between them.

What is the rod cap?

The removable bottom section of the connecting rod that allows it to be fitted onto the crankshaft.

What is the top surface of the piston called?

The crown.

What role does the piston crown play?

It forms the bottom of the combustion chamber.

Which part of the piston experiences the highest temperatures?

The crown.

Do piston crowns all have the same shape?

No, crowns come in different shapes depending on engine design.

What is the side portion of the piston called?

The skirt.

What is the function of the piston skirt?

It slides against the cylinder wall and helps keep the piston aligned.

Why should pistons be lightweight?

To reduce inertia and help maintain momentum at high engine speeds.

How many piston rings does a typical piston have?

Three rings.

What are the top two piston rings called?

Compression rings.

What is the purpose of the compression rings?

To maintain a gas-tight seal between the piston and cylinder wall.

Why is a gas-tight seal important?

It prevents combustion gases from escaping past the piston.

What is the bottom piston ring called?

The oil control ring.

What is the purpose of the oil control ring?

To maintain a thin film of oil on the cylinder wall.

Why is a film of oil needed on the cylinder wall?

To reduce friction and wear between the piston and cylinder.

What major engine component is connected to the piston by the connecting rod?

The crankshaft.