Language Study

1.
For a simple description of mechanism and machines, we use ZERO conditional.
If/When the cylinder moves backwards and forwards, the driving wheel completes one full rotation.

Remember:
FORCE is APPLIED TO …
MOTION/MOVEMENT is TRANSMITTED e.g. Rotary motion of a cam is transmitted to a reciprocating movement of the connecting rod.

2.
Expressing cause and effect
The intake valve opens up, letting in air and moving the piston down.
(The intake valve opens up. It lets in air and moves the piston down.)

The piston moves back to the top, pushing out the exhaust.
(The piston moves back to the top. It pushes out the exhaust.)

As the piston reaches the top, fuel is injected. (The actions happen at the same time)