Study the car structure

I borrowed a CAR structure book from the mini library near by our house and Hong Zheng loves this book.

I brought him to his uncle's car workshop and tell him each part of the engine and how the engine works.

When Hong Zheng saw the engine, he will starts to mumble like :" When the spark plugs sparks, the explosion will press down the piston, the piston will turn the crankshalf and move the wheels." Although not very clear but i can know he was describing right.