Purely by curiosity I'm looking into how a car engine works. And the different explanations I get about the four-stroke cycle are pretty simlple to get :
While the piston is going downwards and making space in the cylinder, the intake valve opens and lets a mixture of air and gasoline fill that space. On its way back up, the piston compresses the mixture and the spark plug ignites it. The oxygen from the air and the hydrocarbons in the fuel then react and become vapor and carbon dioxide, which for some reason rises the pressure and forces the piston to go back down. When the piston comes back up, the exhaust valve opens and lets all of the used gases out.
What I don't get is :
-What makes the intake valve open when the piston is on its way down ? Is it just the drop in air pressure inside the cylinder caused by the piston's movement that "sucks" it open ?
-What causes the piston's first down-and-up movement ? Is it kinetic energy from the previous cycle ?
-How does the ignition happen at the right time ?
-What makes the exhaust valve open when the piston comes up after the ignition of the mixture ? If it's the pressure inside the cylinder due to piston's movement, then it should also open during the compression of the mixture, which wouldn't serve much use...
Thx in advance