So...open the hood & you'll see a bunch of metal stuff: tubes, compartments, wires; it looks like a metal piece undergoing surgery or something! The purpose of the engine is to combust gasoline & convert the heat energy produced into mechanical energy (remember how energy can't be created/destroyed but can be converted?). Combustion occurs within the engine; hence it's an internal combustion engine. There are external combustion engines, such as the steam engines used in old-fashioned trains. However external combusion engines are less effective than internal combustion engines; that's why we don't see much of the former these days.
WTF is this...
The most common engine system is the 4-stroke combustion cycle, also known as the Otto cycle.
- Intake: the piston starts at the top - intake valve opens- piston moves down - takes in a cylinderful of gasoline & air.
- Compression: the piston moves down - compresses the air & gasoline mixture.
- Combustion: the piston moves up again & hits top of stroke - the spark plug emits a spark - ignites the air & gasoline mixture - gasoline charge combusts/"explodes" - the piston is driven down.
- Exhaust: piston hits bottom of stroke - exhaust valve opens - exhaust leaves chamber.
The piston is connected to the crankshaft by a connecting rod. The motion produced is rotational which fits perfectly to move the car's wheels. The piston moves up & down in a cylinder; there are usually more than 1 cylinder used in vehicles today.
So you turn the ignition key & the engine doesn't stuff. Why does it happen? There are several reasons:
- Bad fuel mix: insufficient fuel/clogged air intake.
- Lack of compression: worn piston rings/hole in cylinder.
- Lack of spark: inaccurate timing/worn or broken spark wire/plug.
- Clogged exhaust.
You can learn too!
It is good to know what happens in that car of yours; knowledge couldn't hurt. Take some time to read up online or offline about the mechanism (since I'm no mechanic); it could be handy one day ;)