I read the article about four stroke engines and how it works here -
http://www.animatedengines.com/otto.shtml
But one question remains, where is the energy comes for
1) Expansion before starting the engine cycle - I think its from battery. Please correct me if i am wrong.
2) After the engine cycle is started.
2) Once expanded from where the energy to compress comes from? I heard it compresses 1/8 to 1/25th of the volume of the air and it requires lots of energy.
Please let me know