Kwi-revs ephantsi, intshukumo ephindaphindayo yeepiston ze-injini iyacotha, kwaye amandla okutsala ukutsala umxube kwiisilinda ayancipha. Ngeli xesha, i-valve yokungena kufuneka ivulwe ixesha elide kunokwenzeka, kwaye xa i-piston igijima kwiziko elisezantsi elifileyo kwaye ingena kwi-stroke yokunyanzeliswa, i-valve yokungena ivalwe ngokukhawuleza ukukhusela igesi edibeneyo ukuba ingaphumi. Ngelixa i-camshaft enecandelo elinqamlezayo "elibukhali" ivala ivalve yokungena ngokukhawuleza, i-"rounder" camshaft ithatha ixesha elide ukuvala. Ngoko ke, kwi-rpm ephantsi injini idinga i-camshaft "ebukhali".

Kwi-revs ephezulu, ipiston ye-injini iphinda ibuyele ngokukhawuleza, kwaye amandla okutsala ukutsala umxube kwi-cylinder yomelele. Naxa i-piston ibaleka ukuya kwindawo esezantsi efileyo kwaye sele iza kungena kwi-compression stroke, i-gas edibeneyo iya kukhwela kwi-cylinder ngeli xesha kwaye ayinakuphazanyiswa. Ngokuqinisekileyo yile nto siyifunayo, kuba ukuba ngaphezulu komxube kunokutsalwa kwi-cylinder, ngoko injini inokufumana amandla amaninzi. Ngeli xesha, kufuneka sigcine ivalve yokungena ivulekile xa ipiston iphakama, kwaye ungayivali okwangoku. "I-rounder" camshaft ngoku ikwindawo!

Imilo yecandelo lekhamera ye-injini inxulumene ngokusondeleyo nesantya senjini. Ukuyibeka ngokulula, kwii-revs eziphantsi sifuna i-camshaft "ebukhali"; kwii-revs eziphezulu sifuna "i-rounder" camshaft.