Combustion Engine Sex

Combustion Engine Sex is when you have anal sex with someone who has a poopy butt

So basically you ram your combustion cylinder into their valves and poop splatters all over your dick and on the floor and walls

Dave: hello mike dont wipe i wanna have some mad combustion engine sex
Mike: hell yeah lets get it
*mike goes to bed with poopy butt*
Dave: OHHH IM BOUTTA COMBUST
*coems*
*poop explodes everywhere*