You need to keep some space between the stuff you want to stick to the piston and the stuff you don't want to stick. Also, I think WALL element just absorb the stuff that gets pistoned into it. It might work for your engine. Is hard to say exactly what will work without seeing the save.
ok i recreated this from memory since i deleted it, its still in beta though
this one without gas to see what its SUPPOSED to work like
im sorry dom, but thats not what i was looking for,
1.) the gas ignited, something easily fixed
2.) my plan was a 2 stroke engine, that was a fire valve type thing
3.)its open topped
i know i should of told you my plan and no offence to you, but thats not how i want it
thanks for trying :)