What would be the actual CC or CI of the engine to be able to acheive enough compression heat to ignite diesel or kerosene with no ether.
Kerosene auto ignites at 410 degrees F. ether auto ignites at 320 to 338F .

My guess would be something like a 60 to 80cc would do it but would it have preignition problems from using a crab instead of direct injection? Or would it work just like the ether/kero mix engines and be adjustable via contra piston.