If anyone has the means to add an extra direct injection and management system that can handle water, and increase the cam gear size so it is 3:1 to the crankshaft, and regrind the camshaft for 6-cycle operation we can have suck-squeeze-bang-blow-steam expansion-blow.
Six-stroke engine - Wikipedia, the free encyclopedia
It probably would have shown up by now if the EPA didn't frown upon the necessity of having to keep a water tank full on your car.