Abstract: This invention called the IRICE uses rotational pistons (cystons). The IRICE is more efficient than a conventional piston engine by negating loses caused by reversal of the pistons in the engine bore. The IRICE contains two or more adjacent cystons with at least one head per cyston separating chambers contained in the housing between adjacent cyston heads. Cystons alternate their motions via a fluid or gas, called the pf, under pressure in relation to the pressure in adjacent chambers. The cyston(s) currently in motion, called the MOP cyston(s), contacts part of the IRICE, called the pushcan, producing torque. The cyston(s) static in relation to MOP(s) are called the SIP cyston(s). SIP's contacts a section of the IRICE called the clampcan that restricts it's motion allowing pf pressure in the chamber between the two aforementioned cyston's heads to exhort force moving the MOP cyston(s) and the pushcan to do work. Pf is moved through the IRICE chambers via inlets and outlets.