Four Stroke Engine Basics The four stroke piston engine was first demonstrated by Karl Otto in 1876, hence it is also known as the Otto cycle. The technically correct term is actually four stroke cycle. The four stroke engine is probably the most common engine type nowadays. It powers almost all cars and trucks. The Radmax/Direct Charge Engine represents a dramatic departure from existing piston engine design that has not changed appreciably in well over 100 years. The four strokes of the cycle are intake, compression, power, and exhaust. On a piston internal combustion (or reciprocating) engine, each corresponds to one full stroke of the piston, therefore the complete cycle requires two revolutions of the crankshaft to complete. The RadMax™ Rotary Engine also uses the four stroke principle, however combustion chambers form between the rotor, outer housing walls, and vanes and their volumes change as the vanes move during rotation. Because the RadMax™ design has twelve vanes, the engine generates an incredible twenty-four combustion events (power strokes) per rotation, twelve on the upper side of the rotor and twelve on the lower side of the rotor. RadMax™ ROTARY ENGINE: RadMax™ ROTARY ENGINE "UNROLLED": Intake - The fuel/air mixture is injected through the intake port in the end housing, in to a "compartment" created between two vanes, the rotor and the outer housing walls. Compression - As the fuel/air mixture is swept along the cam the space between the vanes gets smaller, causing compression.   Power - Under high enough compression (diesel) or with either a glow or spark plug, the compressed fuel is ignited. As the fuel burns, it expands, driving the rotor forward. Exhaust - The exhaust exits through the exhaust port in the outer housing, as once again, the chamber narrows and the exhausted fuel is driven out of the compartment through a port in the end housing. This cycle takes place on both sides of the rotor for an incredible 24 power strokes per one revolution. This lets the RadMax™ engine generate 1 hp/ 0.75 lb, as compared to a conventional internal combustion engine's 1 hp/ 6 to 7 lb. Also note that the rotor and the vanes on the Radmax TM engine replace the 40 moving parts on a conventional engine, including timing gears, connecting rods, pistons, cylinders and valves. CONVENTIONAL PISTON (RECIPROCATING) ENGINE: Intake - During the intake stroke the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. Compression - As the piston rises the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture. Power - At the top of the compression stroke the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward. Exhaust - At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder.