There are three general types of two cycle induction. The most simple type of air intake induction is called a piston port engine. This type of two stroke engine has holes cut through the cylinder walls in specific areas. The second type of induction, and the most popular type, is reed block induction. This consists of multiple reed petals that allow air into the crankcase and keep it trapped there. The third type of two stroke induction is generally used in rotax two cylinder engines is the rotary valve engine. It does slightly better than reed engine because there is no restriction from reed petals. The rotary valve rotates past the crankcase intake port at a specific time to allow air through then seal the air into the crankcase.
A rotary valve engine is always a two stroke engine. Most rotary valve engines are rotax engines. Although other rotary engines such as suzuki and kawasaki have been made. Rotax engines are used in snowmobiles, jet-skis and motorcycles and aircraft engines. A rotary valve refers to the intake of a two stroke engine. There are three types of intake designs for two stroke engines. Simplistic two strokes are piston port, meaning that the piston movement past the port controls the incoming air timing. The piston port engine doesn’t do a very good job of keeping the airflow to stay in the engine. The air can simply travel back out of the engine. The most popular intake air induction is the reed port engine. It uses reed petals to allow the intake air in the engine and traps it there. The tension of the reed petals can change with the use of different petals and can provide some power improvement at certain rpm ranges. A rotary valve engine has the best intake air control.
Rotary engines have the ability to make large power gains through tuning. One of the most important aspects of rotary tuning is rotary exhaust. Rotary engines produce very strong hot pulses of air. The strong exhaust pulses can be used in a manner similar to two stroke exhaust tuning. The exhaust can be tuned to scavenge the intake air into the engine causing a filling of air into the intake side. The intake air is trying to fill the vacuum of where the exhaust has left. Racing headers from companies like racing beat and mazdaspeed can bring large improvements in power. Muffler and larger tubing mandrel bent exhausts can also largely improve the power of a rotary engine. Rotary exhausts should not be cheap normal exhausts. The increased temperatures and pressures of the rotary exhaust will quickly break or destroy a normal exhaust. The preferred exhaust systems will be larger gauge (thicker) and best made of stainless steel. Even the mufflers are made thicker and welded better. Horsepower gains will vary on regular and turbocharged cars but will be substantial on both types of vehicles. Some rotaries may experience over 10% power increases! This is the first place to look for performance in a rotary powered vehicle.