This article is to investigate the inlet and exit pipe effect on a rotary engine performance. A 1-dimensional, three-cylinder reciprocating engine model was adopted to simulate the operation of a rotary engine with three separate chambers. The chamber volume variation in this model was identical to a real rotary engine. The test data of the real rotary engine were used as a benchmark test for this model. Various parameters are then studied, including pipe length, pipe diameters, and pipe shape with convergent/divergent angles. In the performance analysis, the results showed that the averaged performance data (BSFC, brake work, brake torque, pressure distribution) was within 5 % in tolerance. The results of pipe length variation showed that in a range of short inlet pipe brought higher power (8.4 %). On the contrary, the exhaust pipe had a better work output over a certain length (10%). With a shorter inlet pipe and a longer exhaust pipe, the work output makes about 14.3% higher. The results of pipe diameter variation showed that in a certain range, enlarging pipe diameter gained better work output (14%). The results of pipe shape appeared that convergent inlet pipe at a certain range had a better work output up to 11% more. Divergent exhaust pipe made slight gain in work. Under a specific rotational speed, well-tuning the air pipes in length, shape and diameter would enhance the engine work output 20% more.