Rotary Porting.
It was asked for so here is a pretty good run down of different ports used. There are shops that have their own variations also.
ENGINE PORTING
Aside from adding a turbo or supercharger to a rotary engine, the only other way to increase performance is by porting the intake section of the engine. Porting a rotary engine is a way to extract more power from it, although often, the bigger the port the less drivable and practical the engine is. There are several different types of porting available for the rotary engine, ranging from mild all the way to the peripheral port. While porting is still a popular engine modification, in recent years, the 13B Turbo motor has taken over as the main engine conversion for many older Mazdas, mainly due to their lower prices and increased reliability. But nothing can really beat the sound of a good ported rotary.
This is a guide to the different types of porting available and what their 'pro's' and con's' are.
From Mazdatrix:
"In a Rotary engine, the port timing is equivalent to a camshaft in a piston engine. The higher the top of the port, the later the intake or exhaust is closing, and the longer the duration. On the exhaust port, the lower the bottom is, the sooner the port opens, and the longer the duration is. On the intake, the opening is the outer side of the port - which can NOT be changed much (the corner seal needs that area) without going to a bridge port.
We are not going to get into the various pluses and minuses of the different ports here - way too much could be written on them, so we may get into that at a later time, in another section.
Porting is very time consuming, but the more you do, the faster it gets. There are definite techniques involved, that only practice will develop."
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