Rotary Engine Porting
Choosing a Port
Generally ports that have grinding around the normal boundaries will be for a racing motor. But still some are streetable. You’ll typically find bridge ports, j-ports, monster ports, and peripheral parts in racing applications. They are all more or less in the same category because most of them use a bridge of material on the plates (side housings) that supports the corner seals as it passes over it.
The effect is a separate port opening which is on the surface to the outside of the normal port, although the runner will be shared with the typical port opening. A regular bridge port will not compromise the rotor housing’s water seals between plates, but the rotor housing might get notched to make the most of the port volume.
The J-port is a bit larger type of bridge port that does compromise the water seals. Despite this, it does not go completely into the water passages behind them. Engine builders use silicone-based sealant to prevent coolant seeping out of the water jackets.
The monster port does go all the way into the water jacket and will require some degree of back filling to block off the coolant from the port. This is used with the addition of sealant.
These can be referred to semi-peripheral ports because of the large amount of 'match porting' (notching) done to the rotor housing, which provides a straighter/larger air path. Peripheral ports dispense with the side ports completely. They will bring the intake charge through a large hole in the side of the rotor housing. Every time we step towards the extreme, it increases the engine’s top-end power, reducing low end torque, and it narrows the engine's power curve.
So basically, if you are going to use your rotary car on the streets you'll most likely want a mild or extended port. Also known as a small or large street port. If you have a tubrocharger you'll want one of theses ports for street use. For race motors consult your rotary engine builder.
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