The intake was/is made of phenolic.
Rotary engine ports are much like those of a two stroke engine as there are no valves. Simply put, there is only so tall you can make an intake port before it overlaps too much with the exhaust port when the rotor is turning and thereby both ports are open at the same time. This is why both intake and exhaust pulses are critical to rotary performance at the outer envelope. The way around this is to do what's called a "bridge port". This widens the intake port so more air/fuel can be stuffed in in a short period of time. It's equalivent to running a bigger valve for less duration in a piston engine. The "bridge" is an actual bridge that the corner seal of the rotor must ride on as the rotor face moves past the intake port. Without it, that corner seal would fall into the port and the rotor would no longer seal under compression. In any case, bridge ports can be very big, but because of rotor design can't be enlarged much to the inside. Therefore they must be done to the outside of the engine. This presents a problem because there is a water jacket to the outside. If the bridge port is really big, then epoxy is put into this water jacket and then ported to become a part of the intake port.
Port jobs that are tall and close to being too much will have the ever present "lope" like that heard on the 4 rotor video. This indicates that at idle the engine is right on the edge of even running because of the overlap between intake and exhaust ports.
Although the 4 rotor uses what is called peripheral ports where both the exhaust and the intake ports are in the rotor housing, not the side housings. The newer Renesis engines, by contrast, put both intake and exhaust in the side housings. Again because of rotor dynamics when turning, allows essentially, the ports to be open longer with less overlap. The peripheral port engine is traditionally for all out top end performace, and the Renesis is typically thought of for it's economy, although Mazda has proven that it can also boost HP substantially with the new Renesis design.
There are only a couple guys in the country that really know what they are doing when it comes to modifying rotary engine ports.
