madaz matt

After reading a couple of posts about porting the exhaust alot wider, the main problem is that the wider you go the less suport the apex seal has, my thoughts where if some how you could had a brige in the middle of the port or mabe two briges alowing you to go alot wider without fear of dropping an apex seal. this could eazely be done with rx8 housings. i got the idea from a mag that said that they were going to try it with p port intake. any thoughts apreciated.

RONIN FC

Thats a hot place to have a thin strand of aluminum.

Lynn E. Hanover

Even in 2 cycle cylinders the vertical webs that support the ring in the center of the exhaust port often become deformed from the heat involved. Better to add a slight radius the engine side of the vertical but leave the body full width. But the rotary generally has higher EGTs, so not a good idea.



Also, there is little need to go much wider at all. And the apex seal (3MM) is very rigid and can span a much wider opening than you need to build.



The exhaust is still under a great amount of pressure when the ports are uncovered. A large amount of the total flow available will happen just after the port opens. So the port shape at the opening line is very important, and not much else is. So if the port is wider, (bigger cross sectional area per degree of rotation)the shape is even more important. So a radius at the open line and up the sides a bit, and little else matters.



So any shape that is smooth at the opening line (bellmouthed) straight from the open line to the port face.

And has a bit of a straight run in the exhaust tubing before the first bend, will flow like a jet engine.

This first flow after the opening, will be supersonic. Any deveation from a straight line and polished like chrome finish is less than ideal. Drag increases at the cube of velocity, so smoothness in exhaust flow is much more important than most people think.



Note that the first engines (10-A) had three round holes for exhaust ports. Not good enough for high revs?

Formula one engines have less area and turn over 20,000 RPM. So even the three holes are more than enough.





Lynn E. Hanover