Ok, well "I" wont be building this engine, but having someone else do it.. but before I just hand it over I would like to have a discussion on what would be the best size and location for the p-ports? I have build a few 13Bs and done a few streetports, but I dont feel I have the experience/equipment necessary to put together a strong reliable p-port engine. 1st off, this will be a 20B engine, setup with S5 N/A rotors running N/A, with ITBs and controlled my a haltech. It is also going to be a street engine, so a decent idle and rpm range is a must, I would like it if I didnt have to spin the engine over 9k. I have spend hours searching and reading over many, many posts and pictures of others ports, as well as talking to a few differnt builders (pineapple, RB), and feel really good about what can become of this engine, but I wanted to ask those of you who have actually built/drove P-port cars about the specificis of the port and what will best suit my application.

 

we were talking about this the other night. paul had the opinion that you should just duplicate the mazda port timing, theres an sae paper on the 787b, it gives you the port timing, and a picture. he's got a point, we know that port timing works, the 4 rotor runs just as good as a stock fc (really, starts right up hot or cold) so it works.



i'm thinking if you are experimenting, you would be better off smaller with the port, and if the ports smaller, you can move it up a tad, and minimise the overlap, which should make it more streetable, but you loose port size, and overall power.



paul again says the intake has to be bigger than the exhaust, because the exhaust is supersonic, and the intake is not.



i say you can make the intake port more oval, like the exhaust port, and get back some area but keep the duration smaller.



mazda casts their own housings, so they made the exhaust port a little smaller.....



also if its a 3 rotor, its going to be more forgiving about this because you have more power strokes, and more rotating mass....

 

Thanks for the reply. Id love to have the funds/time to be able to experiment with alot of different size/shape, and port placements, but unfortunately I dont. I need to do this once, and do it right.. which in something like this where there isnt a whole lot of information to pull from, its a bit hard to be confident on the outcome.

 

i talked to the speedsource guys at seven stock and another experienced engine builder and they both said that the port timing acutally wont effect the performance to any real noticable degree. small changes in port timing that is, because of course large changes will effect the performance. so just get it as close as you can and dont worry about it all that much.



and as far as port shaping and directions, i think its pretty minimal again. it seems to me that Pports are pretty apathetic as far as port shape/size goes. to a small degree once again. just follow the general guide lines and dont worry to much about 5mm differences.



i think this is all because the ports are so large compared to normal rotaries and piston engines and open so fast compared to normal piston/rotary engines, that the small changes will not have that much of an effect.



but dont get me wrong 5mm changes will increase or decrease performance just not as much as you might think. we are talkin about 5hp up or down, not much.



you are going to get the most gain designing a correct intake and exhaust.

 

Do you happen to know the SAE paper number with the 787b port timing and picture?

 

http://www.rotaryeng.net/Lemans-roto...ns-overlay.jpg



more info on that picture can be found here:

http://www.mazdamaniac.com/ (click on the carboard box by the title 'Download Library' - then Publications and SAE Papers - then LeMan's 4Rotor)



and you might find this helpful as well:

http://www.rotaryeng.net/intake.html