mazdaspeed7

Im basing this, as well as my previous recommendations on theory and research I have done, not on actual experience(yet). I cant really say absolute or specifics about what exactly a port will do, but I can give you an idea how the different ports compare to each other. That being said, the first port would be my choice.



Exhaust velocity is especially important to a turbo car, because low velocity will lead to a laggy turbo. The exhaust port you already have appears relatively large, and if you go too small on the intake port, you run the risk of making the engine very dependent on low backpressure to maximize its performance. And the fact that you will have a turbo pretty much means you will have at least a moderate amount of backpressure. There is a ratio of exhaust area to intake area thats optimal for flow. Lots and lots of research has gone into small block V8's, and they are all pretty close to a 1.59:1(exhaust area: intake area). It may or may not be different with rotaries, and side ports throw a whole extra set of variables in there. PP's would be good for determining the ideal ratio, but there are so few variations out there.



I can say that my n/a with a big streetported intake and race ported exhaust was very strong, but it was terribly sensitive to backpressure. By the time I got it running right, it was so loud it was almost hard to drive for any amount of time.



With a large exhaust port, you will run into diminishing returns from making the intake port smaller. Exactly where that point is will have to be a matter of experience and experimentation, but if you keep the ratio reasonable, you should have nothing to worry about. Less than perfect usually works well enough that if you didnt know true perfection, you wouldn't know that its not.

LimitedSlip7

Well, I got the holes cut, still working on the inserts. Ports will be ~40x50mm after the inserts are in. Should have at least one completed housing done this weekend.





Heres a teaser:

trydis7

They look great! fitting the non-round insert should be time consuming

How are you going to fit / secure them?



Regarding the port size / shape. Some of the Mazda SAE papers give clues.

And there are lots of pictures around of the various Mazda PPort intake shapes but few published shapes / dyno results.

One of the better references is SAE900032 - with rpm and volumetric efficiency %.

Your timing looks roughly similar to some of the SAE papers. What is the IO/IC?

Expect lower boost numbers due to the better PPort flow (for the same power). These should eat a lot of air

C. Ludwig

Looks great man!

LimitedSlip7

I almost have one of them done. Place sent me the wrong v-band flange the second time around, so I couldn't start on the second one. Still have to fill the jacket in with Devcon and I think I'll put a larger radius on the closing edge...



Piks! They kind of suck though, I'll try to get better ones later.

mazdaspeed7

That looks really good! I cant wait to see it all go together.

BLUE TII

How wide can I make the port and still reliably support the apex seal? This would be with 2 piece RA seals.



Have you considered ANY other seals?



I have used the 3mm and 2mm RA seals with 50:1 premix on top of maxed out stock OMP and they still wear the chrome off the housings very fast. The higher rpms, egts and race conditions this motor will see will really exasperate the high wear.



After all the work put into the housings I couldn't imagine subjecting them to RA seals.

LimitedSlip7

Well, yes and no.



Problem is I'm a broke *** college student. I used RA seals before and they seemed to work well(although they did wear the housings rapidly, but maintained compression), so I was thinking about using them again. I would love to spring for a set of NRS ceramics or something, but I just cannot afford them at this time. I might be able to spend AT MOST $450-500 on a set of seals, so I may go with OEM.

mazdaspeed7

Atkins seals are nice to rotor housings, they are a bit softer than RA for sure, and maybe even OEM. You will need a little extra clearance with them as they expand more than OEM at temperature. Ito has a thread with the specifics on them. I used them on a big SP 6 port engine I was pushing to 9600 rpm and the rotor housings looked brand new after 20k miles.



Personally, I would avoid RA seals for a high rpm engine. The wear increases dramatically at higher rpm, and these seals have been all but proven to wear the housings out quicker than OEM seals. I was perfectly happy with the atkins seals, just pay careful attention to clearances. OEM seals, Im sure are good at high rpm, but I have no personal experience there.

LimitedSlip7

Sorry to link to the "other forum" but I really didn't want to spend all the time copying and pasting it all over here. Check it out if you are interested.



Peripheral Port Build Thread