I'm just about to put togeather my rebuilt S4 turbo engine, i have given the intake ports a mild open up and was woundering if i should open up the exhaust ports or not. I'm aiming for around 350RWHP.

 

welcome ...

it makes little sense to port the intakes and not port the exhausts. it's pretty easy to find templates out there for whichever exhaust you need for your goals, so start looking around. it may also be helpful to look up streetporting so it will all come together, instead of just taking my word for it.

good luck ...

 

In a rotary should it not be almost equal, take as much out on both the intake and exhaust.

 

Thanks for the advice diabolical im just a bit unsure on the exhuast side, you seem to see alot of info and pics on intake port but not on exhaust. I'm not sure weather im beter to raise the port up take it down or what?

 

I have heard that exhaust port area should be 70% of intake as a rule of thumb for NA. I have seen many turboed piston engines that use a slightly larger exhaust valve than thier NA version. With that in mind, I say get to grindin. I used a RB street port template on my 86-NA

^practice housing^
If you just did a little on the intake you might want to be a little more conservative than this with exhaust porting.

 

Did you remove the exhaust sleve from the rotor housing when you did your ports?

 

on a turbo motor i would go down a little but not up.

 

I have a 86 NA so yes I removed the sleeve to work on it.
Torched/ground out the NA diffuser
Welded the air holes shut
Welded/ground the sleeve to match the port in the housing as tight as possible
more on that here:
https://www.rx7club.com/rotary-car-performance-77/pics-rb-exhaust-street-port-6-port-478319/

Once that was done I re-installed the sleeves to do the porting.
Since you are already working with a turbo motor you don't have to worry about pulling the sleeves to remove that nasty diffuser in the sleeve.

Most of the exhust porting was done to the port in the housing and then just blended back into the sleeve. The wall of the sleeve is not very thick where it meets the port in the housing. I laid a weld bead on the sleeve to build that area up a little so I could port it out a little more. This whole removing/welding/grinding of the sleeve is a pretty tricky task but since I had it out and had the tools I went ahead and did it.

Edit: just found this article i had bookmarked... That should answer a lot of questions.
http://rx-sevenandahalf.com/misc/por...PR-article.pdf

 

Thanks a lot for the help guys

 

You don't need anything mega-fantastic large as far as the exhaust port goes. It doesn't need to be able to pass pineapples out of it to work well.

Have a peek at this for an example: http://bdc.cyberosity.com/v/Porting/JasonKennedy/

B

 

Thanks alot, thats a very helpful link, lots of great pics, looks like you guy do some nice work!

 

Small exhaust port of cosmo 13b-re