hi

Scalliwag , very nice work indeed , what happen to post #69 pictures

cya

 

This is a stupid question, but once you have decided upon the port timing you want, how do you accurately translate it into dimensions on the rotor housing?

 

Degree wheel would be the best way.

 

wow great thread, i'm glad to see some of the experienced guys getting involved in this thread...

Jay7...

 

Is there any way to accurately predict the powerband based on port timing? I'm attempting to design a peripheral port for a boosted application that will only be revving to 8500, but there is very little information on RX7club and NoPistons about the subject.

I might just wing it based on what I personally think might work and hope for the best...

 

Depends on what you mean by "accurate". You can copy what other people have done and fudge here and there. Actual accurate prediction involves computer modeling.

 

I suppose just a general idea, like say X port timing should make peak power around 7-8k with a very good midrange.

The problem with copying is that very few people are actually willing to share detailed information about their setup and the results they achieved.

 

Pics to be posted after I take them, but finally buckled down and cut the S5 housings I have sitting around for PPort. Timing's about median between old style and new style MFR housings (that is to say, the numbers in that paper I keep bringing up) and looking at 1 3/4" ID on the tube. Which, yeah, may be on the smallish side compared to what some are doing, but I'm figuring on something roadrace/street oriented.

I'm figuring of doing a lot of dyno mule work on the intake/exhaust, as I'm fairly sure that's where gains are... hell, pulling my head out of my *** and looking again, on ye Maz paper, runner length and diameter played a lot larger part in shaping the powerband than timing. But hey, who knows.

Incidentally, I got sick of bottoming out the hole saw, so just chucked up a 1.5" end mill I've got sitting around and used that to make more room. Rough cut the hole with the holesaw, then used a boring bar to finish the hole to diameter, and open up the rest of the housing to tube OD. Made a nice press fit.

 

Did a bit of layout work to see how the port I was thinking of using would compare to the MFR port and to find out what the port timing would be.

The port I designed has almost the same port area as the MFR, would close at the same time as the MFR port, but would open 15 degrees later. I have been advised to increase the port radius's and open it earlier.

Any predictions for the performance of this port and advice to improve upon it to match my goals? Any thoughts on entry runner angle?



Finding port timing with degree wheel:





MFR port:





Square port I'm thinking about using:

 

Looks good. What is the characteristics of the square port vs the round port?

 

I have read Mazda used square port for qualifying as it flows more but must be kept at high rpm to keep velocity up.

Round port for racing as it has good overall power due to same timing but more velocity in lower rpms.

Turbo applications may be able to use a big square port and keep the rpms low enough for race reliability.

 

I am going to make some p-port housing for my 12a. It looks like the norm for 13b outer diameter is 2". What is a good diameter for the 12a since the housings are 10mm thinner?

 

This thread is friggen insane.



You guys are damn brave haha.



I would like to see a PP with custom irons, becuase really you dont need those thick *** irons if you have a PP intake.



=Ben

 

hmm. . . that's an interesting idea that I hadn't yet considered. Anyone know if anybody has done anything like apexFD just mentioned. . . thinner intermediate(s) and a shorter e-shaft.

 

Well- of course, you still have to cool the surface of the sidehousings somehow so there may be a limit on how thin you can go.

I believe the NSU P-port production engines cooled the housings with radial flow instead of Mazda's axial flow, so that is one possiblility.

It might help to use aluminum for its superior heat transfer with a sprayed on wear surface like early Mazda 10A production engines and its new 16X concept.

 

what do you guys think of this. i found the pic on the net. not this is back yard p porting.
http://www.geocities.com/izzmus/shotgun/shotgun.htm

 

It's probably already been posted in this thread, but I don't have the patience to traul through it, but where can I buy factory peripheral port housings for a 13B?

It's for an FD3S motor but I guess it won't make a difference if I get second gen peripheral housings?

 

that intake is an abomination. . .

 

thats the frist thing i thought of when i saw it. how about the door screen used as a oil baffle.

 

Wasn't that Peejay's setup? It belongs to someone on the forum.

 

iam not bashing it i just thought the screen was funny. wish he updated the web page and talked about how it went. the last thing on his page about it was ready to install.

 

http://www.youtube.com/watch?v=FR9hHHJKJA0

Friday, as it happens:





Goal is the next rallycross on the 20th.

 

Did it start? Howz it run? That's a big squre port you've got there.

 

how did it go

 

http://www.youtube.com/watch?v=Tr7vU3cbH6E

I should explain the screen. I had two reasons for it: first and most practical, I removed the screen on the pickup tube and bellmouthed it, and I am somewhat paranoid about random junk getting sucked into it and mangling the oil pump, so I figured the screen would protect against that sort of thing. Second, I was hoping that any air bubbles would get broken up and/or stay above screen level, to help ensure that the oil the pickup saw was "solid".

It was a lot of fussing around. This time, I just used an unmodified pickup. I'm not winging the engine up real high, the stock oiling system is good enough.