Hi everyone. Although this is my first post on this forum, I am not really new to RX7s or rotary engines. I own a 86 Sport which I am currently prepping as a track day/weekend warrior car. I am not planning on racing competitively, merely wanting a fun car to go all out in a safe environment. After building a couple streetport motors, Ive decided to give the Pport a try.



My goals:

I would like something in the ~250whp range

Idle <1500rpm

+20mpg on the highway

Not go deaf from driving on the streets



After spending several hours searching, I still havent gotten a clear answer about what size sleeve to use on the housing. This summer, I will have access to a machine shop, so equiptment shouldt really be a limitation. I would prefer a interference fit on the sleeve but have some questions about that. How do guys get the inside edge contoured (edge the rotor passes over) ? With a interference fit, is it really possible to do a test fit to scribe this onto the sleeve?



A bit off topic, but are there any guys still running the NA transmission with a PP motor? I have access to a fresh NA trans and would really like to keep it.



Thanks!



Alex

 

I think the real question is, where do you want your power band to be?



What length of intake runners do you want to run with this motor?



My housings are interference fit 0.001". The sleeve was stuffed in, without worry of the inside contour (chrome area), just a big chunk of aluminum sticking out. My housings were then sent elsewhere to have the inside section of the sleeve cut away and flushed up to the chrome (on a programmed machine). You could easily do that part yourself with a die grinder, but it's more time consuming. The machining work on my housings quoted up for any walk-in customer at 1100 bucks.

 

step one is to figure out what you want your powerband to look like. we know what the factory P port timing is, and where that powerband is, but if you want something milder, then the port gets smaller. smaller ports = milder engine, better idle, cruise etc etc



oh so, the port timing, gives you the port size, basically

 

The exhaust system will be key. It will be a balancing act, with power/economy/idle on one side and noise on the other. Low overlap engines are a lot more tolerant of a restrictive exhaust so you can make some "mistakes" and still work okay, peripheral and bridge engines are not.



If you can get over 20mpg now then there's no reason you shouldn't be able to with a peripheral port. Programmable fuel injection is assumed.

 

I would like to have peak power around 9k or so. I plan on having a set of S5 NA rotors lightened via CNC and get the entire assembly balanced to run up to 10k. As far as powerband, I want something I can still drive on the streets with out too much fuss. Im not sure what intake runner length to use. Ive read that the propper exhaust runner length is between 10"-12", correct? What exactly is the MFR housings power band like - not just peak power, but mid range too?



thanks,



Alex

 

I had planned on running 2" primary headers into 2.5" back. Is that too small? I wanted to keep velocity up without choking it off too much. As for being loud, I also planed on having a large presilencer for the street and welding V-bands so it can be quickly removed once at the track.



For engine management, I am considering Megasquirt. Ive done quite a bit of homework, and it seems to meet my needs (and budget friendly!)

 

2" primary should be fine, as thats prolly a little larger than the exhaust port outlet, but it should feed into at least a 3"

 

So a 2" merged into a 3" wouldnt kill velocity? Im not entirely sure whether more flow outweighs higher flow. Back to my original question about the PP sleeves, whats the common ID?

 

What I really meant to say was, Im not sure whether more flow outweighs higher VELOCITY. sorry for the confusion.

 

2.5 is prolly too much backpressure...



my 12a PP intake ports are 1 3/4", exhaust is 1 7/8", this is measured at the intake/exhaust flanges. mine are really old factory parts, so i'm expecting it to run like a factory PP, torque peak @8k....