Hi
Im about to go P-port on the racecar and have a few Q´s

* ??
On the MFR Intake manifold the IDA flange bores is 51 mm and gets smaller at the portflanges, 43mm, now im thinking with the old P-port setup the portbore is 50mm at the flanges Pic.
Would this have to do with flow dynamics or was it just plain wrong to do it that way?

* Intake
Im about to convert S4 N/A housings to P-port and would like to use the MFR intake manifold. Having a round port with the same bore all the way through...
Should i go for the 43mm like the MFR manifold bore or 51mm like my Weber IDA and make another manifold?

* Excentric-shaft
Are all 13B shafts the same, i mean weightwise.
Current eshaft is fucked and we need a new one, the thing is that we do have clearenced/machined/balanced rotorsPic. and matching counterweights, but the shaft they were on is no good. Can we just get any 13B shaft or is there also difference in journal diameters? Would an Rx-8 shaft work in the older 13B motors?

* 3-window bearing
I have ordered 3 window bearing for the rear, does this require drilling two more oilholes in the stationary gear? The P-port motor that the car came with didnt have three oilholes and I havent been able to find any specs on it.

Thanks in advance.
-Kim

 

"Im about to convert S4 N/A housings to P-port and would like to use the MFR intake manifold."

If you are going to convert the rotor housings to PP, then why not use the Racing Beat Intake manifold part number 16490, price $170 US Dollars? Instead of trying to weld up and machine out a flange to match the factory PP manifold in your non-factory PP rotor housings, it will be much cheaper to press a 51mm tube into the housings and then attach the Racing Beat intake manifold that was designed just for home made PP housings.

As far as I know, the RX-7 13B shafts all have the same journal diameters. I am ignorant about RX-8 motor details.

Use the 20B rear stationary gears and bearings.

 

Thanks Speed.

I was just a little confused on how the 43mm MFR intake was able to make the 298hp the old engine had??
The 43mm intake matched up to a 50mm port, thinking it was something to do with flow dynamics and stuff I know nothin´

My first plan was to use/fabricate the RB manifold. which im now back at.

Anyone with knowledge on the Rx-8 shafts!!!

 

http://www.rotaryaviation.com/renesis_engine.htm Scroll down all the way to the bottom of the page. Apparently the oil hole on the RX8 eccentric shaft is moved .150" forward so you would need to the RX8 front stationary gear to match. All other 13b eccentric shafts are the same.

 

Nice, thanks.

 

I have a set of MFR 12a housings for sale if any one is interested. They have about 5 races on them and are in good shape. these make about 10-20 hp more than the best of the hommade ones. good for 290-320 bolt together, 12a.

CJG