wankel=awesome

So I'm gathering parts at the moment to build a semi PP 12a engine, and I'm actually curious about some of the details.

I have JDM 12At housings with filled in water jackets already where the normal coolant port to intake manifold would be, so they should easily modify for the 1" bore holes.

I also have 2 different intake/carb setups to run. One is a 48 IDA manifold that's been drilled, and an empi IDA w/42mm chokes. The other is a custom cut down RB manifold that's been drilled for semi PP, and has a 3.5" square bolt pattern for a nikki carb on top. The nikki is an experimental 26/31mm choke carb, so it's almost like no chokes at all in the main body.

​​​​​goal for the build is a strong NA base to turbocharge later, and I'm extremely in favor of running 2pc 3mm seals.

my question is which side ports to run with it. And where?

for 2 pc seals I need to be either half bridge or street port, but I'm unsure on which I'd want for the application.

I will be running this engine at least 1 year for DGRR NA, but I do plan on an intercooled low boost setup for it later on.

my thoughts on getting the most out of the engine NA would be half bridging it, but I'm torn on whether or not it will actually drive nicely.

for the IDA setup, bridging the secondary plate's would be ideal, but for the 4bbl version, the intake manifold is already sharing intake runners between the 1" semi ports, and secondary plates. The primary ports will be divorced, and running on primaries only.

Exhaust ports should be pretty large too. For the exhaust system in general I planned on trying to modify the long primary system (or build my own) to larger diameter pipe, with at least a 3" rear muffler.


I can't find any comparable builds, besides a guy that got 190 RWHP from a nikki 12a with a full 1.5" peripheral port... im curious if anyone has delved into combo porting (or simply full pp) for a 12a with the intent to turbocharge, and what sort of power it should make.

wankel=awesome

Shame I can't get any interest on this.

Siraniko

iTrader: (13)

my rx3 has a s5 t2 block wiht 91 N/A rotors half bridge semipp with single 2.5 exhaust. i have a 51 IDA with extended fuel bowl, msd fuel injection pump. i moved away from a full bridge semipp due to no low end

wankel=awesome

How does it drive with the open semi pp full time with the weber? Would you recommend half bridge or street port?

Siraniko

iTrader: (13)

i have no experience with SP semipp. i havent fully tuned it yet, still playing with different venturies and timing (gears still at 3.90). it is much better than driving a conventional full bridge. i can feel when the semi kicks around 3k rpm, same feel when the secondary venturies open up on a modified niiki carb kick.

wankel=awesome

Interesting.... so the semi p port isn't really fully in play until 3k RPM on your setup... That's nice to hear considering your intake manifold has no means of mechanically cutting them off. Maybe there's no need to?

Siraniko

iTrader: (13)

the manifold need to be cut with runners welded also so the semipp will get fuel. you will hear the sweet lope from the semi even idle

wankel=awesome

Right, both intakes I have are cut for the semi p ports. Both have 3/4" or 1" sleeves. Undecided on which I'll run.