i am going to recieve a newly rebuilt engine soon, and ill be running it with a standalone (haltech, unless i run into a microtech cheaper). i want to make my own intake manifold, which i have various designs for (any pointers or threads would help), but i was wondeirng what the best route would be for the throttle body? should i make it use the stock TB, or is there a relatively cheap aftermarket one, or one off another car that would work. ill be using stock turbo with all bolt ons and streetported, but am eventually gonna get a big turbo and go for around 400rwhp. (within a year).

sparknotes: I want to build my own manifold upper and lower, any pointers would be nice, or threads, and which direction i should go for a TB.

 

Heres the one I built, not much, but it took quite a bit more work than I was expecting. Its completed and on the car now, maybe I'll post some finished pics after I get it tuned this weekend.


https://www.rx7club.com/rotary-car-performance-77/few-pics-my-almost-complete-sheet-metal-intake-manifold-559817/

 

I made one too...

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/latest-pics-status-my-turbo-na-bridgeport-project-project-tina-498432/

 

wow, i dont know how i missed that thread, but NICE!

 

I must ask.. that both intakes has this huge box thing.. infront of the throttle body.. Now Why is that?.. doesnt that create less of a direct flow with a lil bit of back flow?..

 

The plenum is used to create "surge space". When the throttle snaps open, the engine wants to suck a huge amount of air so the plenum provides that air until enough air begins flowing through the throttle body.

It's a greatly simplified explanation, but basically accurate.

Another reason for the plenum is that if you can tune the length of your intake runners and plenum volume, you can use the pulses created by the closing of ports to bounce a pressure wave off the opposite side of the plenum so that it forces more air down the intake when the port opens...natural supercharging. All the NA Mazda intakes since '85 have used this effect.

 

I've now got free access to a foundry here that is owned by a club I'm in. One day I'm going to work on making molds for a cast manifold. Of course I have many plans that I never get around to so who knows when I'll get the time to do it.

 

Thanks for the explanation Aaron.. So now the question is what's the best shape of it and volume of air that is conjusted into the chamber (plenum)..


EDIT: i ask that question cuz i noticed that you went with the cylinder style while the first guy with a link went with a triangular pryzim style..

 

how have these intakes worked out for you guys? what did u make a fuel rail out of/what did u use?

 

I don't think there is necessarily a "best shape" for the plenum. Plenums of all shapes and sizes seem to work equally well however if you have a very complex shape with lots of bends and such you are going to create some very weird air currents. In theory you might be able to take advantage of some of those but most of us don't have a rapid prototyping machine and a flowbench to figure it all out...

Plenum volume is generally around 70% of engine displacement, but of course can vary based on the VE and characteristics of your particular engine.

I just started my car last weekend but so far I have to say I'm impressed. Throttle is not at all twitchy and throttle response is the best I've seen in a non peripheral port engine.

My fuel "rail" is just abit of braided stainless hose with AN fittings that run between the injectors. As the pictures show in this thread there are just two T fittings that supply fuel to the injectors. Oh, and you can see and hear the engine run in this thread.