Hey guys,
I was wondering if it would be possible to cut off the plenum on an FC intake and have it fabbed up with sheet metal. Then, since i am going to have a haltech, fabbing on a GM 75mm TB, to help get rid on the small piping and the restrictive elbow. Has anyone tried this? What other factors should i take into consideration?
Thanks!

 

Many of the experimantal planes built with rotary engine powering them have custom intakes utilizing the stock lower intake with some piping grafted on to it. Its possible to do it but what will the outcome be like? Will the throttle responce be good/bad and what will the car idle like? Those custome intakes on the planes are made to work at constant rpm and are tuned to work optimally at that rpm. We can't do that with our cars so we(mazda engineers) have to compromise. Just something to think about.

To answer your question I think its possible but do lots of research on it.

 

Well, as long as the new sheetmetal plenum is made to the same dimensions as the old plenum, what would change? All that would be different would be the throttle body size and possibly location. Anyone else know anything about this?

 

double post

 

If your going to fab the new plenum just like the stock whats the difference? Why not just make a adapter that bolts the GM throtle body you want to the stock plenum?

Later,
Stephen

 

This is ASE_Joe from a remote location:

As far as just putting the GM TB on the stock plenum, I am trying to relocate it so as to allow a larger inlet pipe from my FMIC to the TB without the use of the stoopid restrictive FC elbow. With a sheet metal plenum, I would angle the TB more upwards, so as to allow this to happen.

I was just wondering if any one on here, besides myself, sees the benefit in doing something like this. I would love to use a 13B-RE intake manifold, but cannot find/afford one

 

the plenums are split internally, the throttle plates open into different sections of the intake. besides i think if you add all 3 together i think they are bigger than the gm one. if you want big gains you may want to find a 48ida weber intake and get some 48ida throttle bodies
geneberg makes them for the vw guys.

mike

 

If the stock elbow on the throttle body is the problem then get the elbow from the 6-port NA's! They have a 3.5" opening and I always use them on any TII build-up!

crispeed
87 Rx-7 TII
9.204@150.47mph
2600lbs
un-tubbed

 

Would the na elbow not just point the intake at the firewall/booster area when used on the TII intake since the TII intake points the opposite way of the na intake? then you need more bends to straighten it out?
Whats needed is someone to make a an elbow like the greddy FD elbow for the FC..Max

 

Correction...
Crispeed, I put an old na elbow I had on my TII just to see.. The TB is flipped on the TII as compared to the NA, however the outlet runs right smack into the oil filler neck, are you not using an oil filler neck on your motors?
Max

 

I have also tried using the NA elbow on the TII throttle body and it hits the oil filler neck. I would like to make this work so I am also curious as to how you do it.

 

This is ASE_Joe:
I would like to know whats going on with this also. Do you mill the outside diameter of both down a hair? I was thinking if shortening the neck, and tapping it for the cap, but not sure where i would get that tap. I have some other ideas in mind for this interference problem, but just want to know what you do first.
thanks for the info, chrispeed!

 

Turn the oil filler tube 90 degrees. I am going to do this on my car. Here is my friends car that used that elbow a few years back:

 

Thanks for the pic Felix, I was thinking about doing that.
I have decided to skip the n/a elbow, I now have the ability to weld aluminum so I am going to make a custom elbow sorta like the one for the FD...Max

 

When I put the FD upper intake manifold, TB, and Greddy elbow on my TII motor the filler neck was in the elbow's way. twisting it wouldn't help. So I just cut a few inches off of the tube and welded the remaining parts back together.

 

Thanks Felix.