S13 SR20 idle air flow path

[mr.nismo.]

Hey everyone!

So I always thought it was weird that the OEM intake path was 3/4" ID hose to the valve, but pretty much every A/M hot pipe was 5/8. I figured it was since the the opening into the lower plenum is only 5/8. My thing is why the 3/4 all way up to the plenum, then reduce it? Looking at the casting plug, I wonder if it was more cost effective to do 5/8 (since mass manufacturing needs to just be "good enough") or if there was engineering behind it. Im toying around with opening up the original hole, or adding another directly under where the iacv sits. Im more leaning towards the second hole as to provide cyl. 3/4 with a more direct path of air. I also was curious if the Greddy manifold is like this? Ive never had my hands on one, and I couldn't find pics of inside the iacv chamber. It almost looks like its not just dumped straight into the plenum. Either or, I wanted some opinions on opening up another flow path so the full 3/4 ID of flow can be used. And also if anyone that has a Greddy Mani can chime in. Looking forward to the discussion!


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