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Old 05-12-2020, 03:25 AM   #1 (permalink)
JulianEdgar
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Join Date: Nov 2017
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Insight Gen 1: variable length intake manifold

I've always liked the idea of a variable length intake manifold on my Gen 1 Insight to improve torque off boost. (It's turbo'd and doesn't use IMA.)

The Australian Ford Falcon six cylinder has featured over the last few decades a really nice variable length intake, with the changeover effected by butterflies inside the manifold.

Generic pic of Falcon engine bay (inlet is the snail-like casting):



Lots of Falcons were sold, so the cost of the inlet is basically nothing - eg US$15 from a wrecker. Here's what it looks like inside. Note the butterflies that cause the air to pass through the longer runners (the snail). When open, the air takes a shortcut.



I sliced it up and bent some heavy wall aluminum tube that will connect to a manifold plate. Shown here with standard intake manifold in background. The bent tube is much longer than it will finally be. I have a TIG welder but I don't know if my skills will be up this one - might need someone else to do the welding.



My measurements indicate these runner lengths (approx):
  • Std Honda - 330mm
  • New intake manifold short - 350mm
  • New intake manifold long - 610mm

It's not a quick project, so don't expect results next week. Will be interesting to see if it makes an improvement - lots of unknowns like the impact of larger runner diameter, different plenum volume, etc, etc.

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Last edited by JulianEdgar; 05-12-2020 at 04:14 AM.. Reason: typo
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