Project Miatabusa Part 4.3 – The Intake Manifold

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So, making new horns is as simple as slipping some carbon tube over the silicone, painting on the resin…

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and rolling on the carbon compression tube. You have to stroke it a bit to get out the wrinkles…

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After a brief refractory period, a respectable carbon fiber air horn is born.

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Now, time to make a plenum mold from a stack of Home Depot styrofoam…

(Notice how the second generation design will eliminate the shrouding probelm by making the short horns start at the plenum wall.)

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After gluing the foam sheets together with epoxy, a rasor saw makes quick work of the foam.

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According to our rough measurements, the new plenum's volume is pretty much exactly the same as the factory Hayabusa's. That was actually on purpose.

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The plenum shape is intentonally designed with no two parallel walls. Parallel walls can sometimes cause unexpected resonances that could potentially cause inconsistent air/fuel ratios. Better safe than shopping for another Hayabusa engine…

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Ok, it was close, but the plenum still didn't get along with the hood. The side facing the engine had to be shaved down at an angle to tilt the bulbous end down a bit. Now, where are we gonna find a sanding block big enough for that? 

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Success! With the hood closed and latched, the new plenum just squeezes under the hood.

hayabusa miata miatabusa throttle body hose

Now, time to make it hollow… Alex is taking the plenum back to his lair to turn this block of foam into another carbon fiber masterpiece, but first, he needs a model of the throttle bodies so he molds the air horns into the right position. Our intake manifold buck was whipped up from four 2″ PVC pipe caps and an old chunk of IKEA furniture. Now alex can make a plenum mold from the foam block, clamp the air horns to the IKEA buck for alignment, and bond the horns into the plenum. 

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All the Miatabusa you can handle:

  

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