Smooth Operator: Intake Manifold Fabrication

Smooth Operator: Intake Manifold Fabrication

Today, we’ll be taking a look at some more custom motorcycle fabrication taking place at Fluid MotorUnion HQ in Plainfield, IL.

The bike, which is a turbocharged Suzuki, is a friend of the shop’s, and he’s asked us to do a few jobs to help him out on the track this year. The biggest job at the moment involves a total retooling of the intake manifold. His previous version was little more than a tube connected to a box, which featured plenty of sharp angles that cuts down on the intake charge’s flow. In order to remedy that, we set about creating a manifold that would provide a smooth path from the turbo to the throttle bodies, while still fitting underneath the gas tank with a little flex room to spare. We started with the base plate, which consists of a round aluminum floor to which we’ve welded the four velocity stacks that will feed the throttle bodies underneath. From there, we started cutting aluminum tubing to give us the general shape of the manifold.


By starting with aluminum tubing coming off each far end of the new plenum design, we were able to see just how wide and tall we needed to make the final plenum. You might be wondering how it all goes together from here, but don’t worry; as we keep moving through the pictures, it’ll make more and more sense. With the two tubes taped into place, we cut and shaped what would be the neck-down that connects to the turbo’s charge piping.


Once we had the general shape of the plenum put together with the aforementioned aluminum, we carved out the inside to accept a single piece of shaped aluminum that will comprise the majority of the top half of the plenum. Now it should start to look more like a proper plenum…


After cutting out our aluminum top piece, we formed it in roughly the shape we needed and test-fit it against the already-built edges.


Seeing as how we’d need to start making exact cuts from here on out, we settled on fitting the big middle piece to one side at a time. After more shaping and edging, we had the first side where we wanted it, so we tacked it into place and test-fit it on the bike.


Then we moved to the other half of the plenum. Just like the first side, we measured each piece of aluminum extensively in order to get the exact edges we needed for correct welding. Without this step, we’d have gaps and awkward angles that wouldn’t weld together nicely, and we’re not about to let that happen. Not in our shop. It’s much more beneficial to put the extra steps in the early stages, because the end result will be that much easier to make and to look at.


With the top half of the plenum in place, it’s time to start putting the bottom of the plenum together as well. We’ll be picking that up later in the week, but make sure to come back to Fluid MotorUnion’s website every day this week for more exciting original fabrication content that you won’t find anywhere else! Have a great start to your week, and we’ll see you tomorrow!

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