Smooth Criminal

Smooth Criminal

Today, we’ll be returning to the much-improved intake plenum we’re constructing for a friend’s turbocharged Suzuki drag bike.

When we finished up the last post about this manifold, we were prepping the other side of the plenum’s upper middle section to connect the whole top half together as a single piece. After some elbow grease, metal forming and tacking, we had the whole top half of the plenum together, in the shape we wanted. We laid the gas tank over it in the correct position, and it fit like a glove.


With the top half where we want it, it’s time to address the bottom half of the plenum. It’s still in a bit of a state, with remnants of our fabrication methods (mainly some sharp edges and protrusions) still hanging out. Therefore, it’s time to grind everything down to the shape we need before we cut more pieces of aluminum to fit.


Then, as you might guess, we cut out the pieces in the shapes we needed, and taped everything together for a rough fitment check. Once the fitment of the main underside pieces were in place, we tacked them in, as well.


We now have a more-or-less complete plenum body. That leaves us with two vital pieces left to attach — the tube that will connect the charge piping to the plenum itself, and the connection between the velocity stack plate and the plenum’s body. We started with the latter, once again grinding down the shape we needed, then tacking the velocity stack plate in place to seal up the bottom side of the plenum for good.


After that, we fit the tacked plenum back onto the bike and measured the angle of pipe we’d need to connect the charge piping to the plenum. After cutting out the correct angle, we tacked it in place. That’s the final tack necessary for the construction of the plenum.


With the tacks holding nicely, we returned once more to the bike to test out fitment, and then it was back to the welding table to work our magic.


Once it was allowed to cool, we reattached it to the bike once more and lowered the gas tank to make sure everything was still fitting nicely, as the heat generated from lots of welding can cause the aluminum to move slightly. And, as we’d guessed, everything fit together perfectly! Now we have a completed aluminum intake plenum, with more than enough volume and smooth angles to satisfy a proper operation under boost. It will flow much more smoothly than the previous setup, which again was little more than a rounded square box with four runners and some 90-degree bends.


With the plenum completed, we then moved to the task of creating the charge piping that will send the compressed air from the turbocharger to the plenum itself. There isn’t much wiggle room allowed, so we snaked the pipe as close to the body as we could, and tacked everything together once we found a shape that would have more than ample room behind the bike’s soon-to-be-installed single-piece front fairing.


We still have plenty more work to do on the turbocharged Suzuki drag bike, so stick around our website in the coming days for even more motorcycle content! Until then, have a great day!

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