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Original Pulley Design

The original re-made pulley was the incorrect size. This page contains the original design

The Pulley

Before I can really start with locating the SC to the engine, I need to nail down what I'm going to do with the SC pulley. The stock pulley has a 3-5/8" diameter. According to the calculations on [[2000 Subaru Impreza 2.5RSC Build Part 1|Part 1]], this is too big. I need a 3.25" pulley to get the correct SC RPMs when driven with my stock crank pulley. So I contacted one of the many existing supercharger pulley designers on the internet. After a few emails back and forth, Smooth Flow Pulleys offered to take on the challenge of making a custom pulley to fit this particular SC.

I wanted a system that would allow me to change the pulley size with as little effort as possible. Nate at SmoothFlowPulleys has already designed a modular pulley system for the Chevy Cobalt, Ford Lightning and other factory SCd cars. I thought a variation of his design would not only be flexible, but also would keep the costs down since he already has existing pulleys to draw from. So, I thought about how this all might fit together, scribbled a drawing, and emailed it to Nate. Don't laugh, it's rough I know, but the idea is sound.

pulley design sketch

The idea was to use a custom hub, with the existing lineup of SmoothFlowPulleys, then add the needed spline plate to tie it all together. Not visible in the above drawing, but the spline plate will actually be held with 2 of 4 cap screws. The other 2 holding only the pulley to the hub. The idea here is that the spline plate can be removed without messing with the belt system. Now, I can eliminate boost from the car, with nothing more than an allen wrench. Nate thought it was very doable, and we were off. I mailed him the original pulley, spline plate, and bearing. Less than a week later, my new pulley setup was on it's way back to me.

All 3 pulley bits

Mounted without and with the spline plate

In hind sight, there is one thing I think should have been done different. The idea behind the separate hub and pulley, is that most SCs have the pulley press fitted to the lobe shaft. This makes it a royal pain to change pulleys. Well, the C230 SC is NOT pressed on. A pair of snap rings, and the pulley comes right off. With that in mind, I think a one piece pulley & hub assembly would have been a better idea. I have not yet talked to Nate about this. However, if I need to obtain a 2nd pulley in a different size, I'll see what he thinks about this. But, as an alternative, one of the guys at the local AutoX events is the owner/operator of a high quality machine shop. Sounds like he'll be more than up to the task of any pulley making I'll need. First, lets see what the pulley does for me.

Here are all the pulley photos