Impreza 2.5RS + Eaton Supercharger = Fun

It have been a few years since I have been looking at getting more horsepower out of my Impreza 2.5RS MY00.  I knew from the start that the engine could not handle tons of HP, at least not without some modifications. Two solutions were possible, keep the engine internal parts as is or use stronger parts.

The stock 2.5RS engine block is open deck so to keep it reliable under boost for a daily driven car it's better to use a maximum of 5psi of boost.  Many turbo kits made for the 2.5RS go to about that amount of boost with some minimal engine management.

When you open up the hood of your Impreza you will notice rapidly that free space is minimal.  There are not a lot of options as to where to install a supercharger (a root type that is).  The main problem with the Eaton root type supercharger is that they are a bit big.  Two models are possible in my opinion for the Impreza: the M45 or the M62.  For low boost, the M45 should be enough to provide around 5psi.  If you need to go higher or want to install this on a WRX or STI (hey why not!!) then the M62 might be better.  The M90 is quite big and long, so unless you can find one with a short snout this is almost out of the question...I say 'almost' because I am sure with some tweaking there would be a way of fitting it :D

I came upon a site a few years ago about building a bracket for a Eaton M62 supercharger (M62 Impreza Bracket diagrams). This gave me the idea to try and do it myself following the plans provided.  Unfortunately some measurements were missing which made it a bit more difficult to build.  It turned out a bit different but worked just as good.  Another thing that forced me to customize the bracket is that I did not have the exact same M62 supercharger.  The picture below is an example of the unit I purchased off Ebay.  These are quite common but the condition it is in will vary greatly like their price too.  A great looking supercharger like the one in the picture could easily go for about 300$US or more.  You can get some for half the price but be prepared to spend some time doing some basic rebuilding.

In my case the supercharger was in good condition but not perfect.  I disassembled it so I could clean it and verify that there was no hidden damage.  It turned out the rotor was good but the coating on it was starting peel off.  In my next message I will discuss the reconditioning I did on the supercharger to ensure I could safely attach it to my so loved Impreza.

Note:

Want to know when the kit looks like installed.  You can find it here.