The bracket prototype

When doing a custom supercharger fitting job there is always some starting point.  Of course I had to start with a prototype that worked but was not visually nice.  Some portions of the prototype bracket still need some fine tuning for excellent fitment and prevent cables/wires or pipes to rub against it.

Although this bracket was design for the MY00 Impreza 2.5RS, I intend to do another for the MY04 (if ever I can find the time).  It should be fairly similar but one major problem is that the intake manifold for the 2004 Impreza 2.5RS is made from some sort of plastic.  I believe this was done to increase thermal insulation hence keeping the intake cooler.   Since it is not made from aluminium, I am not expecting to be able to bolt easily the supercharger bracket onto it.  I will need to find bolts location (free or not) surrounding the manifold that I could use to hold the upper part of the supercharger bracket assembly.

Let's get back to the prototype I made for the MY00 2.5RS.   The most difficult part was to make the bracket such that it will flex to a minimum under the various engine load conditions.  I had to add some reinforcement at key locations to prevent this.  Any variation in belt tension could lead to slippage.  Belt splippage will make the boost erratic, and will shorten the life of the belt...not to mention terrible noise ;P

The bracket is made from steel, mainly because it doesn't cost a lot and is easy to find.  Aluminium would have been lighter but to obtain the same rigidity I would have needed to use specific type of aluminium.  The cost of aluminium is generally more that plain steel.  Another good point is that I have no equipment to weld aluminium and never welded aluminium (but I would love to learn how to).

I used pretty tough angled steel pieces to ensure that there would be no flexing. The supercharger is not as heavy as a M90 unit but the M62 is not that light either.

My kit is far from perfect and not totally to my taste.  As of now I do not have a way to adjust the tension of the belt driven by the S/C.   Another thing to note is that in order to driven the S/C I installed a pulley on top of the steering pump pulley.  As you can see on the pictures below this is not ideal but it is functional.  This is still a lot of room for improvement.

Minor supercharger tune-up

Getting started...

The first step is the empty the oil reservoir.  Simply unscrew the oil plug and pour the oil out.  If you want to have minimal residual oil, you will need to leave the supercharger inclined over a can for a little while.  The is not a lot of oil in the reservoir, it's about 90ml for the M45 and 100ml for the M62.

Next, unscrew all bolts holding the snout to the rotor housing.  When all bolts are removed you will note that the snout is still firmly clamped and won't come off that easily.  This is normal since a silicone gasket is acting as glue.  You will need to find a rubber or wooden stick and tap to snap it off.  Getting it off might be tricky.  The snout is 'glued' to a section on which the gears and rotors are installed.  If ever you want to pry between the surface make sure you do not damaged the mating surface.  First simply remove the snout portion and leave the gear section attached to the rotor housing.

(Pictures coming soon...)

Inspecting the snout

Verify the internal of the oil reservoir.  Is there any contaminant that could indicate the gear are damaged.  This should generally not be the case but perhaps a lack of oil could result in the gear failing.  If you don't see anything special you can clean the snout portion using brake cleaner.  Make sure you removed the coupler (black or green round shape thing attached to one of the gear or the snout inner shaft) before starting to spray brake cleaner.

(Pictures coming soon...)

Inspecting the gear

Next verify that the gear are in good condition.  Also you can make sure the coupler fits tight.  If the coupler is too loose consider replacing it with a new one.  You can find coupler for a fair price on Ebay but I'm sure a little search on Google will find many supplier and maybe even one near you.  I have diassembled two superchargers so far and in both cases the gears were in perfect conditions.  These supercharger are very tough and made to last for the life span of the car it is installed on.  Unless something bad happen like the supercharger swallowing sand, there is very little chance you will have damaged on the parts enclosed in the oil reservoir.

(Pictures coming soon...)

Rotors and housing

Probably the most important parts of the supercharger are the rotors and its housing.  Anything else that air entering the inlet of the supercharger will probably endup damaging the rotors and/or the housing.  Careful inspection on the rotor lobe is necessary.  You should look for dents or various marks.  You must make sure that the rotor are very smooth.  Usually there is a coating on the rotors.  Sometimes it starts to peel off, or some of it can have been damaged.  It the peeling is too extreme you might need to consider removing the coating.  I have read that it will affect how much boost the supercharger can provide.  Removing the coating can reduce by 1% the amount of boost, so if you were aiming at getting 10psi, you might end having 9psi instead, which is not that bad in my opinion.  At least you will be sure the coating will not endup in your intercooler, or even worst, in the combustion chamber.

Gasket remover can be used to remove the rotor coating.

Below you can see the rotor of my M62 unit.  Some peeling was starting so I decided to remove the coating entirely.  I simply used gadket remover, it works like a charm.  Spray it, wait around 3 or 4 minutes and it will peel off very easily.  Make you do a final cleaning pass with brake cleaner to ensure there is residual contaminant.

Rotor with the gasket remover applied and starting to react.

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No more nasty peeling coating... looks pretty nice.

A good portion of the coating removed.

Looks better than before and I can be sure no nasty coating will finish in my freshly rebuilt engine.

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.