Porting and Polishing M62's


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These procedures are specifically written by me for the M62, however much of the information may apply to the M90 as well.  I have done this on both the 92/93 Gen2 and the 94/95 Gen3 superchargers, as well as a handful of Gen3 and GenV M90's (examples shown near the bottom of the page for the M90).

 

Porting and Polishing these superchargers should be done very carefully.  The general idea is for smoother inlet and outlet flow, and decreased inlet/outlet temperatures.  Hot air is bad for performance, but is a natural by-product of compressing air.  With a little attention to detail, you can help things out a bit.  Rough or sharp edges tend to get hot quicker as compressed air is blown over them (friction is what causes this as the air passes over these surfaces).  Simply smoothing off the cast surfaces and rounding sharp corners can go a long way.  I don't suggest changing the sizes of the inlet or outlet in any way, nor the two small slits to either side of the outlet.  These slits are for sound, and actually make the supercharger's operation quieter (the reduce the effect of the pulses as each rotor releases it's compressed charge to the outlet).

The first supercharger I ported and polished was a Gen2 from a 93 SSEi.  Many of the features I created in the outlet were already rough cast into the Gen3 by Eaton when manufactured.  It gave me a good feeling to see I'd done what was incorporated into the following generation.

Tools and Equipment

Don't laugh.  I used a dremel tool, but now use air tools as my skills and confidence have improved.  I chose the dremel tool for a reason early in my porting experiments, as it doesn't remove a lot of material at once like a die grinder would.  You don't want to make a mistake.  I used a combination of carbide 'twist' bits and sanders, finishing up with a polishing tip.  For the inlet, I used a flap sander to smooth out the rough casting texture.  I also strongly suggest a flex shaft, particularly for the inlet.

Let's get started!

Look at the rough sharp edges on the outlet of the Gen2 92/93 Supercharger in these pictures:

      

These rough edges and sharp casting release messes must be removed without disturbing the inner surface of the rotor casing.

Start working on it.  I'm not going to give specific instructions, as these pics should explain it very well:

      

      

      

      

Now that we're done with the mess, sit back with a beer and enjoy your work:

      

      

From this point, you can polish the living snot out of it with the Dremel tool.

 

These pictures are of the Gen3 94/95 Eaton M62.  If you look closely, you'll see that some edges were already rounded off, but still left rough after casting:

      

      

Time to start cutting again:

     

      

And the finished outlet of the Gen3 Supercharger:

      

      

      

And the before and after pics of the inlet.  This is where the flap sander was used.  It's not really necessary to increase the diameter of the inlet, as the throttle plate is the limiting factor, but smoothing out the rough casting to ease the airflow can go a long way:

      

 

Updates to show details of the M90

On the M90, two of the threaded bosses cast into the outlet actually protrude partly into the outlet area, restricting a small amount of flow.  These can be cut out, but I strongly suggest that if you do, you either cut out only HALF of the protrusion on the M90 Gen3, or cut it all out and Heli-Coil the remaining threads for strength.  Heli-Coiling the M90 GenV is not necessary (and you can cut them out completely), as the alloy used in that housing is stronger:

Gen3 M90 bosses cut out.  I didn't cut them out completely, I'll finish and smooth this with the dremel or air tools as I finish re-shaping and polishing the outlet, then heli-coil the remaining threads.

 

Examples of a finished M90 GenV outlet:

 

On the Gen3 and GenV M90, smoothing and lightly polishing the inlet is done as described above for the M62.  In this example, I blocked the EGR port at the request of the owner.  This should be done in all cases where an intercooler is planned.  If no intercooler is planned, keeping the EGR is beneficial not only for emissions, but for performance as well.  It helps to reduce knock, and actually REDUCES combustion temperatures.  To fill it, I roughen then inner surface of the EGR passage with a coarse dremel or carbide die-grinder, then use tape across the INSIDE surface of the inlet, flip the supercharger over, and fill the hole with JB Weld (not rapid cure).  After it cures, I re-shape the inlet to blend it:

Be aware that the alloy used in the M90 GenV housing is different than the M62 models and the M90 Gen3.  It's tougher to work with, and requires patience to get a good finish.  This is true on the inlet and outlet.

 

 


How they work          diagnosing problems          porting and polishing          rebuilding nosedrives          Swaps and upgrades          Adding a boost gauge         

replacing needle bearings     adding a nosedrive drain          supercharger oil change          pulley size suggestions          links, references, and sources


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