Renewing a topic that wandered a bit......I know Foghorn'* pics don't work any more, but It'* time to add a bit to it. A word of warning, this modification is NOT for the faint of heart, and you can screw up your Supercharger very easily if you aren't VERY careful.
Yesterday, while extracting my needle bearings, I noticed alot of casting flaws around my outlet port. Taking Foghorn'* lead, I set out to clean it up to improve efficiency, airflow, and decrease outlet temps (sharp edges in the airflow path show up hot in thermal analysis). Not that I did NOT modify the actual size of the outlet port. This is very important.
Note the restriction in the above pic. This is the underside, nosedrive end.
Another angle of the same flaw. The inside edges near the rotors (in the compressor chamber) don't have this problem, but the air still must turn 90° to exit the outlet port.
Removing casting flaws on the inside edge of the outlet. Notice how it actually restricted the opening. They didn't only extend DOWN, but also into the opening. It'* easy to see here while it'* being removed.
Working my way from left to right, getting close to the worst part on the right side of the pic.
Still working on the outlet restrictions, the worst part is very apparent here at the bottom of the pic. White rag under the SC to show the flaw.
Just about done with the inside edges, ready to tackle the bad stuff.
Starting work on the worst of it. ALOT of material was removed here. This was obviously not intended in the design, as the contour of the outlet port was quite well defined, despite the protrusion of the flaw.
Nearing completion. This is after chamfering the outlet, but before fine sanding.
Another angle of the same stage of finishing. Keep in mind that I'm working on the inside and outside simultaneously. The inside is VERY delicate and restricted for working space. The rotors spin at insane speeds, so you don't want to induce a single burr or high spot.
Inside view of the outlet port before finishing.
Ignore the funny stains on the inside of the blower. Those are solvent marks from the ultrasonic cleaner, and wipe right off with Acetone.
Another warning........this is delicate work, and easy to screw up. I'm expecting slightly increased efficiency (flow), and slighltly lower outlet temps. If this buys me a couple horsepower, it was worth the 3 hours I spent on it, as I already had it apart anyway. Much of this is impossible to characterize given the resources I have available, but it'* certain to be at least a small improvement.