Write-Up: S/C Port & Polish

All finished except for a little more polishing on the rotor plate edge.

First person with $1000 gets it shipped to their door


Some paint progress pics. The blower only has 10k miles one it...




It's hard to capture how smooth the surface really is. i went back about 4" and opened it up some. (78mm?)


Notice where the rotor edge is in relation to the outlet


Any suggestions on making the rotor slot look like chrome? what tools, compounds,etc?

Also any comments on the port and polish job? I've ordered a 77mm N* adapter and i guess i have to port the N* at some point too.

oh, and this was all done in 2 afternoons with hand tools...

Is it perfect? no. But it's way better than what any vendor sells IMO.

that looks very close to mine!!! the outlet and inlet..

did you fill the silencer ports or leave them like in the pic?

Matthew,
With everything i have read about the heat from welding distorting the chamber and ruining a good SC, I would leave it alone. Being Aluminum, it has a very good chance of distorting and protruding into the chamber. You will know when your rotors won't turn anymore.
Filling the ports will not provide any more output out of the SC only produce more whine.
It isn't worth the gamble in my opinion.
Finish your polishing, bolt on the N* and LQ4 and enjoy the additional HP and Tq

Thanks for the info.
I was after more whine...
I'll have the guy look at it and assess the risk. He is a master welder and trainer for our company. The parts at work are $9-12k each and one bad weld will cost $2000 to fix. These guys dont mess up very often, and he is the best of the best. All parts are checked for things like fisheyes, linear indications, etc. It's checked with fluorescent dye and 10X magnifiers and this guy has 98% pass rate.

With that said, the parts at work are turbine vanes, not superchargers.

Rick, didnt you have a gen V to install too?

Looks good Matt
any more pics of the inlet deeper in?

Nevermind about the pics - I didn't read the part where you said you went in about 4" - that was referring to the inlet finishing right?

yes i sanded back into the inlet about 4". its not perfectly polished all the was back due to the drill i had hitting the area i already polished, but it should flow very well.

Mr.Riviera wrote:

did you fill the silencer ports or leave them like in the pic?

mine came ported.. i didn't fill my silencers.

Mr.Riviera wrote:

Thanks for the info.
I was after more whine...
I'll have the guy look at it and assess the risk. He is a master welder and trainer for our company. The parts at work are $9-12k each and one bad weld will cost $2000 to fix. These guys dont mess up very often, and he is the best of the best. All parts are checked for things like fisheyes, linear indications, etc. It's checked with fluorescent dye and 10X magnifiers and this guy has 98% pass rate.

With that said, the parts at work are turbine vanes, not superchargers.

Just remember how tight the tolerances are in the bore of the SC and the tolerances between the rotors and the bore. If you distort that by the smallest amount, I'm talking ten's of thousands of an inch 0.0000, then you have ruined the outer case , unless there is somewhere that can line bore and hone it back to spec's. But I'll bet even Eaton will say too much work and it's cheaper to replace the unit.
I have not read about anybody offering a boring service and if they did it would be similar to boring a cylinder oversize by a known amount to accommodate a larger oversize piston / rotor.
Don't even gamble, saw one down at BillBoost's place that a so called expert thought he could do and turned it into one big paperweight.

You've done a good job with porting and polishing for extra flow and the GenV with a 4" hose to an FWI will make plenty of noise when you step on it. Leave at that while your ahead.

What kind of gains (HPandTQ) can be expected from a full port and polish job on an M90? Will it change the characteristics of entering into boost or the whine of the blower?

It can make an improvement, or it could result in decreased performance if you don't have the right plan. Porting the outlet is more science than art. Venders like ZZP and INTENSE have perfected their results using bench flow testing; very objective. Unless you're using a pattern to copy what has been proven to work, or you have your own bench testing equipment, you are really attempting art, which might be personally satisfying, but will probably not give any real gains.

I have an extra LIM and supercharger in good shape that I would sell if you want to work off the car. I bought these with the intent of porting and polishing, and matching the outlets, possibly modifying for IC, but I'm really happy with my engine's performance after the rebuild, so these parts are just sitting at the moment.

Thanks, Aaron. I am just curious because I can't imagine the gains being worth the trouble. But if they are, please let me know!

The more you are pushing the blower out of its factory limits, the more any of this work matters. It becomes thermally inefficient really fast. If you are trying to get a lot out of a gen 3, then the porting is very important. The gen 3 has some places it can use some help. IMO the biggest things are the outlet obstructions, especially the two bottom bolt receptacles that stick out into the outlet and the other thing would be enlarging the inlet neck to 75mm or whatever to match a bigger TB.

From what all I gather, the biggest thing holding the conventional roots supercharger back is it's ability to efficiently draw in it's air when it's really being pushed. It's moving the air out into the intake fine but if if it can't keep the inlet full of the air it needs fast enough, nothing works. There is a lot of vacuum on the inlet side during the moment when it's waiting for air to enter and to worsen this affect, you have a bunch of boost on the outlet side so there's a good 30psi difference between the two sides of the blower and all it wants to do is seep air backwards. You can see how it can become badly inefficient.

I think they're worth the trouble IF you have the right plan, and IF you have a 2nd blower/LIM to work on off the car. I couldn't justify having my car out of commission while I worked on a port//polish job. At this point I'm about to send mine up to Andrew (Karma) and letting him work on it, since he'd do a better job.

We can't really put an absolute HP number on P&P, because it all depends on what your engine makes right now. For a stock 240HP engine, you might gain 10-20 HP or more (ZZP claims 15% gain (36 HP). For a 300+ HP car, you might gain 25-30 (45 HP according to ZZP's claim). That's a substantial amount of power if they are right. I am skeptical, but it would seem to be definately worth doing if you have the time or money to spare. To put into perspective, that's more HP than a safe SC pulley swap will give you, and the pulley swap is definately noticeable.

Or you could just swap to Gen V and have a similar increase. Everything I've read seems to indicate a P&P Gen III = close to an unaltered Gen V.

What do you all think about P&Ping the body of the blower.. wouldnt that ruin the tight fit of the rotors and mess up the vacuum? even just 1mm would throw it off, i'd think.. But it looks like Codith did this to his genV and all is well? if you polish too much, the rotor pack would be like a hotdog in a hallway, ya know?

If you're talking about the inside of the housing, why would you want to do this?

AA wrote:

If you're talking about the inside of the housing, why would you want to do this?

I am. I wouldn't, I don't think. I don't know much about this, but isn't the inlet and outlet the only parts that should be P&Ped?


Like I said, I'm no pro, but I don't think there is anything to gain by polishing the inner housing of the rotor pack???

The way mine looks, the rotors were actually machined against the inner housing wall, so the gap is probably 1/1000" or 2/1000". That's pretty tight. If you change that, I'd think all boost would be lost. Maybe Karma can help here.

I didn't touch the rotor contact surfaces at all. All I did on the inside was smooth out all the factory cast surfaces on the inlet which is all in front or upstream of the rotor area. That first image there where you see the tape covering the needle bearings, it's that entire area that's rough cast leading to the throttle body. I'd be hard pressed to prove that helps much but it certainly can't hurt if you don't mind spending a ton of time/work on it.

Yup, you don't want to touch the rotor contact area.  If its sooty leave it that way.  Don't change it, hone it, or port it. If you do anything with it you will lose efficency of the blower.  It would be like taking the seals out of a pump.  One of the reasons that the Gen V is as good as it is is because of its rotor coating that is constantly wearing "into" the main bores, which keeps efficency up.  For the inlet you want to smooth out any casting flaws just up to that back wall you see the tape on in the above pictures.  Where the airstream hits the hump on its way to the ends of the rotors is a hot spot and smoothing it out makes a big difference.  You don't really want to open up this passage either since that will change the rotor inlet duration. 

Once upon a time people would do whats called "raising the roof", which is taking out some of the material at the top of the blower over the rotors. The ratonale was to give some more room for air to enter the rotors.  Do not do this.  Its been found to increase turbulance.  Flow is best when the air enters at the ends of the rotors only.  You can see this in eatons whole design trend from the M62 to the new TVS blowers. 

So, Charlie, inlet porting is porting anything along the inlet up to where it becomes the machined rotor bores. Normally its just smoothing out casting flaws, or somethimes its opening it up a bit to match a N* throttle body.

Hi guys, I just took my supercharger off and noticed the blades were really dirty and black, and they bay areas in the engine has black spots everywhere, what should I do to clean this? Or do I even need to clean it up?

There is no need to clean the rotors because anything that will clean grease and dirt could also potentially clean the teflon coating off the rotors. Also I'm pretty sure the coating is black so that could be what you think is "dirt". As far as everything else under the engine bay I like to use Simple Green because it is a very non-evasive cleaner yet very effective, Plus it smells good.

Nice! I will do that thanks!