Smoothing out inside of evo3 16g cover?

[frankenstein406]

I'm rebuilding my evo3 16g and the compressor cover seems to have a lot of rough spots from the casting. If i smooth them out will i see any noticeable flow increase to justify doing this? Guessing this will make it more efficient? What grit sould i start with 50 100 or dremel?

 

[romeen]

IMO, since you have it apart I would do it. I did it to mine and it definitely seems like the turbo is more eager to spool and pulls a bit harder in the upper rpm's. But I don't have any objective data to back this up so take if for what it's worth.

Mike at RRE actually convinced me to do it. The way he worded it was that if someone were to do this to your turbo while you slept but didn't tell you, you would notice that the car was performing better the next time you drove it. Again, take it FWIW.

I used the small sanding drums/rolls (used in head porting/polishing) with an air die grinder. But since the aluminum is so soft a Dremel should work fine. I don't recall which grits I used but the aluminum is easy to work with.

Don't get carried away and don't remove material from the area around the compressor blades. I just opened the diameter of the outlet and extended that down into the neck of the compressor outlet a couple of inches. Don't go too big on the outlet. Leave enough material to allow a good seal with the j-pipe. You may have to use RTV silicone to seal it since the opening of the factory style gasket will be too small.

 

[DSMunknown]

People should be using RTV anyways. One less worry for leakage.

 

[JusMX141]

People should be using RTV anyways. One less worry for leakage.

...until you send your turbo in to be rebuilt and it takes the rebuilder 20-30 minutes to remove the compressor cover that you glued on with RTV. That tends to make the rebuilder an angry person.

 

[romeen]

I'm pretty sure Anthony is talking about using RTV between the compressor outlet and j-pipe flange.

 

[frankenstein406]

I cut my own gaskets instead of using rtv.