Should be ported already by Corky when I pick it up

 

OK I picked up the kit on Friday and it was indeed ported. Corky showed me where the modifications were done. Most of the material was removed (ported) in the area between the exhaust manifold flange and the wastegate area. The wastegate hole was opened up a bit as well.

Yes I know... TTIUWP... pictures coming soon...

 

yep

 

I was unable to photograph some of the mods. But here is one. I would not recommend that you do this at home though.
Stephanie

 

My turbine housing looks EXACTLY like that one... because it is that one
Some more pictures. I processed these so the sharpness is much higher to exaggerate the details. The flange surface for example is smoother than how it looks here.

 

So thats whats meant by porting the wastegate. I thought it was opening the hole more.

 

This image was taken looking through the exit side of the wastegate, back towards the exhaust flange (looking upstream). The arrow points at the area where the material was removed. You can see the resulting arc shape in the casting.

 

The idea as explained to me by Corky is that the gases have a more direct path to the waste gate area. Loosely speaking, they do not have to change direction as quickly. The porting makes the change in direction of flow more gradual, thus resulting in better flow into the wastegate pocket.

 

^ Very interesting. I wouldnt have thought that would ever make a difference. I was constantly under the impression it was making the wastegate opening bigger. Seems to me there is some room to gain, how come they arent opened more?

 

Well I am guessing here, but based on the general understanding I have of flow (I am a Mech Engineer) as far as waste gate size goes
- There needs to be a certain amount of overlap between the waste gate valve face and the waste gate opening in order for it to seal properly. Leakage at low boost levels would mean slower spool times. The valve can only be so big in the housing due to space limitations, thus indirectly limiting the size of the port.
- If the opening is a lot larger, then the flow transition as the wastegate valve opens would be much more abrupt, possibly leading to instability in boost control. That is a guess though.

 

I'd be willing to say it is because there is more cost to do the extra work by the people making the cast pieces.

We manufacture cast products for our equipment and the more finishing that is done to the device at the end all costs us more $$$ overall. So there is a fine line between functional and works as specified vs. optimal and high performance.

Cheers,
Prospero

 

Yes, that too, good point. I did a little casting design work in my earlier days so I know enough to be dangerous. If you look at it, it would be hard to pull the core out of the casting with it tapered the way it is in the modified version, assuming it was sand cast, which it probably was. Of course there is always investment casting, which allows for flexibility in design, but that is more expensive for production pieces.

 

No doubt that it's a sand cast piece... and you're right about investment casting being the way to fly; just getting my engineers to keep from designing outside of what we built into the cast is the hard part. We cast a square today and they'll make an oval tomorrow.

Cheers,
Prospero

 

Here is a good article on high-end, racing application turbos compared to production turbos. There is some discussion in there on turbine housing design.
http://www.mazdausa.com/MusaWeb/disp...ession4&bhcp=1

5-axis CNC machined compressor wheels... CHA-CHIIING!

 

When going through my recent manufacturing magazine from SME I was suprised to see between 7 and 10 ads showing some kind of turbine/compressor wheel being machined by 5 axis mills. Very impressive to see the kind of work they can do. Thats also when you get into the realm of composite turbine housings and titanium internals.

Edit: That's funny, seen that article before, hadn't looked at it until after i typed this. I got to see one of those "elite" turbos, they were using it on a particular MSMS car at the time.

 

Yeah that makes a good ad for a mil considering that is a pretty complex profile to machine!

 

damn now I need to find some time to pull my turbo and send the exhaust housing back to bell

 

The porting shown in post #28 above is IDENTICAL to the porting recommended (required?) when installing catless downpipes/free flow exhausts on VF39-equipped Subaru's. The reason? To avoid/cure boost creep. Many have opened up the diameter of the port excessively with disastrous results. The technique shown and described above is how it should be done.

Scott

 

when Tim did mine he did both the path to the wastegate and the opening itself. i have no boost leak issues.

 

That does not make sense at all. A free flowing exhaust system should let the exhaust gases exit more quickly = less boost creep.
I had the same problem with the Begi S. Corky tried to help me and said that he would check one of his own gt2554 and call me back. He never did, I ended up porting the turbo myself as I cant afford to not having a running car for a month waiting for them to port it.
Now that it's ported it wont boost creep as much, only when it's cold weather