Putting together a hybrid turbo this off season and have a question to those who have had the stock turbine housing machined to fit a P-trim turbine.

Did you have to change the contour/profile on the inner side of the housing?
OR
Did you just enlarge the major/minor and didn't mess with the contour/profile?

Thanks!

 

I didn't do the work myself, but I had my BNR Stage 4 apart many times and even got right in the exhaust wheel area of the exhaust housing to port the scroll slots wider.

On my BNR it appeared the exhaust housing was machined to accept the center housing as well as machined to match the diameters and contours of the "P" trim wheel.

I can tell you from experience on the rotary the exhaust wheel to exhaust housing interface does not have to be a perfect fit.
At one point when my BNR was being rebuilt I ran my stock turbo in the BNR exhaust housing bored out for the "P" trim wheel and it actually spooled fine with that huge gap around the exhaust wheel.

I shared this info with another member and they also set up a turbo with a bigger exhaust wheel sized exhaust housing to actual exhaust wheel set-up and they reported it also spooled fine.

So, you have lots of leeway in your machining.

 

Perfect! That's exactly the information I was looking for.

I'm going to machine the major/minor to have a 0.020" clearance and only touch the contour should I even need to.