Wtf Has Been Done To My Turbine Wheel (Weird Blades Cut)

[jibe]

I have a IHI RHC7 turbo on my RB26.
I removed it last week because I need to fit a bigger turbine housing. The one that was bolted was really tiny.
So I removed the old turbine housing and discovered that my turbine has a weird blades cut. It's not a cut back or clipping. The cut is done at a different place.
A portion of the "major diameter" area working at the inlet side has been cut to be now the same diameter as the "minor area working at the exhaust side.
So we can conclude that there is an area where the blades of the turbine are now NOT tangent with the turbine housing, where the diameter is progressively reduced.
WTF is it intented for?
What effect does it have on spool up and top end?
Here are pics of my wheel and pics of a stock wheel.

Please, Turbo gurus, help needed!

[ZRBE]

I have no knowledge on this but did read a performance imports magazine that was talking about different style (cut) blades you can get for different results.

[jibe]

And does one of these cut styles match with mine?

[GTScotT]

Can you please point out where you think its been cut? I don't think anything has been cut from that photo.

[SargeRX8]

I don't think its cut, I think the design of the wheel is just different to what you were expecting.

My wheel looks like a pyramid shape. Its got some tiny dents on the fins from no idea what went into it. I was going to send it back to Tao to get it fixed and he said he would shave about a mm or what necessary to remove the imperfections. When asked what this would do to performance, he said there might be tiny gains up top.

Edited June 27, 2013 by SargeRX8

[jibe]

Here is an explanation pic, I hope it helps and hope it's more clear.

[luke gtr]

if it worked before, I wouldnt worry about it too much.

or, good excuse to buy new turbo?

[RobertPaulson]

Check the depth of the housing to the old blades and see how far off they were.

By cutting it back where you are saying they have, I think, would reduce exhaust temps by passing gasses onto the exducer much faster. If it has been cut there and you are sure of it, it's possibly to do with the small housing it has

[GTScotT]

Maybe ask Hypergear what he thinks, and how much he would charge to make the right housing for it?

[jibe]

I do confirm there is space between housing and blades at the place where it should be tangent.

I came at the same conclusion that it's made tu reduce backpressure, but now that I'm going to fit a bigger housing, I would like to ensure I will not loose too much energy to reach my power needs.

In fact, this wheel is now half way between Ptrim and GT35R wheel, so, knowing that I'm looking for 600bhp, it should do the job, but I wanted to share with better knowledged guys.

[hypergear]

By trimming down the inducer height can result in increasing of response as gas velocity is higher when they squeezing though smaller gap. Been used on a smaller engine previous perhaps assume it had the right turbine housing, or it might be be people experiencing concepts.

To make this work the turbine housing needs to be sleeved up to the height of the wheel tip then machined to suit the wheel profile. Can be done.

[jibe]

THanks,

The housing profile does what is drawed in green on the pic => so one half of the gases section hits the big diameter of the blades and one other half hits the small (and final) diameter of the blades.

I actually get 1.2bar boost peak at 3700RPM with the tiny housing (I measured the A/R and it's .40 A/R !!!!!), but the engine then chokes at 300whp.

Is it worth putting a bigger housing and keeping this wheel?

[hypergear]

Well, with the current turbine housing on it won't make any differences compare to before the turbine wheel was grinded.

We can supply a .63 or .82 turbine housing that is machined to suit your wheel. With a customized wheel it is hard to approximate the output.

[jibe]

Thanks, but I don't think it's Worth sending the turbo to you and them sending it back to me thought I live in west europe.

[GTScotT]

LOL OH, had no idea you were in Europe.

Even though it comes on very early at present I am not sure that will be the case with the new housing... But a reasonable turbo outfit in your area should be able to machine a sleeve as noted by Stao. I would definitely look at doing that, rather than running it as is.