I've just been told this is not a clipped turbine wheel

bradsm87

Corporal
Dec 15, 2016
162
53
0
I've just been told this is not a clipped turbine wheel.

It looks clearly clipped due to not only the machining but also the blades ending before they get much curvature on them. I'm very open to be proven wrong.

Is there any way that this turbine can be called "not clipped"?

Turbine.png
 

Bmwfixerguy1

Lieutenant
Jun 5, 2017
873
288
0
Ride
07 335i MT
Looks pretty clipped to me as well. I could be wrong but visually that's what clipped always looked like.
 
Feb 8, 2018
23
14
0
Ride
Focus RS, Impreza RSti
I am not trying to be disagreeable with whoever told you that, but it certainly looks like the top of the blades were ground down or clipped. Here is a picture of a similar 9-blade TD06H turbine wheel of a similar design puled out of a failed turbo a customer sent in. The top of the blades are not clipped. The difference should look obvious.

Clipping is an old-school hack. It can increase the turbine section flow, but kind of wrecks the areo of the turbine wheel. It basically make it much less efficient. Normally improved flow does not offset the drop in efficiency performance wise. The trick can workout sometimes if you are stuck with say the OEM turbine wheel and housing, and are adding a high flow comp wheel. Anyway, if you are making a new turbine wheel anyway, you can just size it correctly such that it flow well enough without clipping. You get the flow you need, and keep the wheels efficiency.

IMG_20180409_230133.jpg


As a side note, we also use similar 9-blade turbines in our STI turbos. We have also gas bench tested them and have compressor and turbine maps for them which we posted below.

Pros for the 9-blade turbine wheel like this:
- low mass = low moment of inertia = faster response
- tiny hubs = low mass & more blade area
- flow great for size

Cons:
- poor efficiency (52% vs Garrett's 72%)
- low harmonic frequency = potentially lower RPM potential and durablity
- tiny hub = high blade failure risk due to stress at the junction of the blade to the hub

With all of that said, they worked well for our JB STI turbos, so we continue to use them.

-Sam

https://blog.steamspeed.com/2015/03/12/steam-stx-71-flow-testing-part-2-stx-71-vs-gtx3071r/

Here is our published map:
STX-71-turbine-map-768x569[1].png

Our TD06SL2 vs a Garrett GTX30 turbine:
STX-71-vs-GTX30-turbine-map[1].png
 

bradsm87

Corporal
Dec 15, 2016
162
53
0
I am not trying to be disagreeable with whoever told you that, but it certainly looks like the top of the blades were ground down or clipped. Here is a picture of a similar 9-blade TD06H turbine wheel of a similar design puled out of a failed turbo a customer sent in. The top of the blades are not clipped. The difference should look obvious.

Clipping is an old-school hack. It can increase the turbine section flow, but kind of wrecks the areo of the turbine wheel. It basically make it much less efficient. Normally improved flow does not offset the drop in efficiency performance wise. The trick can workout sometimes if you are stuck with say the OEM turbine wheel and housing, and are adding a high flow comp wheel. Anyway, if you are making a new turbine wheel anyway, you can just size it correctly such that it flow well enough without clipping. You get the flow you need, and keep the wheels efficiency.

As a side note, we also use similar 9-blade turbines in our STI turbos. We have also gas bench tested them and have compressor and turbine maps for them which we posted below.

Pros for the 9-blade turbine wheel like this:
- low mass = low moment of inertia = faster response
- tiny hubs = low mass & more blade area
- flow great for size

Cons:
- poor efficiency (52% vs Garrett's 72%)
- low harmonic frequency = potentially lower RPM potential and durablity
- tiny hub = high blade failure risk due to stress at the junction of the blade to the hub

With all of that said, they worked well for our JB STI turbos, so we continue to use them.

-Sam

https://blog.steamspeed.com/2015/03/12/steam-stx-71-flow-testing-part-2-stx-71-vs-gtx3071r/

Thanks heaps for the informative response and honesty regarding both pros and cons of the 9-blade small hub turbine.

Would you be interesting in producing a "Stage 1.5" turbo for N55 for those that want more than just a compressor upgrade but do not need all the capability of a Stage 2 turbo? Eg. "STX 71R"?
 
Feb 8, 2018
23
14
0
Ride
Focus RS, Impreza RSti
Thanks heaps for the informative response and honesty regarding both pros and cons of the 9-blade small hub turbine.

Would you be interesting in producing a "Stage 1.5" turbo for N55 for those that want more than just a compressor upgrade but do not need all the capability of a Stage 2 turbo? Eg. "STX 71R"?

Yes, I think that would actually be a great idea. Vincent is currently just on the 3rd revision with 16 psi of our STX 78R, an it is already making over 500 ft*lbs at 4700 RPM. I sure it will be even more bonkers once he hits 25 psi or more. Vincent says the 78R is already a lot to handle even at 16 psi, stage 1 at maxed out at 400 whp felt a lot more balanced to him.

A 71R would probably get you to the 450-500 whp range which I think would feel great. We could make it a little bigger than 71mm, if you want to be sure to have at least a 500 whp capable comp wheel. I think I would personally go that route. For my Focus RS, we made 76Rs that make over 500 whp, and 71R. I will be driving the 71R.

Anyway, PM if you are interested in trying out a 71R BB N55 turbo, or maybe a 73R if you want it a little bigger.

-Sam
 

terryd5150

Specialist
Mar 4, 2017
87
26
0
Ride
2008 E92 335i 2009 E90 335i
Yes, I think that would actually be a great idea. Vincent is currently just on the 3rd revision with 16 psi of our STX 78R, an it is already making over 500 ft*lbs at 4700 RPM. I sure it will be even more bonkers once he hits 25 psi or more. Vincent says the 78R is already a lot to handle even at 16 psi, stage 1 at maxed out at 400 whp felt a lot more balanced to him.

A 71R would probably get you to the 450-500 whp range which I think would feel great. We could make it a little bigger than 71mm, if you want to be sure to have at least a 500 whp capable comp wheel. I think I would personally go that route. For my Focus RS, we made 76Rs that make over 500 whp, and 71R. I will be driving the 71R.

Anyway, PM if you are interested in trying out a 71R BB N55 turbo, or maybe a 73R if you want it a little bigger.

-Sam

PM