Machined turbine wheels banned in x275

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allan5oh

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A little off the usual threads here, but in the gasoline world in x275 radial class (probably the most popular class by far) turbine wheels/hubs that have been machined are banned. Apparently this was a costly thing to do, but forced inductions was very good at it. Their turbos were winning and the class sponsor (precision) wasn't too happy.

Apparently if it was done right it frees up quite a bit of power, but if done wrong can reduce the reliability of the turbine. It's also slightly amusing that the majority of failures in this class are precision turbos that have NOT been modified, yet apparently this rule change is done for safeties sake.

I wish I had a pic of the machining process, but what it looks like is the thickness of the turbine shaft is cut down, it looks much narrower where you would normally put the socket on the end.
 
allan5oh said:
A little off the usual threads here, but in the gasoline world in x275 radial class (probably the most popular class by far) turbine wheels/hubs that have been machined are banned. Apparently this was a costly thing to do, but forced inductions was very good at it. Their turbos were winning and the class sponsor (precision) wasn't too happy.

Apparently if it was done right it frees up quite a bit of power, but if done wrong can reduce the reliability of the turbine. It's also slightly amusing that the majority of failures in this class are precision turbos that have NOT been modified, yet apparently this rule change is done for safeties sake.

I wish I had a pic of the machining process, but what it looks like is the thickness of the turbine shaft is cut down, it looks much narrower where you would normally put the socket on the end.
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You can order those straight from the manufacturer (in China).
 
Are they gt55's?

If so the market flooded with gt55's huh.
 
allan5oh said:
Apparently if it was done right it frees up quite a bit of power, but if done wrong can reduce the reliability of the turbine.
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I might have taken my stupid pills this morning, but walk me through how it makes more power.
 
WUnderwood said:
I might have taken my stupid pills this morning, but walk me through how it makes more power.
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Reducing the hub isn't what is increasing the power. Been done in Super Farm for a long time, it's obviously nothing remotely new.
 
From the pictures that were posted it does appear to be chinese turbines. The picture they posted showing what was banned on the account I looked at showed one of the chinese turbines casted with a very small hub.
 
Assuming this is what you all are referring too. Can definitely see the power increase potential but also the possibility for a increased failure point.
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Sent from my moto z3 using Tapatalk
 
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Yes that is the picture. A bit more information is needed. The class has three different compressor sizes at three different weight breaks: 80mm, 85mm, 88mm. Here's a direct link to the new rules as of Monday:

https://www.facebook.com/laura.sears.587/posts/10212888346397572

TURBOCHARGERS
Single turbocharger limited to 88mm maximum. *Garrett GTX GEN II/PTE XPR (using current X275 exhaust/turbine measurements) permitted with weight penalty. Turbocharger size will be verified by measuring the housing bore at the leading edge of the impeller wheel and must maintain the contour of the compressor housing. (Stepped compressor wheel prohibited) Inducer dimensions may not exceed 80.9/85.9mm/88.9mm and Exducer backing plate and blade tip to tip dimensions may not exceed 133mm on MID FRAME turbos except where noted. *The Garrett GTX GEN II/PTE XPR Inducer dimensions may not exceed 85.9mm/88.9mm, Exducer backing plate dimensions may not exceed 133mm. The Exducer tip to tip measurements may not exceed 142.5mm. On mid-frame turbo claiming 85.9/88.9 on tip to tip inducer measurements the inspection tool must capture .200 of the blade tip to be eligible for the latest deductions in weight. On LARGE FRAME turbos the inducer may not exceed 85.9/88.9mm and Exducer dimensions may not exceed 141.224mm. The maximum diameter of the housing bore at the leading edge of the wheel may not exceed 2 mm more than the maximum allowable turbocharger size permitted. Inserts or reducers to achieve inlet or outlet dimensions prohibited. Compressor map groove will not exceed .250 of an inch. Any turbocharger entry may be asked to remove the compressor cover and/or turbine housing for inspection. The turbine wheel may not exceed 113mm X 103mm on ANY turbocharger. Turbine wheels are only allowed to be constructed of Inconel material. Billet aluminum compressor wheel/impeller permitted. Any inconsistent modifications to compressor or turbine wheel, blades, hubs, cover, or housing, beyond accepted commercially available manufacturing process, is PROHIBITED.
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I am not sure how machining the turbine wheel adds power for a gasoline application, or if it does. That's why I brought this all up really. But here's what I do know:

Forced inductions switched to a 100mm turbine (probably Chinese) then a 102mm turbine (probably Chinese). The top guys in x275 and Ultra - probably the two most popular radial classes on the planet - both use FI turbos. Apparently the Ultra turbo is a "one off" that will never be made again.

Precision is a sponsor of the class and either a current or former precision employee has been "helping" with tech recently measuring stuff. Stinks to high heaven I know. The funny thing is Precision has or used to machine other manufacturers turbine wheels in the past. They also do NOT have a good reputation for reliability when pushed to the limit as I'm sure you guys know. So it seems rather odd that the class sponsor turbos are allowed even though they are not known to be reliable, and the "modified" turbos which are MORE reliable are banned all in the name of safety. Money talks.
 
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allan5oh said:
I am not sure how machining the turbine wheel adds power for a gasoline application, or if it does. That's why I brought this all up really.
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That's why you brought this up? Sounds like you are pushing a different narrative with your comments. You honestly believe a company as large as Wabtech the parent company of Precision Turbo needs to play those games?
 
Smokem said:
That's why you brought this up? Sounds like you are pushing a different narrative with your comments. You honestly believe a company as large as Wabtech the parent company of Precision Turbo needs to play those games?
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I guess I am. Just thought the whole thing played out a bit funny. But I am genuinely curious what modifications these banned turbos have and how much they help.

To be clear, X275 doesn't allow stepped compressor wheels and they're likely running a PR around 3.5-4.
 
smaller hub means more area the air can flow, reduced driver pressures and increase leverage on the hub by increase blade surface without increase turbine diameter..
according to the pictures posted... the small hub turbine appears to have substantially thicker blades vs the thick hub turbine
 
Smokem said:
That's why you brought this up? Sounds like you are pushing a different narrative with your comments. You honestly believe a company as large as Wabtech the parent company of Precision Turbo needs to play those games?
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Dis.




I don't think people grasp how large Wabtech is. They paid cash for Precision and a couple other companies in the same year if that tells people anything.
 
So because a parent company is large, this company would never do something like this?

I'm not sure what you guys are getting at.
 
zfaylor said:
From the pictures that were posted it does appear to be chinese turbines. The picture they posted showing what was banned on the account I looked at showed one of the chinese turbines casted with a very small hub.
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Or maybe NR turbines ?
 
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