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Loose CHRA, but bolts tight? Wha?

Old 09-17-2014, 03:40 PM
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Default Loose CHRA, but bolts tight? Wha?

Was checking water hoses to make sure the rubber wasn't hardening/cracking yet, grabbed one of the hoses and wiggled it - lo and behold, the entire CHRA wiggles with it... (turbo was hot at the time, since cooling down the movement is much more minimal, barely a tiny wiggle, maybe 1/32")

Checked bolts holding CHRA to turbine housing, they are still tight.

Am I missing something obvious? Is this normal? This is an IHI RHB5 turbo from a Cartech/early BEGI kit, as far as I'm aware the turbo is assembled correctly. Bolt + hold down tab threaded thru the CHRA flange into the turbine housing, and again, they're tight!

It looks like the tabs aren't actually pressing against the CHRA flange, like there is a slight gap. Not sure how this could be, like there needs to be a shim of some sort under the tabs... Any thoughts? Thanks

Pic:
Attached Thumbnails Loose CHRA, but bolts tight?  Wha?-imag0517_zps0bca602b.jpg  

Last edited by sbcrx007; 09-17-2014 at 07:22 PM.
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Old 09-17-2014, 09:59 PM
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I would imagine your bolts are just a 1mm or so slightly too long and the bolts are bottoming out in the housing before the shims can be properly tensioned. You could try removing a little bit of the bolts or add a washer to it.
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Old 09-17-2014, 10:21 PM
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I'll double check, but I'm pretty certain the bolt is bottomed on the tab/housing. You can actually sort of see the gap in the picture, its between the tab and the CHRA flange; adding a washer anywhere won't help.

Moreover, this piece is circa 1990 or so and has presumeably running fine all this time, until falling into my hands... Why is it loose now?

My concern is the turbine wheel blades hitting the turbine housing, as evidenced by other folks here when their CHRA bolts broke/stretched/fell out. My bolts are still tight, so this seems to be a slightly different case..
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Old 09-17-2014, 10:23 PM
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warped maybe?
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Old 09-17-2014, 11:43 PM
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Or cut the edge off a washer and put it between the shim and the CHRA to help the play. Since the turbo has had a long life maybe the shims have been compressed a little.
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Old 09-18-2014, 08:30 AM
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Originally Posted by 18psi View Post
warped maybe?
The turbine housing, or the bolts? Don't think so either way...

Or cut the edge off a washer and put it between the shim and the CHRA to help the play
That's more or less what I was thinking, but the hold down tabs don't seem to be bent/warped/worn in/etc.. they look fine. Just somehow the CHRA seats too deep into the turbine housing, or something.

I've got 1 or 2 trackdays left this year to run, think its safe to leave it alone and run it, or add shims and run it?
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Old 09-18-2014, 06:30 PM
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I'd rather get a little peace of mind and shim it. Then after the season address the root of the issue by pulling the turbo and see what black magic voodoo **** is going on.
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Old 09-19-2014, 11:15 AM
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That's pretty much my thought as well... Doesn't seem to be any play between the cold side and hot side, other than being able to rotate it slightly. I guess it's possible that the looseness is designed in to compensate for expansion at full temp or something similar.
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