CHRA/turbine bolts relaxing.
#205
Because Inconel has proven to solve this same problem (bolts stretching/relaxing due to high heat) at the manifold -> turbine housing joint
So we use inconel bolts because they do not "soften" or stretch the way stainless steel does (though we expect they expand and contract like any good bit of matter will under heat - they simply do so much more favorably than the SS or other metals do)
And we use safety wire to keep the good bolts from vibrating loose. Even though the inconel has a much more favorable heat propery, the heating/cooling of the turbine housing will occasionally cause the inconel bolts to become "free floating" in the housing (where once they were torqued, now they are not even "finger tight" simply because of the heat cycling/expansion between the bolt/housing) The safety wire simply keeps the bolts from loosening when this state is achieved.
SS bolts w/o safety wire --> bolts stretch and/or loosen
SS bolts w/safety wire --> bolts stretch
Inconel bolts w/o safety wire --> bolts loosen
Inconel bolts w/safety wire --> tight like a tiger
So we use inconel bolts because they do not "soften" or stretch the way stainless steel does (though we expect they expand and contract like any good bit of matter will under heat - they simply do so much more favorably than the SS or other metals do)
And we use safety wire to keep the good bolts from vibrating loose. Even though the inconel has a much more favorable heat propery, the heating/cooling of the turbine housing will occasionally cause the inconel bolts to become "free floating" in the housing (where once they were torqued, now they are not even "finger tight" simply because of the heat cycling/expansion between the bolt/housing) The safety wire simply keeps the bolts from loosening when this state is achieved.
SS bolts w/o safety wire --> bolts stretch and/or loosen
SS bolts w/safety wire --> bolts stretch
Inconel bolts w/o safety wire --> bolts loosen
Inconel bolts w/safety wire --> tight like a tiger
Last edited by fooger03; 02-24-2011 at 11:18 PM.
#206
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TiAL. They now come standard when you buy a turbo with their turbine housing too. They've made a few different styles the first of which did come predrilled for safety wire. I've taken a sample of each and ran 'em thru Jesel's SEM/EDS xray detector gizmo to get the alloy content, results posted in this thread. 30Rc.
With me spending so much time in the prototype dept
#208
My progression:
- standard bolt: failed, broken turbine
- Nimonic bolts: failed so bad they fell out in one session, almost damaged the turbine
- stardard bolt, SS wire: failed and stretched wire, almost damaged the turbine
- standard bolt, inconel wire: failed after 4-6 days, failed safe, drove the last session and 5-hours home without damage
- tial provides inconel bolt with no holes for wire: called TiAL, claimed they did't read my instruction and don't have equipment to drill inconel. I'm not pleased of the lack of support. If I could go back in time and buy Turbosmart parts with a 4-bolt flange and inconel bolts I would
Nimonic is a trade name registered by the same company that invented Inconel.
I think both are used for bolts inside jet engine turbines.
#210
Hey Hussie...here is some food for thought-
OK..big words, right? Well I remember the 'epic studs' thead and the discussion that on a lot of the manifolds (BEGI and FM) that the turbo-to-manifold studs were exposed to the raw exhaust gases causing the difference in material to prematurely get much hotter/expand at a different rate than the turbine housing whereas most others and OEM turbo cars do not have studs/bolts that are in contact with raw exhaust gases. Pretty sound theory if you ask me..though I am no M.E.
Anyway.
I just replaced my GT28 exhaust hausing and clearly remember that when I pulled the 8 housing bolts off, the tips were black with carbon. I just ran out into the garage and looked at the housing and the 8 bolt holes all go through to the inside where the bolts would be in direct contact with the superheated exhaust gases.
Soooooo.....maybe finding a way to shield the bolts from direct exposure? Yes? No?
Or you already knew this and it was mentioned somewhere between pages 5 and 9 that I didn't read carefully.
OK..big words, right? Well I remember the 'epic studs' thead and the discussion that on a lot of the manifolds (BEGI and FM) that the turbo-to-manifold studs were exposed to the raw exhaust gases causing the difference in material to prematurely get much hotter/expand at a different rate than the turbine housing whereas most others and OEM turbo cars do not have studs/bolts that are in contact with raw exhaust gases. Pretty sound theory if you ask me..though I am no M.E.
Anyway.
I just replaced my GT28 exhaust hausing and clearly remember that when I pulled the 8 housing bolts off, the tips were black with carbon. I just ran out into the garage and looked at the housing and the 8 bolt holes all go through to the inside where the bolts would be in direct contact with the superheated exhaust gases.
Soooooo.....maybe finding a way to shield the bolts from direct exposure? Yes? No?
Or you already knew this and it was mentioned somewhere between pages 5 and 9 that I didn't read carefully.
#211
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I just replaced my GT28 exhaust hausing and clearly remember that when I pulled the 8 housing bolts off, the tips were black with carbon. I just ran out into the garage and looked at the housing and the 8 bolt holes all go through to the inside where the bolts would be in direct contact with the superheated exhaust gases.
Hey hustler, try making a cool looking crane with heim joints to the turbine housing. That'd fix it. Full circle time again baby let's keep this thread rollin!
#212
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I'm still naming my first born Nimonic.
#216
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Damnit Jason you got me going now. http://en.wikipedia.org/wiki/Nimonic
I'm still naming my first born Nimonic.
I'm still naming my first born Nimonic.
I will.