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Diaphragm intallation into wastegate problem

Dear all,
I replaced a torn diaphragm on a 1977 Turbo recently.

Unfortunately I have problems getting the diaphragm sealing off properly. When testing the unit with air pressure of about 1 bar I can hera and feel that some air bypasses the diaphragm. The diaphragm ist fine, but it is not sealing properly with the body of the wastegate.
Is there any trick or method to improve this?

Thank you for any tips on this.

Kind regards,

cal
Old 06-09-2010, 11:18 PM
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It could be air going by the valve stem. If the wastegate opens at the correct pressure that small amount of air leakage is fine.
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Dean
911 SC turbo, 3.0L 930 motor, G50, 930 brakes, DTA EFI, 352 RWHP DynoDynamic dyno,
Old 06-10-2010, 03:21 AM
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Quote:
Originally Posted by dean View Post
It could be air going by the valve stem. If the wastegate opens at the correct pressure that small amount of air leakage is fine.
^^^ +1. Run the car, it will probably be fine. Valve guides and/or seats age and can pass a small amount of air.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 06-10-2010, 04:44 AM
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+1 to what Dean and Mark stated but you also need to make sure the edge of the diaphragm is contacting the aluminum base where the wastegate bell attaches. If the diaphragm is too high, the bell will not seal the diaphragm properly and air will escape from area where the bell bolts to the base.
Old 06-10-2010, 05:25 AM
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The 930 wastegate is not a precision instrument it's a simplified pressure actuated relief valve. Functionally it works quite well under extreme conditions but
practically it is a step or two above the flush valve in your toilet. In most cases it will keep the heads from blowing off you engine but, if it were perfect, you wouldn't have an overboost switch.

You can spend $400-$600 and buy a polished, pretty, painted one that does exactly the same thing in exactly the same way but it looks much better doing it.
If it's a real concern to you, your best bet is probably an electronic boost controller that uses a solenoid valve that keeps boost pressure from reaching the wastegate until a preset is reached and then blows the wastegate open almost instantly.

Now, this runs us all the way around the barn and back to the door. There is probably a perfect solution that totally escapes me but in the words of my wise Grandfather "with perseverance and a little sweet oil you could f--- a cat" But in the interim make sure your overboost switch works.

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.

Last edited by cole930; 06-10-2010 at 12:22 PM..
Old 06-10-2010, 06:41 AM
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...a step or two above the flush valve in your toilet.
...."with perseverance and a little sweet oil you could f--- a cat"
Cole
Cole, thanks for the laugh this morning! Desperatelly needed.
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Old 06-10-2010, 07:44 AM
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Anything to help ........ When times are bad and the s--- is coming down hard you have 2 choices, you can get a bigger hat or ya can hold your breath and go deep because s--- floats.

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 06-10-2010, 12:14 PM
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Dear all,

thanks for your answers. I will try tomorrow how it works under driving conditions.... before once again checking if the diaphragm sits properly in the housing :-)

Cheers, cal
Old 06-10-2010, 01:14 PM
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