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

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.

+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.

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

Cole, thanks for the laugh this morning! Desperatelly needed.

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

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