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Old 11-28-2012, 11:18 AM   #657
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Originally Posted by yamahaSHO View Post
If you lower the WGDC, it will open the port more directly to the WG diaphragm via the EBCS. 100% WGDC should put the MBC solely in the loop for boost control.


0% = Spring pressure
100% = MBC
1-99% = Boost control anywhere between spring pressure and MBC.

It works.
ORLY? Thanks for explaining something I've known and used for the past 5 years. J/K, this thread is pretty long so I don't expect you to read that far back.

Originally Posted by yamahaSHO View Post
The only optimal way I've found after countless cars is the way Grimmspeed recommends. Using the inlet caused overboosting as I was essentially using the inlet vacuum to lower the pressure on the line needed for opening the WG.
I did not experience any overboosting. Just rock solid boost control at any throttle position, gear, RPM, etc. The phenomenon you described would result in the need for less WGDC for the same boost pressure. That's not a good or bad thing, just different. Are you sure you're tuning it correctly? Then again, I did run a lot of boost, and 'overboosting' isnt much of a concern when you're at the outer limits of available boost pressure.

But what you say is plausible. The vacuum in the inlet reduces the pressure on one side of the MBC so it 'sees' less of a pressure differential and opens the wastegate less which is basically equivalent to setting the MBC a little higher. But then can't you just loosen up the MBC a bit to compensate?
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Last edited by MRF582; 11-28-2012 at 11:35 AM.
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