I assume that you have an intercooler.

The intercooler creates a pressure drop, and at high RPM's the CFM's of air increases and so does the pressure drop. So if the MBC and wastegate maintain a constant pressure at the turbo, then the pressure at the manfold will be the boost set point, minus the pressure drops across the intercooler, pipes and throttle body etc. So as the RPM's increase the pressure will drop.

The full pressure turbos sense the pressure at the manifold and control the boost from there, so the pressure at the turbo in increasing at higher RPM's in an attempt to keep the pressure up at the manifold.

I suggest that you remove the hose from the compressor housing, at the MBC and block it off. Now find a way to run a 1/4 line from the manifold and use it instead. This will provide for more power at the higher RPM's. You will have to watch to see if the pressure wants to overshoot. If it does you will be reducing the adjustment. This will be a first, so you will have to report how the yin and yang balance out.

When you make the change, you will have to make a major change to the BMC as the pressure tap at the compressor housing is a bit wierd. It is not a good analog of the turbo pressure in the ducts.

If you can get a pressure tap above the throttle plate or just before the throttle body that would be better than the manifold itself. This will keep vacuum out of the line to the MBC, but if that is not convenient, go with manfold pressure. That might work out well. The advanced MBCs have a ball and spring arrangement that are an effective check valve. Vacuum should never be applied to the wasegate actuator.

So 1st and 2nd gears are a new experience?

posted by 208.24.17...

• Finally, Manual Boost Control valve installed in LPT engine..., Mariusz, Wed, 17 Oct 2001 04:53:46
  • Thanks!!, BillR, Thu, 18 Oct 2001 18:54:20
    • Re: Thanks!!, Mariusz, Fri, 19 Oct 2001 17:56:52
      • Re: Thanks!!, BillR, Fri, 19 Oct 2001 18:14:12
  • Brainstorming....Need Imput!!, patprice, Wed, 17 Oct 2001 10:19:56
  • Re: Finally, Manual Boost Control valve installed in LPT engine..., Dean, Wed, 17 Oct 2001 09:56:28 <-- Viewing This Message
    • Thanks Dean for your help - and here are some other questions..., Mariusz, Wed, 17 Oct 2001 11:14:21
      • Re: Thanks Dean for your help - and here are some other questions..., Dean, Wed, 17 Oct 2001 13:47:23
      • Manual boost valve, Mark, Wed, 17 Oct 2001 13:39:57

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