wastegate open. The only way to open the wastegate is supply the wastegate
actuator with a control signal. This only works if the wastegate actuator
is functioning correctly. If your overboost problem is associated with
the actuator, using a MBC will not work.

A properly functioning wastegate actuator works like this.
It has a mechanical spring on one side of a diaphram.
This spring wants to keep the wastegate shut. The other
side of the diaphram is connected to a pressure line. When the pressure in
the line is sufficient to overcome the the spring pressure, the wastegate will open. If you hooked the high pressure side of the turbo directly to
the wastegate actuator, the wastegate would open at 6 to 7 PSI of boost or
at the base boost value.

The reason you can get more than base boost is that the BPC valve reduces the pressure in the control line by opening and closing the valve as commanded
by the ECU.

The valve has 3 lines and an electrical connector. The electrical
connector supplies signals from the ECU. 1 of the lines on the valve is connected to the high-pressure side of the turbo. The 2nd line is connected
to the low-pressure side of the turbo (essentially ambient pressure), and
the 3rd line goes to the wastegate actuator.

With a little bit of poetic licence, the valve supplies the high-pressure
signal from the turbo to the actuator at low boost pressure, up to base boost.
When the ECU decides more boost is needed it causes the BPC to switch to the low-pressure side of the turbo. The actual pressure at the actuator is the
average value between the low pressure side and high. The average changes
by the duration the BPC is porting low pressure v.s. high pressure.
In reality, the BPC valve is being switched back and forth many times a
second.

A manual boost controller replaces the function of the BPC valve. So it essentially
disables the ECUs ability to control boost.

Hope I have made this somewhat clear.

jj

• Aero B-b-b-boost Question! Please Help!, Brian, Fri, 20 Jul 2001 11:20:39
  • A bit of a shot in the dark..., BillJ, Fri, 20 Jul 2001 18:37:04
  • Re: Brian, the problem you are describing is fuel interruption, aero guy, Fri, 20 Jul 2001 14:51:58
    • AG, can you elaborate on how one would do the tests you..., Bill Cannastra, Fri, 20 Jul 2001 15:22:50
      • Re: Bill, I am a little confused are you Bill J in London or ano, aero guy, Fri, 20 Jul 2001 16:42:44
        • Thanks, AG. Is it possible for a novice to measure base..., Bill Cannastra, Sat, 21 Jul 2001 14:13:45
          • Bill- it could be a bad bpc valve, James, Sun, 22 Jul 2001 09:48:55
      • Re: Bill, I am a little confused are you Bill J in London or ano, aero guy, Fri, 20 Jul 2001 16:06:14
        • Bill Cannastra: London, Ontario, Canada ; not Bill J..., Bill Cannastra, Fri, 20 Jul 2001 16:39:08
          • Re: Sorry I just got confused working three places same problem, aero guy, Fri, 20 Jul 2001 20:20:04
  • Re: Aero B-b-b-boost Question! Please Help!, Jim in VA, Fri, 20 Jul 2001 12:08:41
    • I am in this boat as well, and it is taking on water!, chudzik, Fri, 20 Jul 2001 13:42:04
      • Are you hitting the boost cut-off? That's a really, jj, Fri, 20 Jul 2001 14:09:01
        • Re: Are you hitting the boost cut-off? That's a really, Brian, Fri, 20 Jul 2001 14:18:54
  • It could be ignition, try a new set of correctly, jj, Fri, 20 Jul 2001 12:04:45
  • Re: Aero B-b-b-boost Question! Please Help!, sully, Fri, 20 Jul 2001 11:28:46
    • I thought I was the only one..., Bill Cannastra, Fri, 20 Jul 2001 11:57:32
      • Bill, you really don't want to experiment with, jj, Fri, 20 Jul 2001 12:13:47
        • I'll be carefull, JJ., Bill Cannastra, Fri, 20 Jul 2001 14:19:46
          • I'm not sure I follow your logic on using a MBC to, jj, Fri, 20 Jul 2001 14:56:32
            • JJ, perhaps I'm off base, but my understanding of the MBC..., Bill, Fri, 20 Jul 2001 15:10:18
              • The only way to bleed off boost is to make the, jj, Fri, 20 Jul 2001 16:38:37 <-- Viewing This Message
    • Sully..., Brian, Fri, 20 Jul 2001 11:52:29
      • Re: Sully..., sully, Fri, 20 Jul 2001 16:22:41

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