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Can someone explain how the above boost control setup would work. The valve on the left uses a vac source applied to the top of the diaphram which would effectively help hold the spring closed at high boost levels providing high boost than a single valve setup would. I assume this would be used to give a large boost control range (similar to a CO2 boost controller). Is this correct?

I'm not sure what the D port on the actuator does though, I assume that D and E are both connected and would both work against the spring opening it?

What control circuit would be required to drive the two valves. Would you need a split range controller with two different duty curves, or could you run them from a single controller with a single curve, eg run the two valves from a single PWM output?

  • 4
    I'm voting to close this question as off-topic because it is not about motor vehicle maintenance and repair.
    – Solar Mike
    Aug 16, 2019 at 4:06
  • This is a contril engineering question, probably bettet on another stack.
    – Solar Mike
    Aug 16, 2019 at 4:08
  • 1
    Cross posted here: engineering.stackexchange.com/q/29657/10902
    – Solar Mike
    Aug 16, 2019 at 4:09
  • Leave it open, there are smart mechanics, maybe someone can explain it. The photo is from a workshop manual for a 1.9L Skoda
    – rollsch
    Aug 16, 2019 at 5:23
  • Some of us are... but you would help your own question by putting info in the original question about make, model and problem you are trying to sort instead of making it “theoretical”...
    – Solar Mike
    Aug 16, 2019 at 5:28


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