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Breaking on boost!!! issue

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  • Breaking on boost!!! issue

    Dear,
    when you brake on boost ( I mean when the turbo is charging pressure) the brake pedal changes it's sensitivity, it gets harder and delivers the feeling that the brakes lose effectiveness.

    Check this situation:
    1) accelerate
    2) turbo starts boosting
    3) try brake

    You will see that the pedal gets harder and you have to push harder the pedal.

    Have you experienced this?

    Is there a way to improve this situation?

    I've changed the brake fluid three times even more I put braided lines and brembo brake pads but the sensation is the same. It's appear is a defect in the design? or it is a trouble in my brakes?

    Your help is appreciated.

    PD: some friends of mine experiment the same.

  • #2
    In other words, when you brake in boost, the pedals feels a lag reaction.

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    • #3
      Sounds like your not getting enough servo assist? Has the vacuum pipe come off or chaffed through to the servo?

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      • #4
        Originally posted by caino6 View Post
        Sounds like your not getting enough servo assist? Has the vacuum pipe come off or chaffed through to the servo?
        How can I check this?

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        • #5
          Put your foot on the brake, then start the car up, if pedal sinks slightly to the floor then the servo is working, if it remains hard then the servo is not working.

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          • #6
            ok I'm going to check to confirm this.

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            • #7
              You shoulnd't be able to brake and boost at the same time? If I try this, my car opens the recirc valve to kill the boost pressure. I guess this is a fail safe to prevent engine damage.

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              • #8
                Originally posted by Jonnie_VXR View Post
                You shoulnd't be able to brake and boost at the same time? If I try this, my car opens the recirc valve to kill the boost pressure. I guess this is a fail safe to prevent engine damage.
                Certainly you're right , but what I mean is: accelerate (increasing boost), then release accelerator then brake. Maybe you can feel that brake pedal gets harder.

                The situation described above maybe exemplified when you're chasing other car, you accelerate and suddenly it brakes hard forcing you to brake hard. In this situation maybe you experiment what I described. If you can, try this in a open a clear road:

                Accelerate (increasing boost) then brake and feel the pedal feedback.


                Compare the pedal feedback with the situation when you just brake when your boost is 0 or you are in vacuum (-19psi).

                When I say feedbak=assistance, hardness, effort that takes to brake effectivily.

                Try and tell me please, what do you experiment.

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                • #9
                  Originally posted by caino6 View Post
                  Put your foot on the brake, then start the car up, if pedal sinks slightly to the floor then the servo is working, if it remains hard then the servo is not working.
                  I checked, and the servo is working.
                  But, when you brake on boost, the pedal gets harder.

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                  • #10
                    Check the one way valve in the hose to the servo.

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                    • #11
                      Originally posted by andrewt1971 View Post
                      Check the one way valve in the hose to the servo.
                      what I must expect?
                      How can I check if it's working?
                      where is it?

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                      • #12
                        Is this the valve?
                        Last edited by Rreivid; 7 September 2017, 05:58 PM.

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