Should a Boost Gauge show Vacuum?

Discussion in 'General Technical Questions and Answers' started by Kellen@Craven, May 20, 2013.

  1. Kellen@Craven

    Kellen@Craven New Member
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    Let's say you were designing your own boost gauge, would it be just a boost gauge or would you want to see it display vacuum as well? I would like to hear your thoughts and have a conversation about it...
     
  2. Mr. Jim

    Mr. Jim Mudshark
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    Should display both as the gauge will see both conditions. Vacuum lets you know how your engine is running also. My 2 cents.
     
  3. Kellen@Craven

    Kellen@Craven New Member
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    Thanks for starting Mr. Jim. If the gauge shows vac, should it be on the same scale, or do you just want to know that there is vacuum at all?

    The trade-off would be the amount of sweep available for boost readings. If half of the gauge is the vacuum side of things, then it becomes tougher to distinguish between 12 and 13 psi, right?
     
  4. DneprDave

    DneprDave Well-Known Member
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    In the USA, the vacuum should be in inches of mercury and the pressure should read in pounds per square inch.

    Or in Europe, vacuum in millibars and pressure in bars.

    Dave
     
  5. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    This is a valid question.... Just because the gauge will "see" vacuum doesn't necessarily mean you have to display that. I get where you're coming from, Kellen.

    Lots of folks have no real idea what the vacuum numbers mean... Nor interest in them. But have lots of interest in accurate boost....
     
  6. BThayer23

    BThayer23 Well-Known Member

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    Vacuum shows you when the bypass valve opens. Otherwise, not as useful as boost.

    I limped my car home from the track one time with a busted crank pulley - kept the car in vacuum around 45mph and it didn't throw codes or go into limp mode. But that was not a typical situation.
     
  7. Dave.0

    Dave.0 Helix & RMW Powered
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    The one I have shows vac and boost. I like it to show both.

    Here is the one I have:
     

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  8. SacredDisorder

    SacredDisorder Because Race Car?
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    I think Vacuum is a useful thing to show on the guage. Seeing how much vacuum your car pulls on a day to day basis can help to diagnose problems later down the line. Most electronic monitoring devices don't record the full readings of vacuum like a guage does either. My access port and REV for iPhone both show a max of 10-12 inches of mercury but my pro sport boost guage reads 23 inches while off the throttle coasting and 20-22 inches while at idle. Personally this is information I like to have.
     
  9. CarlB

    CarlB Active Member

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    SacredDisorder is correct, vacuum gauges are helpful. You can diagnose the condition of your engine. If you know the engine pulls a specific amount of vacuum at idle and things change you know you have a problem. If the needle is bouncing around you might have a burnt valve or bad rings. Then you know you need to do a compression test. You can see how the bypass valve is working, and tell the difference when you install a Detroit Tune bypass valve. You can know to look for a leak in a vacuum line if the reading goes down from normal.
     
  10. Nathan

    Nathan Founder

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    Yes, there should be a vacuum side to the gauge.
     
  11. CHKMINI

    CHKMINI Club Coordinator
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    Dave, who's gauge is that. I like the face because it matches close to the JCW gauge faces.
     
  12. Kellen@Craven

    Kellen@Craven New Member
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    Okay, so looking at that X-Line gauge that Dave.0 posted. It shows +/-30 with a lot more real estate being granted to the boost. Looks like about half the face. It seems that most of you feel like the vac side is important, are you happy with 1/4 of the gauge being used for accurate vac readings? Would 1/2 the gauge allow enough movement on the boost side to allow you to be able to quickly tell what the reading was?
     
  13. Mr. Jim

    Mr. Jim Mudshark
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    I have the stock boost gauge and its half the gauge with zero at 12 o'clock. Either way the your only using 1/2 to 3/4 of both sides. You'll never hit 30" vacuum, lets hope not and never full numbered boost.
     
  14. CHKMINI

    CHKMINI Club Coordinator
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    Personally I like the look of Dave.O's X-Line gauge and also like the dark face that matches the JCW dark gauge faces.
     
  15. Metalman

    Metalman Well-Known Member
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    Vacuum info is great to have but I feel it's important to show more sweep on the boost side to better see smaller increments of boost...
     
  16. Kellen@Craven

    Kellen@Craven New Member
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    So, if it were up to you metalman, you'd have the gauge use just a little space to show vacuum on a reduced scale. Thus, leaving most of the gauge to show fine increments of boost. Still reading from 30 to 30 like that X-Line?
     
  17. DneprDave

    DneprDave Well-Known Member
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    I use the vacuum part of my boost gauge, when I'm trying for maximum miles per gallon.

    If I keep the gauge in maximum vacuum for conditions, the mileage goes way up.

    Dave
     
  18. anuppercasej

    anuppercasej New Member

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    I think it should show vacuum as well. I like seeing the gauge be a little more active.
     
  19. Dave.0

    Dave.0 Helix & RMW Powered
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    Yeeeeeah I only see vacuum when stopped.:devil::lol::Thumbsup:
     
  20. Metalman

    Metalman Well-Known Member
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    Yep...
     

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