Boost/AFR gauge - Engine Off, On, and negative readings

    Ok, have a question for you all. Hooked up the PSB-1 boost/AFR gauge from Innovate today and I'm curious about something. I totally get how when the engine is running it's measuring the vacuum and it's negative -12 to -15 etc... Gas it and you can get it to zero. Assuming when I get this on the street and under load we'll see the boost being made. My question though is why would there be negative boost with the engine off? I even unhooked it from the boost line and just left to atmosphere and it's the same -6.2.


    Is this normal? Why doesn't it read zero when the engine is off? I went through manual a few times and the only calibration I saw was for the o2 sensor. Just wondering if there is something I'm missing that maybe you guys are aware of before I reach out to innovate and ask. Thanks guys.

    From - https://www.clubwrx.net/thread…-read-negative.134321099/ -

    "

    If the turbo is not forcing air into the engine, the engine is sucking air which is what causes vaccuum. A negative reading on a boost gauge is meerely telling you how much vaccuum your engine is pulling.



    Don't call it negative boost though..."


    The negative sign simply indicates vacuum as opposed to boost.

    I'm learning.


    I've been watching some videos and get why the vacuum is there with engine running, but not sure why still negative (-6.2) with engine off and/or that hose to atmosphere. I think it's setting though as on others when engine on it shows 0psi and not that negative reading.

    Quote from 3GunSteve

    I'm learning.


    I've been watching some videos and get why the vacuum is there with engine running, but not sure why still negative (-6.2) with engine off and/or that hose to atmosphere. I think it's setting though as on others when engine on it shows 0psi and not that negative reading.

    My Innovate SCG-1 shows 0 psi before I start the motor.

    Edited once, last by BKL ().

    Quote from 3GunSteve

    Ok, have a question for you all. Hooked up the PSB-1 boost/AFR gauge from Innovate today and I'm curious about something. I totally get how when the engine is running it's measuring the vacuum and it's negative -12 to -15 etc... Gas it and you can get it to zero. Assuming when I get this on the street and under load we'll see the boost being made. My question though is why would there be negative boost with the engine off? I even unhooked it from the boost line and just left to atmosphere and it's the same -6.2.


    Is this normal? Why doesn't it read zero when the engine is off? I went through manual a few times and the only calibration I saw was for the o2 sensor. Just wondering if there is something I'm missing that maybe you guys are aware of before I reach out to innovate and ask. Thanks guys.

    From what I have gathered, you are in Colorado and at altitude, so your base pressure will be lower than standard pressure and the reason you are seeing a negative number with the engine off but keyed up. What altitude are you at?