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  1. #1
    b_dolla44's Avatar
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    Unhappy How many lbs of Vacuum do you have at idle???

    So I just got done swapping my Riva gen 1 IC out for a XS type 3 IC. I also installed a Jlewis gauge pod(), and a AutoMeter Phamton boost gauge.
    I fired it up, and I'm only seeing 10lbs of vacuum at idle....
    This seems low...
    But I only let it run for 15 secs or so....
    My question is...
    A). How many lbs of vacuum do you see at idle?
    B). Is there a idle air control valve?(if so, that would explain the low vacuum)
    C).If there is a idle air control valve. How long does it take to close????


  2. #2
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    Only 10 lbs. I've never seen more than 4-5 lbs. vacuum at idle... on a digital dynotune gauge.

  3. #3
    b_dolla44's Avatar
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    Quote Originally Posted by BigDaddyRXP View Post
    Only 10 lbs. I've never seen more than 4-5 lbs. vacuum at idle... on a digital dynotune gauge.
    WHEW!!!What a sigh of relief.... I was used to my Turbo/NA drag car engines. (25-35)lbs of vacuum....

  4. #4

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    I see around 10 in/hg as well

  5. #5
    Norwegian Wiking Trond's Avatar
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    Quote Originally Posted by b_dolla44 View Post
    WHEW!!!What a sigh of relief.... I was used to my Turbo/NA drag car engines. (25-35)lbs of vacuum....
    Hmmmmm.... If you see more than 14,7psi of vacuum, then you have broken the law of fysics!!
    Its not possible to have any lower than 0 bar (-14,7psi).... the atmosphere is 1 bar (14,7psi).

  6. #6
    R88ory RXP's Avatar
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    Quote Originally Posted by b_dolla44 View Post
    WHEW!!!What a sigh of relief.... I was used to my Turbo/NA drag car engines. (25-35)lbs of vacuum....
    vacume is measured in IN/HG not PSI

    R88

  7. #7
    Vern's Avatar
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    This is a good question and can indicate a number of issues with a motor ... after I got my cam timing right, I am seeing 11 - 13 inches of vacuum at idle. I wish I would have checked vacuum when I was off a tooth, but I suspect it would have been much lower. I would like to hear what others measure on their skis too ...

  8. #8
    Moderator Snoman's Avatar
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    My ski i am seeing 10 on an autometer mechanical guage..On my wifes i am seeing 7.5-8 with a dynotune guage

  9. #9
    b_dolla44's Avatar
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    Quote Originally Posted by Vern View Post
    This is a good question and can indicate a number of issues with a motor ... after I got my cam timing right, I am seeing 11 - 13 inches of vacuum at idle. I wish I would have checked vacuum when I was off a tooth, but I suspect it would have been much lower. I would like to hear what others measure on their skis too ...
    Vern,
    I remember back in the day when I used to play with turbo Honda's (B series) If you had a "low mile" well taken care of B series it would make "30ish" inch's of vacuum...
    I remember making a test run at the strip. When I hit 4th gear I looked over at the boost guage to see that it was buried in the 30+lbs of boost......(car was only tuned to 15lbs)..By the time I realized i had a major problem it was to late... The Tial wastgate I was running had a Ebay diaphragm in it and broke...causing a huge boost spike... When I let out of it, and got the stopped I looked back over at the boost gauge to see that it wasn't making any vacuum at all...(oops)...Long story short. Vacuum can be a great tool when checking for problems....

  10. #10
    Vern's Avatar
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    Ouch! That would not be a good day! Zero vacuum = expensive repairs ... bummer.

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