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turbo surge and blow off valve

Discussion in 'Forced Induction' started by b16coupe, Aug 25, 2004.

  1. b16coupe

    b16coupe Senior Member

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    I have noticed when i shift i hear a "che-che-che-che" sound that sounds like it is coming from the driver's side of the enginge bay, but this is when I am not making any boost. Whenever I shift and the there is 2-5 psi, I can hear the same "che-che-che" with the "sssssss" that the BOV makes. When I lift my hood and rev the motor a little, I can see the bov opening up but I cant hear anything, so i know that it works without makeing any boost.

    Isnt that che-che-che sound turbo surge? and why is it happening if my bov is working? Could i be building up a lot of pressure between the turbo and intercooler that would make it surge?

    Thanks
     
  2. pissedoffsol

    pissedoffsol RETIRED

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    sounds like surge to me....

    where is yoru BOV mounted?
    what kind?
    is it one that requires tuning/strength?
     
  3. b16coupe

    b16coupe Senior Member

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    It is mounted about 7 inches off of the TB.
    It is a 45 dollar ebay bov. looks kinda like the turboxs kind but is shorter.
    It has a twistable head on it for soft and hard settings and right now it is set pretty far into the soft area.
     
  4. [Freemantle]

    [Freemantle] Senior Member

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    Just because the BOV is opening does not mean that you are sufficently relieving pressure. That valve may have a restriction in it that would make the air flow a lot less than it appears. I'm not saying it is "crap becase it is from ebay", but it is a definate possibility. 7 inches is kind of close to the throttle plate. Though the "surge" travels downstream from your shut throttle plate, there is a point where it is too close. I'm sure there is a thermodynamic reason for this that I'm not educated enough to explain, but it probably has to do with the immediate reversal in flow energy creating too much turbulence in the area near the plate, making it hard to force air in any direction.

    Worse case scenario you need a new charge pipe and BOV. The BOV is simply too restrictive/misplaced.

    Best case scenario, the BOV is trying to mimic the HKS noise and it is perfectly fine. If it isn't the HKS-style "reversed" BOV we can rule out that possibility.
     
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