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Thread: No boost

  
  1. #16
    OVER-BOOST!! Bruce's Avatar
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    Did you take just the turbo off or the whole exhaust manifold/header?
    Bruce

  2. #17
    6 PSI Boost
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    Quote Originally Posted by Bruce View Post
    Did you take just the turbo off or the whole exhaust manifold/header?
    I took the exhaust manifold off as well.

  3. #18
    6 PSI Boost
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    Ok, I've got everything back together and the car is running. I went for a little test drive and was only making 8 lbs of boost. After a short while it dropped to only 1-2 lbs. There is a tag on the boost controller hoses that says "don't change the length or diameter or the world will end" is this critical or is it like the tag on a mattress? The hoses were quite worn so I snipped off about 3/8" from each but didn't have a chance to take it for a ride after I did that.

  4. #19
    OVER-BOOST!! GAboySVO's Avatar
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    Don't pay attention to that note. The biggest thing is that you want a hose that transfers boost pressure with little expansion and as quick as possible to avoid over boost. When a manual boost controller is deployed, you have to change the hose lengths to accommodate mounting. Cutting off the end of your existing hose did not cause your issue.

    My guess is that the flapper is stuck open somehow.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  5. #20
    OVER-BOOST!! svono50's Avatar
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    Could be a mucked up spring in the wastegate actuator letting the wastegate be pushed open? Do you have a hand vacuum/pressure pump to verify the actuator and hoses? The stock wastegate, if directly connected to the boost signal, will give you 10 lbs of boost for reference.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  6. #21
    6 PSI Boost
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    I swapped in a brand new wastegate actuator so that’s not the issue. What I did find though is that it blew out the gasket between the header and the turbo. Based on how it ran and how long it took to run poorly I am sure this is the problem. I believe that the new turbo was done by Evergreen but I have no idea what brand the header is.

  7. #22
    Administrator SVOeric's Avatar
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    don't put a gasket between header and head. (you may not have, just pointing it out)
    the turbo and exhaust manifold need to be 'very true' to seal up.
    Eric C
    SVOCA Webmaster

  8. #23
    OVER-BOOST!! svono50's Avatar
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    You used the beaded metal gasket for the header to turbo flange? For that to 'blow out' means that the surfaces are not remaining true to each other. Wonder if that header flange is warping under heat/pressure and unloading the gasket, which would cause a leak and then failure of that gasket. Most tubular headers for our cars seem to be more problematic than not, since the builders typically follow 'normal' header design, which doesn't hold up well with a turbo hanging off of them.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  9. #24
    OVER-BOOST!! gbeaird's Avatar
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    Quote Originally Posted by Paul Gagnon View Post
    <SNIP>I believe that the new turbo was done by Evergreen but I have no idea what brand the header is.
    Picture?
    Gene Beaird,
    86 2R SVO, G Stock,
    Pearland, Texas

  10. #25
    OVER-BOOST!! MIKESVO's Avatar
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    As Ted mentioned, the headers tend to be problematic. Might be best to switch back to a E6 exhaust manifold.
    PETRO EXPRESS=CITGO=BOYCOTT / Illinois - Taxation w/o Representation!

  11. #26
    6 PSI Boost
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    I finally had a chance to get everything back together today. The car is running well now but it will only make 10 psi of boost. The boost comes on quickly and strong but does not climb past 10. Everything is plugged in correctly. I am thinking that the boost controller might be the issue though, especially since I have disturbed a bunch of stuff that hasn’t been touched in 36 years. Any ideas? The weather is going to turn by the end of the week so I may have to leave it until spring.

  12. #27
    12 PSI Boost spt87a's Avatar
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    If its the factory boost controller make sure the vacuum lines to it are not reversed.

  13. #28
    OVER-BOOST!! svono50's Avatar
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    If you plumb directly to the actuator it will limit to 10psi, the controller is what allows boost to climb past 10 psi. As spt87a noted, reverse the lines and see what you get.

    Another test would be to disconnect the actuator from any vacuum/boost signal and see if you can get over 10 psi. **If you do this method, there is NO control on the boost level and it is ONLY controlled by your right foot, so you have to be very careful!!** This method confirms that the actuator is still holding the wastegate flapper closed under higher boost conditions with enough preload.

    Good luck and let us know what you find.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  14. #29
    6 PSI Boost
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    Well, I have figured it out.

    I took the car for a boot last night for the first time since my last post here. After bypassing the boost controller the problem was still there. I mulled it over in my head and it occurred to me that it was possibly the t-fitting on the pressure side since everything else was correct and seemed to be functioning properly. This afternoon I took a look at the t-fitting on the old turbo, lo and behold it was different than the one on the new turbo. I swapped the old one on and my full boost returned. Pretty frustrating but I am glad it was a cheap fix. I wonít forget to make sure that fitting is correct again.

  15. #30
    OVER-BOOST!! svono50's Avatar
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    Glad to hear you finally figured out the issue. It is amazing how some of those small details will foul things up. The factory fitting has an orifice in one of the ports if I remember correctly and I have seen folks swap the hoses on the nipples and foul up their boost levels.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

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