Results 1 to 15 of 15
  1. #1
    14 PSI Boost Cellos86SVO's Avatar
    Join Date
    Sep 2007
    Location
    Redondo Beach/Santa Cruz, CA
    Posts
    64
    SVO's: 1986 SVO

    Off idle bogging, pulls timing at upper rpms, post installation of new parts

    Hey guys,

    So I recently made some major revisions to the engine in the form of:

    -a rebuilt turbo from Charlie
    -a gnari manifold
    -3" downpipe
    -partial removal of the A/C system (compressor and lines to and from evaporator have been removed)

    Other items replaced:

    -O2 sensor (w/ new NGK O2 sensor from rockauto)
    -EGR tube

    Everything went back together mostly OK (apart from having to fab up new coolant lines, oil lines, and the downpipe).

    Now the not so fun part: the car starts up no problem and idles fine, but it bogs just off idle but then steadies at around 1500 rpm and revs fine to red line. Driving it around is the same story but as soon it starts building boost at around 8-9psi, it pulls timing. I pulled codes and got: 18 for KOEO and 47 for KOER. I also tried disconnecting the knock sensor to see if it would change anything, the result was that the off idle bogging went away. (My suspicion is that the coolant tube that goes behind the block is hitting the EGR tube and potentially triggering a false knock signal, I would actually like to remove this hard line and replace it with a soft line or remove it all together if possible.) However, when I drove it around the block with the sensor unplugged, the ECU was still pulling timing at 8-9 psi.

    I would really like to run a Pimp ecu on this car but I want to try and get the car running with the original ecu before I dive down that rabbit hole.
    1986 Mustang SVO
    1988 Mustang GT 'vert

  2. #2
    OVER-BOOST!! GAboySVO's Avatar
    Join Date
    Dec 2002
    Location
    Acworth, GA
    Posts
    3,200
    SVO's: 2 - 9Ls
    Have you verified your fuel pressure? Base timing? TPS voltage and base idle?
    Mike S

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

  3. #3
    14 PSI Boost Cellos86SVO's Avatar
    Join Date
    Sep 2007
    Location
    Redondo Beach/Santa Cruz, CA
    Posts
    64
    SVO's: 1986 SVO
    I forgot to add that I checked the base timing and it is at 10*. I'll check base fuel pressure and TPS voltage.
    1986 Mustang SVO
    1988 Mustang GT 'vert

  4. #4
    Max BOOST! SchoolBoy's Avatar
    Join Date
    Oct 2007
    Location
    Arlington Wa
    Posts
    465
    SVO's: 85 SVO Canyon Red
    With adding all this free flowing exhaust did you readjust your boost level and it should be making alot more now creating a overboost situation.
    85 SVO 2A 205rwhp & 266 pounds torque!
    SDS Found, FMIC Built, Dash pad triple gauge pod

  5. #5
    Administrator SVOeric's Avatar
    Join Date
    Mar 2002
    Location
    Richmond, KY
    Posts
    12,719
    SVO's: 86-1C & 86-1E
    Quote Originally Posted by Cellos86SVO View Post
    I forgot to add that I checked the base timing and it is at 10*. I'll check base fuel pressure and TPS voltage.
    You say timing, just have to make sure, cause I've seen it before....
    Ignition timing is at 10 deg.
    cam timing, should be at ZERO. (assuming stock CAM)

    Another item that will cause an SVO to fall on it's face-- does the hose that runs between the turbo and the VAM have the spring in it, to keep it from collapsing?
    Eric C
    SVOCA Webmaster

  6. #6
    14 PSI Boost Cellos86SVO's Avatar
    Join Date
    Sep 2007
    Location
    Redondo Beach/Santa Cruz, CA
    Posts
    64
    SVO's: 1986 SVO
    Quote Originally Posted by SVOeric View Post
    Another item that will cause an SVO to fall on it's face-- does the hose that runs between the turbo and the VAM have the spring in it, to keep it from collapsing?
    Bingo. Spring was missing, I don't regularly run the car with this hose except for when it gets smog'd and everything has to look stock. I put on the usual silicone hose and couplers that I usually run and now everything seems to be good.
    1986 Mustang SVO
    1988 Mustang GT 'vert

  7. #7
    14 PSI Boost Cellos86SVO's Avatar
    Join Date
    Sep 2007
    Location
    Redondo Beach/Santa Cruz, CA
    Posts
    64
    SVO's: 1986 SVO
    So now it appears I have a boost creep problem...

    The car has a Hallman manual boost controller and currently I have it set to the lowest setting. Driving around town it doesn't go above 10 psi, but on the highway in 4th or 5th, the boost starts to climb up to 15-16 psi. I realize this is a common symptom but have I exceeded the limits of the internal waste gate? or is something else going on?
    1986 Mustang SVO
    1988 Mustang GT 'vert

  8. #8
    OVER-BOOST!! GAboySVO's Avatar
    Join Date
    Dec 2002
    Location
    Acworth, GA
    Posts
    3,200
    SVO's: 2 - 9Ls
    Boost creep is due to the wastegate not allowing enough exhaust gas to bypass the turbine wheel to maintain boost. The best way to determine if the issue is the wastegate or the MBC is to remove the boost controller and perform the 4th and 5th gear pulls again. If boost no longer creeps, then the issue it the boost controller. If it still creeps, then the wastegate is not opening completely for some reason. Verify the flapper lever is not binding or there is not a pin hole leak in the WG diaphragm.
    Mike S

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

  9. #9
    14 PSI Boost Cellos86SVO's Avatar
    Join Date
    Sep 2007
    Location
    Redondo Beach/Santa Cruz, CA
    Posts
    64
    SVO's: 1986 SVO
    Sorry for the slow updates, but here's a quick vid of me running a check on the wastegate with a handpump:

    https://youtu.be/C2Q9Srw0sOU
    1986 Mustang SVO
    1988 Mustang GT 'vert

  10. #10
    Administrator SVOeric's Avatar
    Join Date
    Mar 2002
    Location
    Richmond, KY
    Posts
    12,719
    SVO's: 86-1C & 86-1E
    I don't see anything wrong with that.
    Eric C
    SVOCA Webmaster

  11. #11
    OVER-BOOST!! svono50's Avatar
    Join Date
    Apr 2002
    Location
    Streamwood, IL
    Posts
    3,639
    SVO's: 86 1C
    It does seem to operate under the correct pressure. My question, is it really opening up 'enough' or is the stroke limited on the wastegate diaphragm or in the wastegate flapper valve? Anyone have a spec on the stroke length of the diaphragm?
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  12. #12
    14 PSI Boost Cellos86SVO's Avatar
    Join Date
    Sep 2007
    Location
    Redondo Beach/Santa Cruz, CA
    Posts
    64
    SVO's: 1986 SVO
    That's what I'm wondering. Here is a vid with the boost controller bypassed: https://youtu.be/ZNn8UcbMjqA , boost creep is still there.

    I guess since I'm planning to just run 15-16 psi, this should be OK. I'll have to fix it next time I have the turbo off.
    1986 Mustang SVO
    1988 Mustang GT 'vert

  13. #13
    OVER-BOOST!! svono50's Avatar
    Join Date
    Apr 2002
    Location
    Streamwood, IL
    Posts
    3,639
    SVO's: 86 1C
    That certainly looks like a-typical boost creep to me. Not too excessive, but still present. May require some work to the exhaust housing to enlarge the port too. If you are OK living with it till you pull the turbo, I wouldn't worry too much about it, but just don't forget about it!
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  14. #14
    OVER-BOOST!! GAboySVO's Avatar
    Join Date
    Dec 2002
    Location
    Acworth, GA
    Posts
    3,200
    SVO's: 2 - 9Ls
    Quote Originally Posted by Cellos86SVO View Post
    That's what I'm wondering. Here is a vid with the boost controller bypassed: https://youtu.be/ZNn8UcbMjqA , boost creep is still there.

    I guess since I'm planning to just run 15-16 psi, this should be OK. I'll have to fix it next time I have the turbo off.
    You could get boost is the wastegate has a leak. That's what happened to mine. Apply 10psi to the wastegate and hit it with some soapy water.
    Mike S

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

  15. #15
    Administrator SVOeric's Avatar
    Join Date
    Mar 2002
    Location
    Richmond, KY
    Posts
    12,719
    SVO's: 86-1C & 86-1E
    or hit it with 10 PSI, (hand pump) and see how long it holds.
    Eric C
    SVOCA Webmaster

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •