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OBA artificial high idle ideas?

Discussion in 'The Garage' started by southernspeed, Sep 15, 2006.

  1. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Those of you running OBA. How do you keep a high idle when using air? I've just finished my set up and it seems to need around 1500rpm to keep a constant pressure when using air tools etc.
    Does any one use high idle solonoids? Choke cables?
    Pictures and ideas please! This is on a TBI and I've considered using the A/C command high idle but I don't think it's enough (although I could programme it higher but then I'd also have a too high idle when driving with A/C on).

    Any thoughts?
     
  2. cbbr

    cbbr 1 ton status GMOTM Winner

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    I shove my mag light in on the gas pedal. Low tech, but cheap and functional.
     
  3. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Cheap b*tch!:D . I was kind of looking for something a bit more technical but I can see where your coming from!:D
     
  4. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    The lowest tech , easiest tech would seem to me a manual choke cable , a homemade bracket , and make it attach to the throttle lever somehow like drill an extra hole or something :dunno:

    therobzilla has a higher tech little box that he can dial a knob and set his idle anywhere he wants .
     
  5. cbbr

    cbbr 1 ton status GMOTM Winner

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    I didn't think that there was any lower tech way than a maglight.:D
     
  6. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    The maglight has batteries , so its disqualified :wink1:
     
  7. Slapperbar

    Slapperbar Retired Navy NDT Examiner Premium Member

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    A brick is low tech. A rock is lower. Neeyah. THHWWPPPP!!!!
     
  8. Slapperbar

    Slapperbar Retired Navy NDT Examiner Premium Member

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    You could use a PTO hand throttle w/a lock on it.
     
  9. Emmettology 101

    Emmettology 101 3/4 ton status

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    Our kenworth had a choke type pull knob in it to set idle. You would pull it out and it would click and stay, the idle would go up some.. Then you could turn the knob to adjust the idle.. Pretty cool idea and set-up... To release it, you would push a button in the middle of the knob.
     
  10. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    Carburetors have the little solenoid that kicks up against the throttle return when the A/C compressor kicks on. That's why it idles faster when the A/C is on. Don't know about a FI system, but if it's done electronically on a FI use the carb solenoid to a on off switch to activate it or if the FI uses the same solenoid, use a switch to activate that one...........my $.02 worth.......oops........that would be a pence worth......maybe.....? :D
     
  11. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Penneth worth, or with inflation, tuppence worth!:D
    The FI uses the ECU to raise it. I was thinking of a solonoid. I'll have to try to find something to mock up. It's not the sort of thing you see over here much a junk yards!
     
  12. 1979jimmy350

    1979jimmy350 1/2 ton status

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    you might want to look in to your ecm code, if you have a empty input pin on your ecm you could write a patch that when you close a circut it bumps up the idle to a specified parameter, Some cars used a PS pump switch that would bump up the idle under load, if you could find code like that for your ecm that would be the best
     
  13. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Interesting idea. A bit out of my league I think. I can burn a programme but as for finding pins for certain jobs......?
    If anyone can throw some light on this for a 7747 ecm??
     
  14. the beast

    the beast 1/2 ton status

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    I've yet to figure out the system (course haven't really looked either) but typically an ambulance or two truck has a high idle switch that will trip a solenoid to bring up the RPM's while parked and working. Granted those are usually on diesels, but I'm betting a similar set-up could work on a gas motor.
     
  15. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    I would say hook up the AC wire from ECM 7747 for idle up. Mine kicks it up to 1000 when in use. Wired switch just for idle up " Helps when winching too". If rpms are not high enough reburn your chip and have it set to your wishes. If your OBA is not holding psi is your check valve working ?
     
  16. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    If I've got an extra one or they're your price at the Auto Parts Store, I'll send ya one if ya want to do that.
     
  17. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    PM'd ya.:D
     
  18. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    As I say though, I don't want a really high idle while driving with the A/C on. It is holding pressure but can't maintain a good pressure at idle while using air tools. It can though at 1200+ rpm.
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    Only problem I see with using those solenoids on a TBI is getting them to bolt up somehow. I guarantee its possible, but not sure how easy it will be.

    I would look into the '747 a bit deeper. There may be a fan routine already there for the cars. (can't recall if TBI F-bodies used an electric fan, I think yes) I know on the '165 ECM there is a "fan anticipate" routine, which basically compensates for the additional load the alternator is about to exert on the engine.

    Another option might be provisions for a power steering switch. I believe that again the '165 has this as well, but with TBI cars, may have also been in use.

    Yet one more option MIGHT be to go with a different ECM entirely, one that is later and has exactly what you need. A bit more complex, but doing all that stuff automatically through an ECM you tuned is infinitely cooler than mechanical stuff. Since it is possibly already available, why not? :)

    If you haven't already, you might spend some time on the diy-efi.org gmecm FTP section, they have many pinouts and what not. If no satisfaction with the '747, start looking around at later TBI ECM's, and see what THEIR pinouts and code have possible.

    There is a "bcc find" tool out there, I can't recall what the site is now, but you can use it to find different ECM's and what not, so you could search thirdgen and gmecm with the ECM number that is a possibility.
     
  20. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Thanks for your thoughts Dorian. Dontoe is sorting me out a solonoid which will work for now if I can set it up properly. I'll look into to higher rpm commands, which, although is beyond my ECM knowledge at the moment, is certainly the best way to go.
    Time to do some more online reading I guess!
     

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