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EFI Newbie here, ? on closed loop mode

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  • EFI Newbie here, ? on closed loop mode

    I've only gotten into fuel injection in the last couple months. I had no idea this forum existed when I did my install, it would have made life easier!

    I'm running a moderate 392 with a Howell TBI setup (bought used) on a squarebore intake, intank GM fuel-pump in the stock Scout tank, and fuel pressure and mixture gauges.

    The guy I bought the setup from advised me to let the engine warm up and go into closed loop mode before adjusting the timing (not controlled by the ECM, yet...) and idle speed. Other than waiting until full temp. is reached on the engine temp. gauge, how can I know when the engine has switched from closed to open loop operation?

  • #2
    Re: EFI Newbie here, ? on closed loop mode

    Originally posted by Zane Z
    I've only gotten into fuel injection in the last couple months. I had no idea this forum existed when I did my install, it would have made life easier!

    I'm running a moderate 392 with a Howell TBI setup (bought used) on a squarebore intake, intank GM fuel-pump in the stock Scout tank, and fuel pressure and mixture gauges.

    The guy I bought the setup from advised me to let the engine warm up and go into closed loop mode before adjusting the timing (not controlled by the ECM, yet...) and idle speed. Other than waiting until full temp. is reached on the engine temp. gauge, how can I know when the engine has switched from closed to open loop operation?

    If you don't have a way to monitor the sensors IE: laptop, afr meter, volt meter on the O2 sensor. I'm not sure how you would.
    If you can watch the readings on the O2 sensor you will know you are closed loop when the voltage swings from about .6 volts down to .03 volts + or -. The ECM has to vary the AFR to keep the cat operating properly so it make very small changes which causes the O2 readings to fluctuate up and down while in closed loop.
    If you build/buy a cable and run winaldl on a laptop it will tell you when you are closed loop by the closed loop flag being set.

    HTH
    Bill USN-1

    COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
    HAMILTON FUEL INJECTION
    May be the answer to all your fuel injection needs!
    Learn to do it right.

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    • #3
      Thanks. It shouldn't be hard to measure voltage from the O2 sensor, I'll give it a try.

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