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Thread: Idle AFR keeps going leaner & leaner until engine stalls.

  1. #1
    Join Date
    May 2017
    Location
    Grosse Ile Michigan
    Posts
    11

    Default Idle AFR keeps going leaner & leaner until engine stalls.

    39' offshore Catamaran. Pair of 598 cid with 871 superchargers 1150 HP. Dual Terminators. Engines run great. Problem is engines below 1200 RPM slowly drop off AFR from 12.5 to 18 and engine stalls. If I up the idle to 1500 or above, it does not do it. Hard to dock the boat at 1500 RPM. The AFR set on the table is 11:1, but the engine never goes there. The Learn never comes on at idle. Also, the engines run a 95°F.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,903

    Default

    Quote Originally Posted by janetlaw View Post
    Engines run great. Problem is engines below 1200 RPM slowly drop off AFR from 12.5 to 18 and engine stalls. If I up the idle to 1500 or above, it does not do it. Hard to dock the boat at 1500 RPM.
    You'll have to record & review a datalog of the stalling occurrence. Read center paragraph in blue print:

    Originally Posted by Danny Cabral
    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Global File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).


    I find the most helpful datalog function, is overlaying the datalog on your Global File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Global File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Global File (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    https://forums.holley.com/showthread...s-amp-Datalogs (Datalog & System Log Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    https://www.youtube.com/watch?v=q7OZUXLRS1Q (How To Record A System Log & Diagnose A No-Start Condition)
    https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    The AFR set on the table is 11:1, but the engine never goes there. The Learn never comes on at idle. Also, the engines run a 95°F.
    Closed Loop & Learning happens at all RPM, provided the Closed Loop/Learn Parameters are programmed as such.
    The Coolant Temperature Enrichment % & A/F Ratio Offset tables must be at 100% & zero to enter Learn mode.
    You'll need to reconfigure these tables if you're running the engine colder than what the base calibration specifies.

    The base calibrations only enter Learn mode at 160°F. The ECU enters Closed Loop mode as soon as the WBO2 sensor completes its initial heating cycle.
    Check your Closed Loop/Learn parameters. "Enable Closed Loop" and "Base Fuel Learn Enabled" are the only parameters that need to be check marked.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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