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Thread: Lean spike/shutoff - coasting/engine braking.

  1. #1

    Default Lean spike/shutoff - coasting/engine braking.

    I'm having these lean spike issues and have narrowed down my problem after reading a bunch online and searching on here, but I can't quite seem to find the answer. My car is wicked lean on coasting and in particular when using engine braking going downhill. I've actually had it start bucking and then just shut down on hills. I think it might be injection tuning issue that shows up when the car is using throttle engine braking to control speed going downhill. The same thing does happen when I let off the gas for several seconds after cruising on the freeway. I have definitely narrowed it down to those two conditions.

    What I read is the injection systems often cut fuel flow completely I read in these situations both to help the car slow down and to provide some fuel economy savings (“DE” for short). I'm not clear which setting it is, but I already have the Decel Fuel Cutoff already off (box NOT Checked). Are there other settings to solve this lean spike and shutdown issue on coast/downhill engine braking? I also attached my latest Config File. Thanks! 10-21-19 LV2.zip

  2. #2
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    Quote Originally Posted by 8pack View Post
    I'm not clear which setting it is, but I already have the Decel Fuel Cutoff already off (box NOT Checked). Are there other settings to solve this lean spike and shutdown issue on coast/downhill engine braking?
    No, just the Decel Fuel Cutoff.

    Pay special attention to the 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 Config 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 Sniper 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 Config 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 Config File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Config File (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    https://forums.holley.com/showthread...s-amp-Datalogs (Datalog Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    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.

  3. #3
    Join Date
    Nov 2014
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    Ont. Canada
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    Raise your "Minimum Injector Opening Time".

  4. #4

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    It sounds like there are two choices. One is to adjust my Base Fuel Table in the affected cells, and the other is to adjust the Minimum Injector Opening Time (MIOT). I'm having trouble figuring out how to do the fuel table remapping and the associated datalogging, but that might just take some time to figure out.

    Adjusting the affected cells seems more targeted & precise. I assume adjusting the MIOT has an impact across the entire fuel table. That's certainly a quick and easy way if it works, but is it the right way? What are the downsides and impact to the rest of the tune? Thanks!

  5. #5
    Join Date
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    Quote Originally Posted by 8pack View Post
    I'm having trouble figuring out how to do the fuel table remapping and the associated datalogging, but that might just take some time to figure out.
    Read the last LINK in post #2 above.

    Adjusting the affected cells seems more targeted & precise.
    Yes, that's the real problem.

    I assume adjusting the MIOT has an impact across the entire fuel table.
    No, it'll only affect the idle & deceleration areas of the Base Fuel Table.

    That's certainly a quick and easy way if it works, but is it the right way?
    I think it's a Band-Aid fix.

    What are the downsides and impact to the rest of the tune? Thanks!
    Again, the fuel injectors will only be at that low of a pulse-width (msec) at idle & deceleration.
    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.

  6. #6

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    Quote Originally Posted by 81 TransAm View Post
    Raise your "Minimum Injector Opening Time".
    FWIW from Holley Tech Support: "Minimum Injector Opening Time is tied to the dynamic of the fuel injector itself. I would not advise adjusting that unless you literally change the injector itself to something with a different spec."

  7. #7
    Join Date
    Dec 2009
    Location
    Connecticut
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    As I've always stated, tune the Base Fuel Table! The Target Air/Fuel Ratio Table, Base Fuel Table & Base Timing Table are the three most important tables when the engine is running at operating temperature. The Learn Table isn't "tuned" by the end user, it's a self-tuning reference.
    http://forums.holley.com/showthread....7370#post47370 (Closed Loop & Learn Table - Especially posts #2, #6 & #11.)
    http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    http://www.youtube.com/watch?v=qwkqjotkDJQ (Holley EFI Learn/Self-Tuning Demonstration)
    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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