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Thread: Very Lean On Deceleration

  1. #1

    Default Very Lean On Deceleration

    Finished hooking up the Terminator Stealth TBI with Dominator ECU a couple weeks ago and have been driving it around to get through the Learning phase. One thing I've noticed, and that isn't improving, is that the car goes crazy lean on deceleration. Talking about deceleration starting from 70 MPH (fastest I've driven it), and even starting a deceleration from 30 MPH. The handheld shows AFR > 30, and my separate Innovate system caps at 22 (that's all the wideband on that unit is capable of reading). This very learn condition lasts until I either 1) blip the throttle a little, but depending on how much I continue to decelerate, it will go back to very lean again; 2) decelerate all the way back down to idle. This can be over 10 seconds of the lean condition. When I'm decelerating, I have my foot completely off the gas pedal. The AFR doesn't immediately jump to 30+, but it starts creeping up as soon as I take my foot off, and it only takes it a couple of seconds for it to go completely lean.

    I've made sure TPS Position is at 0% when the throttle is not depressed at all. I've done TPS Autosets multiple times just to be certain. I've also made sure to tune the IAC Position to exactly 5% in neutral, after the engine has fully warmed up. I bumped the IAC Hold down to 20%, and that didn't really seem to have any impact.

    Here are my current IAC Ramp Down settings:
    IAC Hold Position: 20%
    IAC Ramp Decay: 4.0 sec
    IAC Ramp Start (RPM Above Idle): 1000 RPM
    IAC Kick: 50%
    I have the IAC Advanced Idle Control set to "Slow" currently. It was set to 4 Bbl TBI, and setting it to slow has had zero impact on the lean deceleration condition.

    Here are the Target AFR settings:
    Idle: 14.0
    Cruise: 14.5
    WOT: 12.5

    One thing that I found in the settings that may be weird, maybe not, is the Minimum Injector Opening Time is set to 0.0. I did not set it that way, the base configuration I loaded had it set this way. I've read other posts where people have this set in the 1.2 to 1.7 range. A few of those posts mentions adjusting this parameter to cure lean deceleration issues. But I wanted to post here first before I touched that value since it came set at 0.0.

    I'm honestly surprised that the engine doesn't cut out at such lean conditions. Would really love to nip this one, as it makes me nervous having the car go that lean every time I decelerate. Thanks in advance.
    Last edited by skizot722; 12-07-2019 at 06:38 PM.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    Default

    This is usually a Base Fuel Table issue.
    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).
    Also, temporarily disable the Decel Fuel Cutoff (Fuel Modifiers - Fuel ICF) until the engine is fully tuned.

    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 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)
    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/3000 RPM converter, FPP aluminum driveshaft, FPP 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 & MT 245/45R17 tires.

  3. #3

    Default

    Thanks, Danny. I can take a look at that and familiarize myself with tuning the Base Fuel Table. Shouldn't the system be capable of keeping things a little bit closer in check? Is the Learning not happening under this condition? Any ideas on my question about Minimum Injector Opening Time being set to 0.0? The Decel Fuel Cutoff is already disabled.
    Last edited by skizot722; 12-09-2019 at 08:30 AM.

  4. #4
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    Default

    Quote Originally Posted by skizot722 View Post
    Shouldn't the system be capable of keeping things a little bit closer in check? Is the Learning not happening under this condition?
    http://forums.holley.com/showthread....5760#post45760 (Scroll down to "Learn Issues, Self-Tuning".)

    Any ideas on my question about Minimum Injector Opening Time being set to 0.0?
    The default setting of 1.00 or 1.20 msec is fine.
    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/3000 RPM converter, FPP aluminum driveshaft, FPP 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 & MT 245/45R17 tires.

  5. #5

    Default

    The default with the base calibration I loaded from the available ones has it set at 0.0, which is why I asked. Should I change it to 1.20 msec?
    Last edited by skizot722; 12-09-2019 at 09:37 AM.

  6. #6
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    Connecticut
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    Default

    Just set it to 1.00 msec (which is what I've always used for small & big blocks).
    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/3000 RPM converter, FPP aluminum driveshaft, FPP 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 & MT 245/45R17 tires.

  7. #7

    Default

    Thanks. I'll have to go back & double-check, but I believe the Learn Gain is set at 150%. Again, this is not a parameter I've adjusted, it came this way in the base calibration I loaded.

  8. #8
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    Connecticut
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    https://forums.holley.com/showthread...0192#post50192 (Related Forum Thread)

    Check all 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/3000 RPM converter, FPP aluminum driveshaft, FPP 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 & MT 245/45R17 tires.

  9. #9

    Default

    Thanks again. Will plan to check these all out soon. What's a bit worrying is that the default values in the base tune I loaded seemed to be fairly off from what they should be, from what I gather reading through the forum. Minimum Injector Opening Time at 0.0, Learn Gain at 150% - just wondering what other values might be bad by default.

  10. #10
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    The maximum Base Fuel Learn Gain is 100%, not 150%. The Minimum Injector Opening Time can be set to zero if you choose to disable it. The base calibrations aren't "wrong" per se.
    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/3000 RPM converter, FPP aluminum driveshaft, FPP 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 & MT 245/45R17 tires.

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