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Thread: MAP AE messing with part throttle fueling.

  1. #1

    Default MAP AE messing with part throttle fueling.

    Hello Guys. I'm having an issue with what I believe is the MAP Acceleration Enrichment table adding fuel during low RPM/light throttle conditions. This happens between 1200 to 1800ish RPM. My lbs/hr per the fuel map vs. actual injected amount is different, and CL Comp creeps up to -50%. I had this issue at idle when I first installed the Sniper, but was able to take care of it by increasing the Blanking value. Problem here is, by the time I increase the Blanking value enough to where I'm not seeing any little movement on the enrichment graph (while watching it run with the laptop) acceleration is horrible, it completely falls on its face. I tried making up the difference with a more aggressive TPS AE graph to no avail. Is there some other way around this? Also, is there a way to check to see what's effecting your actual fuel injected vs. Base Fuel Table amount to make sure the MAP table is the culprit? Even with the Blanking value increased, I'm still seeing a difference between base fuel and actual fuel injected, although the difference is smaller. Thanks, Jason

  2. #2
    Join Date
    Feb 2020
    Wheeling, WV


    There are lot's of workarounds, but sometimes you're just hand cuffed by the design of a throttle body and speed density fueling calculations.

    First thought, what's your engine package and specifications? Could be you'll need to run it in Open Loop until 1500 to 1800 RPM if you have a lot of overlap of the valve events.
    Second thought, if it feels correct and performs correct with a low MAP AE Blanking value you could limit the CL Comp to in the neighborhood of -5% below 2000 RPM. I'm curious, what are your Blanking values now and after you changed them?

    Third, after you raise the MAP AE Blanking value you mentioned the acceleration is not good. What type of acceleration? What MAP range, TPS Rate of Change, TPS position start & end, RPM start & end?

    Fourth, it sounds to me like you may be relying on the MAP AE to do too much of the work during AE. Have you looked through all the options/AE modifier tables you have? There's a lot of adjustment there and the MAP is generally relied on the least for AE. You may be overlooking the AE Correction vs TPS and potentially the temperature modifier tables.

    Are you sure your Base Fuel Table is well tuned? That needs to happen before the AE tuning happens.
    I'm doing a lot of guessing here, so if you'd like to download your GCF from the ECU along with a datalog of the occurrence we'll take a look.

    On to your second question. I haven't dug into the EFI software deep enough to see if there's an easy way to show all that's calculated to come up with a final lb/hr that you are seeing on your data screen, but the long way around is to do the math yourself. You have to start with the Base Fuel Table, then Learn Table, then CL Comp, then all the temperature modifiers, and then all of the AE modifiers. Pay attention when you're doing your math as some of the modifiers are in lb/hr and not percentages of the Base Fuel Table.

  3. #3
    Join Date
    Nov 2014
    Ont. Canada


    The first thing you should do when any issues arise is to datalog the event. All the info is there.

  4. #4
    Join Date
    Dec 2009


    Quote Originally Posted by a b c View Post
    Are you sure your Base Fuel Table is well tuned? That needs to happen before the AE tuning happens.
    This is usually the problem, or the engine doesn’t like the Target Air/Fuel Ratio table in that area. (EFI Acceleration Enrichment In Carburetion Terms)

    Originally Posted by Danny Cabral
    The Target Air/Fuel Ratio Table & Base Fuel/Timing Table (and MAP kPa & RPM axes/scales) should be configured using the Sniper EFI software: In the Sniper EFI software (LINK), Target Air/Fuel Ratio Table (Fuel ICF) & Base Timing Table (Spark ICF), select "2D Table" Type (not "Simple"). The Target Air/Fuel Ratio Table & Base Timing Table can then be properly configured & tuned for any engine. I always suggest taking notes of your current distributor's ignition timing specs/curves beforehand, and then program the Base Timing Table accordingly. (Sniper EFI Software & Holley 558-443 CAN/USB Dongle) (Sniper EFI Optional Comm/Data Cable Accessories)

    Quote Originally Posted by 81 TransAm View Post
    The first thing you should do when any issues arise is to datalog the event. All the info is there.
    Overlay the datalog onto your Config File, and 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). (Holley EFI Datalogger Instructions) (Datalog Information - Read "NOTES") (How To Record & Email A Datalog) (Closed Loop Datalog Tuning - Posts #2, #4 & #6) (Holley Sniper EFI Datalogging Tech Video)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 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, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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 & 245/45R17 M/T Street Comp tires.

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