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Thread: Turning off learning and light throttle issues

  1. #1

    Default Turning off learning and light throttle issues


    I am having some issues with the atomic fitted to a customers car.

    The engine is a 427 Windsor, 231/239 @0.050 112LSA hydraulic roller cam with 10:1 comp.

    The fuel system is a return type with regulator running at 50psi.

    Dissy is an MSD Pro billet, locked out with the adjustable button retarded 15 deg.

    Static timing is set to 15 BTDC as per the instructions.

    The atomic is controlling the timing.

    The setup I have is as follows,

    Displacement - 427

    Cylinders - 8

    Cam Type - Performance

    Pump Type - Non PWM with regulator

    Air Pump Equiped - NO

    Idle Target - 850

    Rev Limit - 6700

    Timing control - Enabled

    A/F targets - Idle - 13.8, Cruise - 14.6, WOT - 12.8

    Timing - Idle RPM - 950, Total RPM - 3000, Idle Advance - 12, Total Advance - 26, Vac Advance - 12, Vac Type - Unported

    Pump Squirt - 20% Power Valve Enrich - 18%

    Firmware - Dash - 2.0.7, ECU - 1.2.10, Power Module - 1.0.9

    The issues are around very light throttle (under 5%). It goes very lean and the engine stumbles.

    Also, the idle keeps changing AFR. I have set the screws as per the manual, both are open the same amount (about 1 turn). This results is around 10 steps in the IAC.

    Idle AFR when set is as per the target.

    Fuel pressure has been checked, it is stable.

    With the stumble, it's very much like there is a filter that disables the throttle pump below 3 or 4%?

    With the idle, it's like it's learning over the top of itself?

    I have used a lot of different efi systems and they allow for the learn to be disabled in areas of the fuel table once it is set.

    The engine will load up with fuel, particularly getting the car moving or for example, trying to park the car.

    Other than the stumble and the idle, the engine is running ok.

    Any assistance would be appreciated.

  2. #2

    Default Turning off learning and light throttle issues

    The learning cannot be disabled, this system is designed to constantly learn.

    There are a few changes I would recommend based on what you provided.

    The idle AFR is a bit rich, I would bring it back to 14 or so.

    Try a little more initial (idle) timing.

    Allow the total timing to come in a little faster than 3000rpm.

  3. #3

    Default Turning off learning and light throttle issues

    Thanks for your reply.

    Tried the settings suggested and I also spoke to support this morning.

    Tried their suggestions also.

    No real improvement.

    Looking at it a little closer, it appears to be a lean spot in the map.

    Seeing as it is happening in a throttle transition, learning can't happen there due to learning being disabled in transition.

    I guess that I will have to figure out a way to get it to go there in steady state so that it can learn the area.

  4. #4

    Default Turning off learning and light throttle issues

    I also have a Ford 427 W. I learned a few things over the years and if someone does not agree, they will tell.

    Fords like to run a little richer than Chevy's. So, to me your idle AFR is fine. Cruise AFR is too lean. I would suggest to go back to 13.8 or even a bit lower (you have to try for yourself)

    Second: Tming. If your timing is too late you will have some unburned fuel is the exhaust (a lean mixture burns slower than a rich mixture). The sensor will think the engine runs too rich and will try to lean it out even further. Result: a very lean spot. Maybe you did smell some fuel when driving slowly.

    So I would suggest to change your total advance to 30 -34 (just try out what works best for your engine) If the engine starts vibrating you have gone to far with the timing.

    My engine runs best with AFR Cruise is 13.8 and total advane is 34. Together with the vacuum adcance I see an advance of 41 at the highway.

  5. #5

    Default Turning off learning and light throttle issues

    Thanks for the suggestions Ford418W.

  6. #6

    Default Turning off learning and light throttle issues

    I am experiencing the same issue with my 392 Windsor as Lawso01 is. I have a lean condition when very light throttle is applied 1200-2000 RPMs. My AFR goes lean to 16-18 causing a stumble. I have been trying to tune this out with the help from MSD techs and found selecting the Cam Type as "Street" lessened the lean stumble but hasn't eliminated it.

    Here are the specs for my engine and Atomic settings:

    392 Windsor Ford Racing crate engine

    AOD Automatic trans w/2400 stall converter

    355:1 rear gear ratio

    9.7:1 compression ratio

    232/240 @0.050 112LSA hydraulic roller cam

    The fuel system is a return type with regulator set at 48psi.

    MSD billet with centrifugal advance

    Base timing is set to 17 BTDC

    The Atomic setup is as follows:

    Displacement - 392

    Cylinders - 8

    Cam Type - Street

    Pump Type - Non PWM with regulator

    Air Pump Equipped - NO

    Idle Target - 900

    Rev Limit - 6500

    Timing control - Disabled

    A/F targets - Idle - 14.5, Cruise - 13.9, WOT - 12.8

    Pump Squirt - 25% Power Valve Enrich - 19%

    Firmware - Dash - 2.0.7, ECU - 1.2.10, Power Module - 1.0.9

    The issue is experienced under very light throttle (under 5%). It goes lean 16-18 and the engine stumbles. Also, the idle A/F fluctuates more than I would expect. With the A/F set to 14.5 at idle, the actual A/F is 12.8-14.2. The IAC count is about +-5 in gear.

    When Atomic was first setup the Cam Type was set to "Performance" and the stumble was much worse. I changed the Cam Type to "Mild" and the stumble improved considerably. At the advice of the MSD tech, I changed the Cam Type to "Street" with a slight improvement. I have adjusted the Pump Squirt and Power Valve Enrichment with no improvement.

    This past Saturday I reset the Atomic unit with factory defaults. Then I programmed the unit as shown above and drove the car 100 miles. First 50 mile highway driving then 25 miles stop and go. The next 25 miles I tried changing the Pump Squirt, Power Valve Enrichment, and A/F settings for idle and cruise. I adjusted the Idle A/f to 13.8 and Cruise A/F to 13.6 with no change in drivability. The lean condition stumble only got worse.

    Other than the stumble, the engine is running great. I would be completely happy with the system if this issue can be corrected but am growing very frustrated. If this issue can't be corrected, I will be forced to put the carb back on which I really don't want to do.


  7. #7

    Default Turning off learning and light throttle issues


    What timing curve do you have set-up in the distributor?

  8. #8

    Default Turning off learning and light throttle issues

    MSD Atomic EFI Support wrote:


    What timing curve do you have set-up in the distributor?

    I honestly don't know. I believe it is 1000-2500@28* total but I'll have to check with Ford Racing to get the actual information.


  9. #9

    Default Turning off learning and light throttle issues

    I have tried a rich idle to a lean idle, rich cruise to a lean cruise, high idle timing to low idle timing, etc.

    Still no improvement.

    I usually tune multipoint efi, so I am used to finding the issue within the fuel/spark tables and being able to easily correct the issue. In this case, using multipoint, this issue would be caused by a lean area in the base fuel table.

    But, as I mentioned earlier, the ecu is seeing that the throttle is in transition so therefore will not use closed loop or learn.

    As with Bryan, the engine is fine in Idle ( It will however richen up and load up a little at times), cruise and WOT, it's just the transition areas that can't learn.

    I have tried all manor of 'power valve enrichment' and 'throttle pump' settings with no improvement. The only effect will be fuel economy.

    I have even tried as Bryan has, experimenting with different cam type settings hoping that the base fuel table will be richer in the areas I am having issues with. But so far, I have had no real improvement.

    It is frustrating as you can release the clutch and the car will pull away on it's own ( I have even had it go through 1st to 4th gear without throttle!) From this experience, I do not believe there is a timing issue.

    But add just a little throttle and the engine goes very lean ( with 'performace' cam selected the AFR will read 19-20:1 during light throttle transition).

    By changing the cam type to 'Mild', the AFR's will read 16-18:1 in the same situation.

  10. #10

    Default Turning off learning and light throttle issues

    My goal was to let the Atomic EFI control the spark once the tune was finalized. Haven't switched to timing control yet because I felt it may add to the present issue.

    I wish this system had a data logging option. Would really like to see exactly what is going on rather than assuming. When I inquired about data logging during one of my conversations with MSD, they informed me the capability would be available in the future but would require a system upgrade.

    If this problem can't be resolved, I will be forced to remove the EFI system meaning $2600 of wasted money.


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