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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

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    9/06/2018 2:10 PM  #1

    shelb94
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    Registered: 10/01/2013
    Posts: 13

    What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    Should I use an A9L or A9P? I've been collecting parts for years and have purchased a wire harness from Windsor-Fox and have a 5.0 and T5 out of a 1990 Mustang but due to health issues I won't be able to operate a clutch so I'm going to use the C4 auto that is original to the car. Also, are there any other issues that I'll need to address regarding the 5.0/C4 combination? Any help is greatly appreciated!

     

    9/06/2018 6:46 PM  #2

    TKOPerformance
    Hyper FYIFORD ADDICT

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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,530

    Re: What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    The A9L is a manual transmission application; the A9P is for an automatic.  BUT, the automatic assumes its an AOD.  I'm not sure how the ECM will handle not having input from a VSS, and not being able to actuate the converter.  The manual assumes that its a T5, which should have a neutral position switch and a VSS giving it feedback.  I'm sure they can be programmed to skirt those potential problems, if they are indeed a problem.  Those are the things to look out for, but I can't say how they would actually affect anything because I've never run a combination like that.  I know the EECIV well, but my knowledge is limited to Fox Mustang applications, not retrofit applications.  I can say that if you don't get any answers here you should try the EEC forum here:

    https://eectuning.org/forums/index.php?sid=623c29a17cc3ffc807f7ecc8a24ef1a0

     

    9/07/2018 7:45 PM  #3

    Raymond_B
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    From: Fort Worth, TX
    Registered: 4/01/2013
    Posts: 1,213

    Re: What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    This generation of EECs did not control any trans functions. Either will work, I've heard folks say the A9P decels better in an auto (being an auto EEC), but the difference is negligible. Long way of saying whichever one you can find will work with the A9P being a slightly better choice. If you have a tuning device then it truly doesn't matter. 

     

    9/08/2018 3:46 AM  #4

    Hakan
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    From: Långrör, Sandarne, Sweden
    Registered: 4/01/2013
    Posts: 810

    Re: What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    I've used an A9L in combination with a EFI converted old 289 and a C4 without any problems. This was back in 2002 and IIRC I just left out the VSS and neutral switch wiring. Also cut the wires to the fuel injectors and reconnected them to work with the pre'81 firing order, in theory this should not work very well in combination with how the O2 sensor are supposed to work, but in my case the engine ran really well anyway.

     

    9/08/2018 5:26 AM  #5

    Coupedaddy
    I FYI 24-7

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    From: Katy TX
    Registered: 4/18/2013
    Posts: 317

    Re: What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    I done a Fox body4 cylinder to V 8  conversion and the Automatic trans ECM works better in a auto with a Cam. If the cam has a nice lope at idle  you may need a adjustable air by pass valve to get the idle right where it won’t stall or hunt at times at a idle

     

    9/08/2018 6:22 AM  #6

    Bullet Bob
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    From: Montrose, Colorado
    Registered: 4/01/2013
    Posts: 4,892

    Re: What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    As stated, the A9P is better with the auto.  You can use the standard Ford VSS of the period with a modified speedo cable.  This VSS plugs into the trans speedo cable hole and should work on the C4...I think. 

    BB

    "you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
     

    9/08/2018 10:52 AM  #7

    TKOPerformance
    Hyper FYIFORD ADDICT

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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,530

    Re: What eec should I use on my 1965 Mustang with 5.0 efi and C4 auto?

    Coupedaddy wrote:

    I done a Fox body4 cylinder to V 8 conversion and the Automatic trans ECM works better in a auto with a Cam. If the cam has a nice lope at idle you may need a adjustable air by pass valve to get the idle right where it won’t stall or hunt at times at a idle

    Another thing to be aware of is that running an open element air filter in close proximity to the fan can also cause idle instability.  The MAF picks up eddy currents from the fan and causes the engine to surge at idle.  This happens with stone stock engines and modified ones alike. 

    Cam wise you are best running something with a bit wider LSA than would be traditionally thought ideal for a performance cam.  Most cams ground specifically for EFI are on a 110-114 degree LSA.  This reduces overlap and helps preserve a better vacuum signal at idle keeping the MAP sensor signal to the ECM cleaner (less turbulent) and allowing the engine to idle more smoothly. 

     

     

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