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Thread: Holley Pro-jection problem

  1. 26th February 2010, 08:24 AM #1
    blu77
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    Holley Pro-jection problem

    Hi guys

    is there anyone using this system/know about tuning?

    i cant tune the idle mixture back enough to pass NSW's emissions, that is it runs way too rich under say 2500 revs (more than twice leagal limit!!)

    do you think 670cfm is too big for a 4.4L (was lead to believe it was a 5.0L - it might still be.....) or could it just be that the Holley Pro-jection is not suitable

    Thanks
    Tony
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  2. 26th February 2010, 08:27 AM #2
    PhilipA
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    AFAIK the Holley projection is too big for a 4.4.

    The injectors have a high flow rate which cannot be adequately controlled at the low air demand at idle.

    AFAIR the total air demand of a 3.9 is less than 350 CFM at full throttle, and the projection is something like 670-750CFM.

    Regards Philip A
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  3. 26th February 2010, 10:44 AM #3
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    bee utey
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    Quote Originally Posted by blu77 View Post
    Hi guys

    is there anyone using this system/know about tuning?

    i cant tune the idle mixture back enough to pass NSW's emissions, that is it runs way too rich under say 2500 revs (more than twice leagal limit!!)

    do you think 670cfm is too big for a 4.4L (was lead to believe it was a 5.0L - it might still be.....) or could it just be that the Holley Pro-jection is not suitable

    Thanks
    Tony
    Try an adjustable pressure regulator on the fuel rail, adjust the pressure down to get your emissions to spec. It's quick! otherwise smaller injectors.
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  4. 26th February 2010, 08:32 PM #4
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    Blknight.aus
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    Quote Originally Posted by bee utey View Post
    Try an adjustable pressure regulator on the fuel rail, adjust the pressure down to get your emissions to spec. It's quick! otherwise smaller injectors.
    seconded... however run the pressure too low and your injectors will dribble and you'll get crappy running when cold.
    Dave

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  5. 28th February 2010, 02:11 PM #5
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    Quote Originally Posted by blu77 View Post
    Hi guys

    is there anyone using this system/know about tuning?

    i cant tune the idle mixture back enough to pass NSW's emissions, that is it runs way too rich under say 2500 revs (more than twice leagal limit!!)

    do you think 670cfm is too big for a 4.4L (was lead to believe it was a 5.0L - it might still be.....) or could it just be that the Holley Pro-jection is not suitable

    Thanks
    Tony
    670cfm is at least twice the size you need, Regards Frank.
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  6. 1st March 2010, 11:42 AM #6
    PhilipA
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    I am assuming the Pro-jection that you have is a 670CFM unit it is a throttle body injection TBI with 2 barrels and two injectors which replaces a two barrel carby.

    AFAIR the fuel pressure on these is not 2.5 ATM like a port injection unit but a lower pressure anyway.

    The problem AFAIK is that the gas velocity on a smaller engine is quite low and gives an unreliable signal to the ECU to provide a reliable idle and that the injectors are too large to be able to reliably provide a small enough shot to get the correct idle mixture.

    In other words the unit is too large for your motor.

    I cannot see that an adjustable Fuel pressure regulator will work or that smaller injectors will work.

    When I fitted "Federal " injection to my 3.5 about 15 years ago, that is why I rejected Holley Pro-Jection as an option.

    Looking at the Holley site They apparently do a single barrel that could work, but I assume you bought an old one second hand.
    Regards Philip A
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