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Thread: IAC settings for Holley TBI

  1. #1
    Carb and Points!
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    IAC settings for Holley TBI

    I am looking for some info on if/when to adjust the IAC settings for my SBC 350. I have a Holley TBI unit where with the larger size figured a change would be appropriate from the stock settings? Part of my reasoning behind this is when I take my foot off the throttle when coming up to a stop the engine takes it's time getting back down to idle. I think part of the problem is I don't seem to be entering DFCO for some reason so probably some tweaking there needed as well. I recently completed a 7747 to 8625 w/$OD mask swap and am still working out the bugs. Thanks for the input!

  2. #2
    What kinda of steps are your seeing? Is the TPS and throttle blade set correctly?

  3. #3
    Carb and Points!
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    When driving the IAC counts range from 75 to 110 but the majority of the time they are around 80. Most of the time the IAC counts are under 15 at idle and closer to zero when in gear. TPS is set at .55 volts or so and I think the throttle blade settings are correct.
    Here is a shot from idle
    Idle Screen Shot.jpg

    And one while driving
    Driving screen shot.jpg

    These are the current IAC settings. I haven't changed them from the factory BHMX bin settings yet.
    IAC settings.jpg
    Last edited by Cooker; 05-28-2015 at 08:28 AM. Reason: Changed photo

  4. #4
    Fuel Injected!
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    This is easy to do in Holley's new EFI systems and software.
    You adjust your throttle blades till the system balances at 2% at idle, the ecm learning will adjust the base fuel table to the Air Fuel ration table.
    So I guess you could adjust your throttle blades till you get close to the correct A/F at idle then reset your tps? Fine tune your A/F from there?
    Richard
    1969 C-10 SWB Step
    355 Small Block
    Stock Vortec heads
    Howard's Cam (110951-08)
    Stealth Ram, Holley HP EFI
    700R4 Trans, 2200 stall & 3.73 gears

  5. #5
    Carb and Points!
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    The Holley system w/software sounds like a nice alternative but I am running a factory bin with Tunerpro to modify and emulate for it. The Holley TBI unit is the 502-6 OE replacement unit for my 1990 Chevy K1500. Thanks for taking the time to reply though!

    Did anyone who did a Big Block TB to SBC swap on their truck have to change these settings? My reasoning is that with the larger throttle body CFM vs factory throttle body CFM flow would that then necessitate a proportional change to the IAC settings to compensate?

  6. #6
    Fuel Injected!
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    Changing the throttle body size shouldn't affect the idle as the idle airflow is directed through the idle air control valve. It will, however, affect the fueling at anything above closed thottle.

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  7. #7
    Carb and Points!
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    Quote Originally Posted by buddrow View Post
    Changing the throttle body size shouldn't affect the idle as the idle airflow is directed through the idle air control valve. It will, however, affect the fueling at anything above closed thottle.

    Buddrow
    That makes sense, then I won't change these settings for now and continue tuning. Thank You!

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