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Thread: Using IAC for cruise control?

  1. #1
    Join Date
    May 2018
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    Question Using IAC for cruise control?

    I have a 1991 Mustang 347 (5.0L base) with the HP EFI system. I have a GM IAC (square four wire) and I'm wondering if I could use it for cruise control. My idea for this is flip a switch inside the car to trigger an input to the ECU, then it would manually open the IAC to 100% of a predefined amount. By doing this, I'd think it would be enough to keep me moving at a decent speed in overdrive.

    If there is anyway to override the IAC Position while still letting it do it's job normally, I'd love to know. Side note: Should I set the IAC Hold Position to 100%? I have it set to 30%, but 100% seems to make more sense since I will have more air, and then more power as well. Any help is appreciated. My first idea is to try an Advanced Table, but I haven't dug into that much, thanks.
    347 SBF N/A hand built, 1991 Fox Body Mustang, rebuilt AOD, HP EFI 3.5" LCD display, 7" Digital Dash & both I/O Adapters. Dublin Ohio, 18 years old, built not bought.

  2. #2
    Join Date
    Dec 2009
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    Connecticut
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    Quote Originally Posted by paddyrk View Post
    If there is anyway to override the IAC Position while still letting it do it's job normally, I'd love to know.
    The Advanced ICF does have IAC Position Offset & Target Idle Speed Offset type tables.

    Side note: Should I set the IAC Hold Position to 100%?
    No, not in the Idle ICF.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, FRPP 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 tires.

  3. #3
    Join Date
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    But the TPS would be at 0% and if it was above your idle RPM it would be in Ramp Down mode and the Closed Loop would be turned off. You would also need to use the idle RPM Offset in the Advanced ICF.

  4. #4
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    Dec 2009
    Location
    Connecticut
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    Yeah, I didn't say it was a good idea!
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, FRPP 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 tires.

  5. #5

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    Quote Originally Posted by Danny Cabral View Post
    Yeah, I didn't say it was a good idea!
    I concur with Danny. This is all bad. Andrew

  6. #6
    Join Date
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    I concur with Danny and Andrew. There is no way using the IAC driven to 100% will function as a cruise control. It would work fine as a fixed speed against a fixed load, such as a generator set. But as a control for engine speed versus variable load such a motor vehicle on varying road surface, vehicle speed will be up & down, and would not be a reliable safe mode of relaxed controlled transportation. Gary
    Regards, Gary

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