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Thread: Idle Tuning - Speed Density vs. Alpha-N

  1. #1
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    Apr 2014
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    GA
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    Default Idle Tuning - Speed Density vs. Alpha-N

    I've been using Alpha-N for almost a year, because I couldn't get a consistent idle using Speed Density. Engine idles between 60 & 65 kPa. I've been satisfied, it idles. I read this on YellowBullet: http://www.yellowbullet.com/forum/sh....php?t=1852514, and it got me thinking. Today I changed to Speed Density, and it would not idle. I didn't adjust the throttle body idle screw. If it idles fine in Alpha-N, would it be normal to have to adjust the idle screw just because I switched to Speed Density?
    '81 Mustang Cobra/LSX powerplant
    Poorly built ERL LS454 rebuilt by Extreme Racing Engines
    1.27 60', 9.14@150.47

  2. #2
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    Nov 2013
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    Chicago IL
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    Default

    It's likely a fueling issue. When you switch from Alpha-N to Speed Density, your cells in the Base Fuel Table where it idles will be VERY different.
    Alpha-N, Idle is always the lower left corner of the table.
    Speed Density, it's going to be somewhere else, guaranteed.
    You'll need to do almost a complete retune of the Base Fuel Table, after switching from Alpha-N to Speed Density.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  3. #3
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    Apr 2014
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    Default

    OK, I bumped the idle via the idle screw, set Learn to 100% above 800 RPM, Closed Loop & Learn Compensation to 100%, and switched to speed density. It was idling at 1200 rpm, and came down as I was adjusting the idle screw until 1000 rpm. Anything below 1000 rpm and it stumbles & dies without the IAC catching it. As it begins to stumble, I can see the IAC fluctuate, but it's too late to control the idle speed. P Term 50, D Term 70.
    '81 Mustang Cobra/LSX powerplant
    Poorly built ERL LS454 rebuilt by Extreme Racing Engines
    1.27 60', 9.14@150.47

  4. #4
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    Apr 2014
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    GA
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    Default

    Will "Learn" adjust the idle fuel, or do I need to do that manually?
    EDIT: I have the idle fuel good but it dies when the fans kick on.
    Last edited by SSSTANG; 06-26-2016 at 02:28 PM.
    '81 Mustang Cobra/LSX powerplant
    Poorly built ERL LS454 rebuilt by Extreme Racing Engines
    1.27 60', 9.14@150.47

  5. #5

    Default

    Do PWM control for the fans.
    Andrew

  6. #6
    Join Date
    Apr 2014
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    GA
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    Default

    Coming in the future. Didn't you use a Z06 controller? In the meantime, how can I keep it idling when the fan kicks on?
    '81 Mustang Cobra/LSX powerplant
    Poorly built ERL LS454 rebuilt by Extreme Racing Engines
    1.27 60', 9.14@150.47

  7. #7
    Join Date
    Dec 2009
    Location
    Connecticut
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    23,059

    Default

    Quote Originally Posted by SSSTANG View Post
    Coming in the future. Didn't you use a Z06 controller?
    http://forums.holley.com/showthread....0372#post60372 (PWM Electric Cooling Fan Instructions)
    http://forums.holley.com/showthread....0371#post60371 (PWM Electric Cooling Fan Instructions)

    In the meantime, how can I keep it idling when the fan kicks on?
    http://forums.holley.com/showthread....5701#post75701 (Similar Forum Post)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, 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.

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