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Thread: Car doesn't want to idle, unless 9 cells are flattened.

  1. #1

    Default Car doesn't want to idle, unless 9 cells are flattened.

    Hello. I've been working on getting this Terminator Stealth tuned for a long time and have just been having very limited success with getting idle sorted out. I recently found out that the car will idle beautifully, _IF_ I have 9 cells within the idle area (in other words, the target idle cell plus one cell around it in every direction) set to nearly the same fuel flow rate (~6.18-6.23 lb/hr). My normal warm unloaded idle cell is the 800-900 RPM, 45-48 kPa range. Car is set to 870 RPM idle, which is 47 kPa.

    A problem I'm having in addition to this is that the loaded idle (A/C on) wants a lot more fuel than the unloaded idle, which makes it nearly impossible to smooth out the fuel table. When the A/C is on, it sits in the 51-54 kPa range. At this time it seems to want around 7.3 lb/hr of fuel, and obviously it's very difficult to smooth out a cell from the 6.18 lb/hr to the 7.3 lb/hr range!

    If I have the fuel table smoothed out instead of "flattened" in the idle area, idle swings around cyclically. Nothing I have done seems to make it happy. The throttle plates are set correctly, with IAC sitting at about 4-5% when idling at 870 RPM/14.0 AFR. I've attached a zip file with my GCF and my most recent test of warm (unloaded) idle and A/C (loaded) idle: 07132019_Step3_FinalFile.zip

    Relevant specs on my car are as follows:
    1966 Mustang, 289 ci V8 bored out 0.040" over, 9.5:1 compression, probably <300 HP.
    0.486"/0.496" lift, 214°/238° duration, 112° LSA flat tappet cam.
    Weiand Stealth 8020 intake.
    Tri-Y headers, 2.25" exhaust, WBO2 sensor located 8" from where all of the "Y"s collect, and 10" from the end of the header.
    Pertronix I ignition, new plugs/wires/rotor/cap, dual mechanical advance distributor, NO IGNITION CONTROL.
    Fuel pressure set at 44 PSI.

    My concern is that though the car will run like this, I'll have problems when I go to areas of different elevation (I'm heading into the Colorado Rockies in a couple of weeks). When I've got a lower kPa at idle due to elevation, the whole table will be messed up. I'm going to try a vacuum reference line for the fuel pressure regulator, but otherwise I'm unsure what to do. Advice?

  2. #2
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,391

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    Look at your Base Fuel Table in VE Graph form and you'll see your problem. Why have the Closed Loop come on at 150°F? You do know that the Learn won't turn on until the Coolant Temp Enrichment gets to 100%, and in your case that's at an engine temp of 200°F. If you were using timing control you could use Idle Spark control to help smooth the idle.
    Last edited by 81 TransAm; 07-13-2019 at 08:50 PM.

  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,716

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    Quote Originally Posted by Kelly_H View Post
    A problem I'm having in addition to this is that the loaded idle (A/C on) wants a lot more fuel than the unloaded idle, which makes it nearly impossible to smooth out the fuel table. When the A/C is on, it sits in the 51-54 kPa range. At this time it seems to want around 7.3 lb/hr of fuel, and obviously it's very difficult to smooth out a cell from the 6.18 lb/hr to the 7.3 lb/hr range!
    Read 4th & 5th paragraphs: http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information) and http://forums.holley.com/showthread....e-Tuning-Notes (EFI Idle Tuning Notes)

    If I have the fuel table smoothed out instead of "flattened" in the idle area, idle swings around cyclically. Nothing I have done seems to make it happy.
    Try the "5.0L Ford" Advanced Idle Control under IAC Control.
    I further improved it with the CUSTOM Idle Control Parameters listed HERE under "IAC Motor".
    http://forums.holley.com/showthread....neral-IAC-Info (General IAC Information - Read "IAC NOTES")
    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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