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Thread: Possible False Lean At Idle

  1. #1

    Default Possible False Lean At Idle

    I have a BBF 521 with a Holley Dominator. We got it running earlier this spring and it's running really well. My tune targets 14.0/1 at idle but it smells a little gassy to me and I wonder if I could be experiencing the false lean condition from large cam overlap that the manual talks about. My cam isn't quite as large as the example given in the manual, but it has a decent amount of overlap. Should I try moving my Closed Loop threshold above 1500 RPM and lean the Base Fuel Table a bit around idle? Some specs below and my Global File is attached:

    521 BBF
    Kaase P-51 heads
    Dominator non-sequential MPFI
    Injectors: Holley 522-668 66 lb/hr

    CAM:
    =============================================
    Straub S98060
    Classifications:
    P/N STR BBFCHR
    Cam Type Hyd Roller
    Serial Nb S98060
    Grind Nb FF 299/318-09HR

    Lift:
    Intake Exhaust
    Lobe Lift 0.3677" 0.3420"
    1.73 Ratio 0.636" 0.592"

    Geometry:
    Centerline Angle 103° 115°
    LSA 109°
    Overlap 33.5°
    Duration @ .050" 243° 260°
    Duration @ .015"
    Duration @ .006" 299° 218°

    Timing @ .050":
    Open 18.5° BTDC 65° BBDC
    Close 44.5° ABDC 15° ATDC
    ================================================== ====
    Attached Files Attached Files
    Last edited by dalcini; 06-05-2019 at 01:02 PM.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,085

    Default

    Yes, you can tune the idle in Open Loop mode.
    http://forums.holley.com/showthread....e-Tuning-Notes (EFI Idle Tuning Notes)
    http://forums.holley.com/showthread....ension-Harness (Read "Wideband O2 Sensor 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.

  3. #3

    Default

    Thanks Danny. I've read this post from you on several occasions. I haven't messed with fuel in a while and could use some guidance while leaning my idle. I figure it probably smells gassy when too rich, but don't really know what traits indicate too lean? Engine stumble? Running hot? As always, your help is greatly appreciated!

  4. #4
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,454

    Default

    You can probably clean up your idle a little by getting a cam sensor and use sequential instead of Untimed Sequential. You could then set the Injector End Angle at idle, so the fuel is injected after the exhaust valve closes.

  5. #5
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,085

    Default

    http://forums.holley.com/showthread....0396#post70396 (Injector End Angle Tuning Information)
    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.

  6. #6

    Default

    Thanks guys. Now I know what Injector End Angle does! Cam sensor is on the list for this winter. Right now I’m enjoying the car after a three year hiatus.

  7. #7

    Default

    Does it smell rich or does it smell like raw fuel? You say "gassy" which makes me think it's raw fuel? If so, it's not necessarily rich, but raw fuel is injected during overlap and shoots right out the exhaust. So I'd second Danny in that you need to go to true sequential.

    I have a smaller cam in my 454 BBC (231°/239° hydraulic roller). With true sequential and a 14.2 Target AFR the exhaust doesn't smell much of anything. Just an old car smell as it doesn't have cats.

  8. #8

    Default

    Thanks Zwede. The "gassy" smell was a bit of raw fuel, so I agree as well. Cam sensor will be a good winter project. In the meanwhile, I'll use this summer to enjoy the car and better familiarize myself with some of the advance tuning areas of the V5 EFI software.

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