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Thread: Ford 5.0 turbo TBI problem.

  1. #1
    maik21 Guest

    Default Ford 5.0 turbo TBI problem.

    I'm having problems with this.

    AFR reads at WOT 11.5 from 3000 rpm to 4500 rpm but suddenly AFR fall to 18.0.

    TBI injectors are 85 lb/hr and O2 Compensation Limits are +25% from 3000-6500 rpm.

    I'm having max numbers of 165 on the fuel map at 5000 rpm but the numbers for 5500, 6000, 6500 sometimes are in red color even if I put lower numbers in those cells.

    The TBI fuel pressure is at 24 psi. Do I need to raise fuel pressure or put a vacuum fuel pressure regulator in the return line?

    I didn't do a datalog but I'm scared of trying to do it again because of a extreme lean condition.

    Turbo is set for 4 psi and it's very accurate.

  2. #2
    maik21 Guest

    Default

    This is the car. I opened some base maps that came with Holley Commander 950 software and some of them has numbers higher than 200 (value) in the fuel map without being in red.



  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,934

    Default

    Tape a fuel pressure gauge to your windshield and verify you're not losing fuel pressure during wide open throttle.

    Also check the boost referenced fuel pressure regulator is functioning properly. The Holley TBI unit has a 1:1 rising rate fuel pressure regulator. To test it, you can place a rubber tipped blowgun (air pressure regulated down to boost PSI) against the small hole in the driver's side rear throttle bore. (It can also be pressure tested with a Mityvac vacuum/pressure pump.) Then bypass the fuel pump relay, so it runs constant, and view fuel pressure on the gauge. Engine off, of course.
    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.

  4. #4
    maik21 Guest

    Default

    First, I replaced the 5/16 steel feed line with a 3/8 hose i.d.
    I have 2 datalogs. 1 with 20 psi of fuel and another with 15 psi of fuel.

    I have 3 videos of in-car fuel pressure gauge:
    one with 25 psi of fuel,
    one with 25 psi of fuel,
    and the last with 15 psi of fuel.

    When car goes lean, fuel pressure is right.
    Waste gate output is to atmosphere.
    Last edited by maik21; 01-05-2012 at 07:13 PM.

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