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Thread: 4500 Sniper throttle blade adjustment?

  1. #1

    Default 4500 Sniper throttle blade adjustment?

    What's the preliminary adjustment for the throttle blade screws for front & rear barrels prior to doing the idle set? To get equal opening, or does it matter as much as it does with a carb?

  2. #2
    Join Date
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    Connecticut
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    If all four TBI injectors spray fuel at idle, I believe in equal throttle blade opening on the primary & secondary shafts. If only the front two TBI injectors spray fuel at idle, I believe the primary throttle blades should be opened more (secondaries nearly closed). Obviously, a 1:1 or progressive secondary throttle shaft linkage determines how many TBI fuel injectors are spraying at idle.
    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

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    Four are spraying.

  4. #4

    Default

    The reason I asked this is because I have idle RPM set to 1100 when coasting the idle drops to around 800 or even 750. I have tried changing the IAC Decay Time and Hold Time with no change. The RPM ABOVE IDLE TO START RAMP is set at 500. The RPM ABOVE TO RETURN control is set at 100. Is that possibly causing the problem?

  5. #5

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    That is possibly your problem. With "Above Idle To Start Ramp" at 500, the ramp down clock does not even start until you get down to 1,600 RPM. The ECU will ramp down the IAC to 0 for however long you have the decay set. If while coasting that puts you at 700 RPM or whatever, so be it. The IAC will not attempt to recover the engine to the idle speed until the ramp decay finishes.

    I wanted my Sniper setup to act similar to my old carb in terms of decelerating from cruise. So I wanted the ramp down to start very soon after I let off the throttle. To get that "feel" you increase the "Above Idle To Start Ramp". I have mine set at 1,000 which is basically the stock Wizard setting. For you that would mean the IAC would start to ramp down at 2,100. I also wanted it to ramp down fairly quickly so I set the decay time to 2 seconds instead of the standard 4. I just didn't like the feeling of the car "keeping on going" when I let off the throttle due to the IAC being open and holding the RPM up.

    It's hard to describe the feeling in the car so that may not make any sense. LOL.
    Do you have a monster cam? That is just a really high idle RPM. Automatic or stick?

  6. #6

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    What you said makes perfect sense. I have a big cam, but it doesn't need to idle that high. It will idle 500 RPM, I just like the oil pressure at 1100 better and just as important at that RPM, my charging system doesn't drop below 12.5 volts even with everything running. Much below 1000 RPM and the alternator output drops dramatically.

  7. Default

    Have a read through pages 23 & 24: https://documents.holley.com/techlibrary_199r11259.pdf. It discusses the idle operation & tuning basics.
    1970 XW Fairmont (presented as a GT Falcon Replica), 351 Cleveland with Aussie 302 2V closed chamber heads. Edelbrock F351 2V dual plane intake manifold. Camtech CT21544 (234/238@050", 570/579lift, 2600-6200rpm quoted range, 110lobes) 1.73:1 roller rockers. AOD Transmission. Ford 9" 3.5 Diff ratio. Pacemaker #PH4050 2v Tri-Y extractors to 2.5" Hi Flow V-Tex merge pipe with dual 2.5" exhaust through Hooker Aero Chamber Mufflers. Holley Sniper EFI 4150 Super Sniper 650 with HyperSpark Ignition.

  8. #8
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    Quote Originally Posted by Mad Cadder View Post
    What you said makes perfect sense. I have a big cam, but it doesn't need to idle that high. It will idle 500 RPM, I just like the oil pressure at 1100 better and just as important at that RPM, my charging system doesn't drop below 12.5 volts even with everything running. Much below 1000 RPM and the alternator output drops dramatically.
    Get a newer alternator, and try heavier (thicker) oil. Bearing tolerances too loose?

  9. #9
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    Connecticut
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    Hint: Mobil 1 15W-50 synthetic oil, sold at Walmart.
    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.

  10. #10

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    I run 20-50 Royal Purple. It has 30 psi @1000 RPM, 90 psi @ 6000 RPM. I don't like seeing it below 25 even though I realize it’s all in my head and even 15 psi at idle is enough.
    It's not a good idea to idle a large cam slow, it won't get proper oil splash! Alternator is already 140 amp. Car has lots of things pulling amps.
    So I've gone through all that pages 23 & 24 to no avail. It still drops to 800 RPM while the idle RPM is set at 1100 at all points.

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