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Thread: Injector Duty Cycle

  1. #1

    Default Injector Duty Cycle

    I have Siemens 3105 83lb/hr injectors. How to I determine proper duty cycle & pulse width? Your suggestions would be much appreciated.

  2. #2
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    Quote Originally Posted by Tcnomoney View Post
    How to I determine proper duty cycle & pulse width?
    At idle, cruise, acceleration, WOT? It varies with load & RPM.
    The Data Monitor & Data Logger indicate duty cycle & pulse width (since you're already running the injectors).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, 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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    Quote Originally Posted by Danny Cabral View Post
    At idle, cruise, acceleration, WOT? It varies with load & RPM.
    The Data Monitor & Data Logger indicate duty cycle & pulse width (since you're already running the injectors).
    So these values are preset somehow and not adjustable? Or are they adjustable? If yes, how do I determine the proper values?

  4. #4
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    Quote Originally Posted by Tcnomoney View Post
    So these values are preset somehow and not adjustable?
    Injector duty cycle & pulse width are not adjustable or programmable.
    It also isn't a parameter you tune; it's informational data viewed on the Data Monitor & Data Logger.
    (Although increasing fuel pressure will decrease the injector duty cycle/pulse width and vice-versa.)
    It's the varying end result of how a specific size fuel injector functions on a particularly tuned engine.

    http://www.holley.com/data/TechServi...20Injector.pdf (Proper Fuel Injector Selection Information)
    http://www.holley.com/data/TechServi...ech%20Info.pdf (Fuel Injection Tech Info - Read Last Page)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, 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.

  5. #5

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    Thanks very much Danny. My duty cycle numbers were low which I find just means the injector is sized properly or a little large in my case. What was a little perplexing, was that it seemed from reading the plugs even at an AFR setting of 10, the plugs read that more fuel was needed. I'm running an M4 ProCharger. We bumped the fuel pressure up and then it seemed like too much fuel so I backed down the Target AFR some. Still learning how to tune, but trying not to learn at the cost of an engine. This engine is in a boat which at WOT seems to build heat too quickly. We are thinking it may not have been clearanced properly for marine. Thanks for your help Danny.

  6. #6
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    Just a caveat with the Commander 950 Pro EFI software.
    The following happens with the laptop NOT connected to ECU ('key off'):
    If you open the C950 software and go straight to the datalogger (without loading any Map), the duty cycle will indicate correctly.
    If you first load your Map, then open the datalogger, the duty cycle will indicate exactly half the actual amount, throughout the datalog.
    (I haven't checked what happens when the laptop is connected to ECU & 'key on'.)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, 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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