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Old 12-19-2008, 05:51 PM   #1
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Duty Cycle

Hey all, I was wondering if someone could go into depth w/ duty cycle. I've never really understood it!!


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Old 12-19-2008, 07:06 PM   #2
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What exacty do you want to know?
Duty cycle is the amount of time that the fuel injectors are switched on. A duty cycle of 0% means that the injector is not on at all, a duty cycle of 100% means the injector is on constantly. Duty cycle at idle is normally only a few percent, rising as revs or load increases.

Injectors only has a small amount of time to inject fuel into the mixture. So when you are creating more power, you are needing more fuel so the injector will open and stay open longer allowing more fuel into the mixture. Eventually you will get to the point where the injector can not supply enough fuel in the time frame.

This calls for a larger injector which can supply more fuel in a less given time.

So when someone says they are at 70% duty cycle, that means the injector still has 30% left in its cycle.



Also some cars (Not ours) run 100% duty cycle and control the fuel by pressure, but that another story
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Old 12-19-2008, 07:06 PM   #3
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What exacty do you want to know?
Duty cycle is the amount of time that the fuel injectors are switched on. A duty cycle of 0% means that the injector is not on at all, a duty cycle of 100% means the injector is on constantly. Duty cycle at idle is normally only a few percent, rising as revs or load increases.

Injectors only has a small amount of time to inject fuel into the mixture. So when you are creating more power, you are needing more fuel so the injector will open and stay open longer allowing more fuel into the mixture. Eventually you will get to the point where the injector can not supply enough fuel in the time frame.

This calls for a larger injector which can supply more fuel in a less given time.

So when someone says they are at 70% duty cycle, that means the injector still has 30% left in its cycle.



Also some cars (Not ours) run 100% duty cycle and control the fuel by pressure, but that another story
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Old 12-19-2008, 08:00 PM   #4
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Dutycycle is how much work an injector is doing in a given amount of time , or how many times the injector is opened and closed in a given amount of time

50% duty cycle shows that the injector is held open and held closed for an equal amount of time when the engine needs more fuel the time that the injector stays on (its duty cycle) increases so that more fuel can flow into the engine if an injector stays on all the time , it is said to be static (wide open, or 100% duty cycle) and not a good thing

I dont feel it is safe to past 92% MAX

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Old 12-19-2008, 08:04 PM   #5
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so is this the same thing as injector pulse?
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Old 12-22-2008, 12:05 PM   #6
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Injector pulse is usually the actual amount of time that the injector is open, duty cycle is the percentage of is capacity that its operating at.
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Old 12-22-2008, 12:35 PM   #7
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The term "duty cycle" can be used for other devices that cycle on/off . It is not a term only for injector operation.

I think the idle speed motor on the Focus, also has a computer controlled duty cycle......at least some of these controllers operate this way.
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Old 12-22-2008, 03:22 PM   #8
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http://en.wikipedia.org/wiki/Duty_cycle
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Old 12-23-2008, 07:17 AM   #9
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I love this new tuning section. Full of great questions, and very to the point answers.
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Old 12-26-2008, 09:24 AM   #10
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what is the best duty cycle you would reccomend on boosted applications
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