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Old 01-31-2009, 02:16 AM   #1
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Default Explain pulse widths

I searched on here and when I couldn't find any related threads I looked it up on wikipedia and google, I find lots of references to pulse widths but I cannot find an actual answer to what the pulse width exactly is.. probably a noob question but I see in datalogs that the PW raises with rpms and seems to be directly related to duty cycle of the injectors.. is it the amount of time the injector is open for in one cycle? Trying to get a handle on this because I've heard people recommend adjusting pule widths for such and such or tuning timing a bit to get the lowest pulse widths..
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-Ryan
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Old 01-31-2009, 02:32 AM   #2
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Originally Posted by ThePass View Post
is it the amount of time the injector is open for in one cycle?
-Ryan
bingo
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Old 01-31-2009, 02:45 AM   #3
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Fuel Injector Pulse Width - What is Injector Pulse Width - Definition of Fuel Injector Pulse Width

do a search noob. Seriously, i searched google "injector pulse width" and that was the first result.
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Old 01-31-2009, 02:45 AM   #4
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Ok so why do I hear some references to trying to achieve low pulsewidths? Wouldn't the leaner you run result in less injector opening time?
-Ryan
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Old 01-31-2009, 03:12 AM   #5
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Quote:
Originally Posted by ThePass View Post
Ok so why do I hear some references to trying to achieve low pulsewidths? Wouldn't the leaner you run result in less injector opening time?
-Ryan
yes... which means you use less fuel...
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Old 01-31-2009, 01:16 PM   #6
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Quote:
Originally Posted by ThePass View Post
Ok so why do I hear some references to trying to achieve low pulsewidths? Wouldn't the leaner you run result in less injector opening time?
-Ryan
because at lower throttle openings and less RPM, you dont need as much fuel.
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Old 01-31-2009, 01:48 PM   #7
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There is also duty cycle, which is related. It is basically the pulse width in ms divided by the time it takes for the motor to complete two full revolutions (on a 4 cycle). You can figure out this time simply by converting rev/min to rev/sec and then invert (bottom divided by the top. At 3k rpm, two cycles is .04 sec (40ms) and at 6k rpm it is half of that (20ms). So if your pulse width is 10ms, you would be 25% dc and 50% dc at 3k and 6k respectively.

sorry for the rant
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Old 01-31-2009, 02:07 PM   #8
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The fuel injector duty cycle (IDC) is the percentage of time the injector is supplied with power. The time during which the injector is powered (or activated) is called the injector pulse width (IPW). During normal engine operation, the fuel injector fires once during the four strokes of the Otto cycle, which last for 2 revolutions of the engine. As an example, at 3000 rpm it takes 0.040 seconds or 40 milliseconds (ms) for the engine to complete 2 revolutions (3000 rpm divided by 60 equals 50 revs per second; invert to get 0.02 sec per rev or 0.04 second for 2 revs). At 6000 rpm it takes 20 ms for two revolutions. If a fuel injector is activated for 15 ms (the IPW) at 3000 rpm the duty cycle is 37.5% (15 ms/40 ms), or rpm times IPW divided by 1200 equals IDC in percent. If an injector is powered for 15 ms at 6000 rpm, then IDC is 75% (15 ms/20 ms). If you know the engine speed (rpm) and the IPW (dataloggers can provide this information), then it is easy to calculate the IDC.


Stealth 316 - Injector Duty Cycle Calculation
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Old 01-31-2009, 03:39 PM   #9
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that is exactly what i just said, just in a different way
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Old 02-02-2009, 03:38 AM   #10
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Impressed at the knowledge dropping guys, very impressed
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