My injector duty cycle is at 130%?!? Calculation help needed
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TECH Apprentice
Joined: Dec 2001
Posts: 351
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From: CA
My injector duty cycle is at 130%?!? Calculation help needed I just autotapped my car and did a couple of WOT blasts. Everything looks good, timing is average 28 degrees and my O2 is alittle high, averaging 0.925. But when I calculated my duty cycle, it came out to peak at 130% at 6600 rpms. Am I miscalculating it? Well, I assume I must be, since there's no way a duty cycle could be more than 100%. My injector pulse width at 6600rpm was 24ms. What would be my duty cycle? I still have 99 injectors in my car. Does it sound like I need some real injectors?
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
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From: Troy, AL
Re: My injector duty cycle is at 130%?!? Calculation help needed Max duty cycle at 6400 would be 18.75ms theoretically.
What are your mods? You could have a fuel pressure problem. You might also see what leaning those O2s back to around .870mv would do.
What are your mods? You could have a fuel pressure problem. You might also see what leaning those O2s back to around .870mv would do.
Thread Starter
TECH Apprentice
Joined: Dec 2001
Posts: 351
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From: CA
Re: My injector duty cycle is at 130%?!? Calculation help needed Oops, forgot to add details about my setup. I have H/C with stock fuel injectors. It's also a C5. So yeah, it seems totally bizarre that my PW could be 24ms at 6600 rpms. How can autotap be that inaccurate, isn't it just reading the OBD2 computer? Thanks.
Staging Lane
Joined: Dec 2001
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From: Nationwide
Re: My injector duty cycle is at 130%?!? Calculation help needed The computer can output 200% duty cycle, of course the injectors will just be on all the time. You are seeing the commanded duty cycle by the PCM which ofen goes over 100% you need tuning or bigger injectors. Duty cycle goes up as RPM's increase since there is less time between pulses.
20ms @ 6000 RPM is 100% 24ms is 100% @ 5000 RPM
Mike
[ February 26, 2002: Message edited by: Ramchargers ]</p>
20ms @ 6000 RPM is 100% 24ms is 100% @ 5000 RPM
Mike
[ February 26, 2002: Message edited by: Ramchargers ]</p>
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Thread Starter
TECH Apprentice
Joined: Dec 2001
Posts: 351
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From: CA
Re: My injector duty cycle is at 130%?!? Calculation help needed [quote]Originally posted by Ramchargers:
<strong>The computer can output 200% duty cycle, of course the injectors will just be on all the time. You are seeing the commanded duty cycle by the PCM which ofen goes over 100% you need tuning or bigger injectors. Duty cycle goes up as RPM's increase since there is less time between pulses.
20ms @ 6000 RPM is 100% 24ms is 100% @ 5000 RPM
Mike
[ February 26, 2002: Message edited by: Ramchargers ]</strong><hr></blockquote>
So if it is over 100%, it must be injecting fuel on the compression stroke or something right? How can that be possible, unless I have some really high fuel pressure. So what injectors should I go with? Any recommendations?
<strong>The computer can output 200% duty cycle, of course the injectors will just be on all the time. You are seeing the commanded duty cycle by the PCM which ofen goes over 100% you need tuning or bigger injectors. Duty cycle goes up as RPM's increase since there is less time between pulses.
20ms @ 6000 RPM is 100% 24ms is 100% @ 5000 RPM
Mike
[ February 26, 2002: Message edited by: Ramchargers ]</strong><hr></blockquote>
So if it is over 100%, it must be injecting fuel on the compression stroke or something right? How can that be possible, unless I have some really high fuel pressure. So what injectors should I go with? Any recommendations?
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