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Author Topic: Injector pulse width read and learn.  (Read 12004 times)

DmC

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Injector pulse width read and learn.
« on: April 14, 2009, 04:23:54 AM »
Pretty sweet article I found in a google search while looking for info on Oscopes.

Pretty much lays out injector tuning theory in simple terms.

http://www.hywell.org/plhelp/injdutycycle.html
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d112crzy

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Re: Injector pulse width read and learn.
« Reply #1 on: April 14, 2009, 01:32:27 PM »
good shit nog.
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stealthiskey

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Re: Injector pulse width read and learn.
« Reply #2 on: April 14, 2009, 07:35:57 PM »
in his math he MULTIPLIES by two, because it takes two full revolutions before the next intake stroke, but I should point out that to find how long each intake stroke lasts you actually DIVIDE by two.

so whereas he says 20ms is 100% duty cycle at 6000 rpm, the intake stroke only lasts 5 ms at 6k rpm.
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BangBusMaster

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Re: Injector pulse width read and learn.
« Reply #3 on: April 14, 2009, 11:26:29 PM »
15ms @ 8000 is what I always remember.  IMHO the ms displayed on the 2d view in CROME is correct and is what I use when judging how much injector is left.
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BangBusMaster

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Re: Injector pulse width read and learn.
« Reply #4 on: April 14, 2009, 11:30:37 PM »
My spreadsheet for duty cycle:



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d112crzy

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Re: Injector pulse width read and learn.
« Reply #5 on: April 15, 2009, 01:41:01 AM »
I'm kinda lost on this, or maybe I'm just thinking too hard. But is this a set ms for all injectors? As in that is just the amount of time there is available for the signal to the injector, regardless of injector or engine because it's directly related to engine rpm/4 engine cycles?

I've always wondered what the Y axis in the 2d fuel graph meant in Crome. Once again, good shit.
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Joseph Davis

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Re: Injector pulse width read and learn.
« Reply #6 on: April 15, 2009, 02:24:15 AM »
15 ms at 8000 rpm is 120% duty.  :(
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stealthiskey

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Re: Injector pulse width read and learn.
« Reply #7 on: April 15, 2009, 08:19:10 AM »
haha.  duty  ;D
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DmC

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Re: Injector pulse width read and learn.
« Reply #8 on: April 15, 2009, 01:09:20 PM »
Quote from: stealthiskey on April 14, 2009, 07:35:57 PM
in his math he MULTIPLIES by two, because it takes two full revolutions before the next intake stroke, but I should point out that to find how long each intake stroke lasts you actually DIVIDE by two.

so whereas he says 20ms is 100% duty cycle at 6000 rpm, the intake stroke only lasts 5 ms at 6k rpm.
I agree with you on that.  ;D I wonder how he thought it was time to multiply. Did the engine suddenly sprout 4 more cylinders? the guy is into dsm's so maybe he's used to parts mulitplying by two when they snap in half?
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DmC

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Re: Injector pulse width read and learn.
« Reply #9 on: April 16, 2009, 12:19:36 AM »
Quote from: d112crzy on April 15, 2009, 01:41:01 AM
I'm kinda lost on this, or maybe I'm just thinking too hard. But is this a set ms for all injectors? As in that is just the amount of time there is available for the signal to the injector, regardless of injector or engine because it's directly related to engine rpm/4 engine cycles?

I've always wondered what the Y axis in the 2d fuel graph meant in Crome. Once again, good shit.
It's the width of the pulse/duration time of the signal sent from the ecu to keep the injector open.

Smaller injectors flow less in a given time larger injectors flow more in the same amount of time.
I'm stating the obvious I know but hey just completing my thoughts.
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snm95ls

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Re: Injector pulse width read and learn.
« Reply #10 on: April 18, 2009, 10:59:42 AM »
Quote from: stealthiskey on April 14, 2009, 07:35:57 PM
in his math he MULTIPLIES by two, because it takes two full revolutions before the next intake stroke, but I should point out that to find how long each intake stroke lasts you actually DIVIDE by two.

so whereas he says 20ms is 100% duty cycle at 6000 rpm, the intake stroke only lasts 5 ms at 6k rpm.

I don't think you are interpreting the math correctly.

Quote from: Joseph Davis on April 15, 2009, 02:24:15 AM
15 ms at 8000 rpm is 120% duty.  :(

Huh?

I get 15 ms at 8000 RPM to complete a full Otto cycle.

 ???

I am sure there is something I am missing.
« Last Edit: April 18, 2009, 11:08:59 AM by snm95ls »
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BangBusMaster

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Re: Injector pulse width read and learn.
« Reply #11 on: April 18, 2009, 08:34:03 PM »
Maybe he's taking latency into it.  But 15ms is the correct window for 8000rpm.
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snm95ls

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Re: Injector pulse width read and learn.
« Reply #12 on: April 18, 2009, 10:19:22 PM »
Quote from: BangBusMaster on April 18, 2009, 08:34:03 PM
Maybe he's taking latency into it.  But 15ms is the correct window for 8000rpm.


That would make sense if you had info to generalize latency.

I didn't think I totally failed at math.

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Joseph Davis

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Re: Injector pulse width read and learn.
« Reply #13 on: April 18, 2009, 11:48:52 PM »
I was drunk last week, so I dunno where I got my figures from.

That being said, 15 ms at 7000 is the rule of thumb for 100% duty.  Inductive reactance + dis/charge time is a bitch.
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patsmx5

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Re: Injector pulse width read and learn.
« Reply #14 on: April 19, 2009, 04:10:47 PM »
Quote from: DmC on April 15, 2009, 01:09:20 PM
Quote from: stealthiskey on April 14, 2009, 07:35:57 PM
in his math he MULTIPLIES by two, because it takes two full revolutions before the next intake stroke, but I should point out that to find how long each intake stroke lasts you actually DIVIDE by two.

so whereas he says 20ms is 100% duty cycle at 6000 rpm, the intake stroke only lasts 5 ms at 6k rpm.
I agree with you on that.  ;D I wonder how he thought it was time to multiply. Did the engine suddenly sprout 4 more cylinders? the guy is into dsm's so maybe he's used to parts mulitplying by two when they snap in half?
Funny shit!  ;D
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