Measuring injector duty cycle.
Thread Starter
On The Tree
Joined: Mar 2008
Posts: 150
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From: Acworth, GA
Measuring injector duty cycle. I read all I can to learn as much as possible, but I have yet to learn a thing about injector duty cycle. I understand the concept behind it, but don't know how it is measured.. 
I have read hours and hours worth of tuning docs and forums over the last several months and this is something that I don't know a thing about. Can anyone enlighten me on the topic? Or does anyone have a link where I can read up on this? Maybe I'm not looking in the right spot.
I have read hours and hours worth of tuning docs and forums over the last several months and this is something that I don't know a thing about. Can anyone enlighten me on the topic? Or does anyone have a link where I can read up on this? Maybe I'm not looking in the right spot. 
Thread Starter
On The Tree
Joined: Mar 2008
Posts: 150
Likes: 0
From: Acworth, GA
Ok. So if I use my scanner to read injector pulse width at a given rpm I can calculate what the duty cycle is. This will have to be done under load, like on a dyno right? (or big hill maybe?).. What percentage duty cycle would I set as a limit? I've read anywhere from 75-85%, but also read that is the max you want - what would be an ideal range?
Be easy on me, I admit I am a little ignorant. I just like to know everything I can about it.
Be easy on me, I admit I am a little ignorant. I just like to know everything I can about it.
Actually, you could measure it reasonably closely with a DMM
(though the interesting bits usually happen at speed with the
hood closed).
Duty is "on" time divided by period.
If you hook a meter to the injector and one to the IGN voltage
(or IGN is so stable that you can just read & forget) then your
ratio of measured injector voltage over IGN voltage is your duty
(leaving aside some things like the saturation voltage of the low
side switch, which should be small).
(though the interesting bits usually happen at speed with the
hood closed).
Duty is "on" time divided by period.
If you hook a meter to the injector and one to the IGN voltage
(or IGN is so stable that you can just read & forget) then your
ratio of measured injector voltage over IGN voltage is your duty
(leaving aside some things like the saturation voltage of the low
side switch, which should be small).
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
It's a fairly simple concept, 2xLS1 gave the formula for calculating it...
it is the percentage of time out of 2 complete engine revolutions (1 complete cycle, 4 strokes) that any 1 injector is on for.
it is the percentage of time out of 2 complete engine revolutions (1 complete cycle, 4 strokes) that any 1 injector is on for.
