Injector Duty Monitor

Clarence L.Snyder clare.snyder.on.ca at ibm.net
Thu Jan 7 04:56:01 GMT 1999


Walter Sherwin wrote:
> 
> Ummm....................here's more fuel for the duty cycle fire.  DUTY
> CYCLE, by definition, is the ratio of the ON time of an injector versus the
> ULTIMATE time that it could be turned on per period.  This will vary
> according to the fueling "mode" that the software engineer or OEM has chosen
> (ie:  batch SSDF, batch SSSF, alternating TBI, single TBI, sequential,
> phased sequential).
> 
> If you are worried about dynamic injector performance (as you should be)
> then you have to consider the magnitude of the ON time versus the ULTIMATE
> time available for injection.  This is why an oscilloscope is so invaluable
> in determining injector "headroom", and why many duty meters are somewhat
> meaningless, UNLESS you know the exact firing schedule of your system.
> Beware,  a software package may flip modes based on preset operating
> criteria!
> 
> Take Care;
> Walt.
> >

DUTY CYCLE is calculated, by meters, as the percentage of time the
circuit is "asserted" between event triggers. This means that the
"period" is measured from injector opening to injector opening, or
injector closing to injector closing. The percentage of this period
occupied by the "asserted" mode, or injector energized, is read as DUTY
CYCLE. As such, there is NO requirement to know the firing mode of the
engine, or anything else. It WILL be accurate.
The DUTY RATIO is the ratio of time on vs time off and is generally not
used. This would be stated as 8:2, not 80%. Even with duty ratio, the
effect is the same - conversion is direct as long as the 2 numbers
(before and after colon) add up to 10.

I fail to see how the injection mode can affect this.



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