Injector Duty Monitor

[Clarence L.Snyder]

Walter Sherwin wrote:
> 
> >
> >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.
> 
> I agree with everything you have said, but ONLY when the entire period
> between event triggers can be used for the purpose of injection.  What if a
> portion of the period between triggers is programmatically inhibited?
> 
> Consider this example...... A sequentially injected, V8, at 5000 RPM, with
> say a 7ms commanded pulsewidth, and operating under the guidance  of a
> control system which only permits injection to occur during a portion of the
> engine airflow cycle defined by 20 degrees BTDC through to 40 degrees ABDC.
> 
> The period between consecutive "Start" triggers, for a given injector would
> be about 24ms (lets call this "Maximum" time).   The period between the
> "Start" trigger and the target "End" trigger for that same injector would be
> about 8ms (lets call this "Ultimate" time).   The real Duty Cycle of the
> injector would then be 7ms/8ms = 87.5%?       On the otherhand, would your
> meter not interpret this as 7ms/24ms = 29%?
> 
> You can also run into a similar problem with TBI fueling, if the system you
> are using can flip/flop from synchronous (event driven) delivery to
> asynchronous (time driven) delivery.
> 
> If you don't agree then please let me know!  You're in Ontario too?  What
> part?  Say "Hi" sometime, offline.
> 
> Take Care;
> Walt.
>From Waterloo Ontario - yes it would read as you state - but no problem.
What we are trying to do is make sure the injector is not "locked on" or
run in fire-hose mode. The "experts" say 80% is maximum, and in the
scenario you propose, anything approaching 80% would be impossible.