Injector Duty Monitor

[Walter Sherwin]

>
>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.