Injector Control

[Tom Cloud]

>Hi!
>I was study for some time the injector signal , and , in my opinion ,  
>the pulse width can't be constant . The PW increase or decrease ( aprox. 
>between 1% to 85% ) according with throttle position and / or MAP sensor 
>( or airflow sensor ).
>If you have right and the PW it's constant , how you increase the RPM 
>when you press the throttle ? 
>I'm using this type of modulation ( PW ) on my project and 'till now 
>it's
>OK .
>Alex

Alex

if you have a 1 mS pulse width -- held constant.

 - with a period of 100 mS, you would have a duty cycle of 1%
 - 10 mS period would give 10% duty cycle
 - 1 mS period would give 100% duty cycle

So, you can keep the width constant and vary the period to
change the duty cycle (this works on throttle body injection
systems -- wouldn't be feasible for port injection)

If you have port injection, you'd need PW (pulse width)
modulation, since the injectors are timed with the rpm of
the engine (in the scenario above, the timing is totally
unrelated to the engine rpm, but here, it's tied directly
to it).

But, with either scheme, isn't it the injector open time
in relation to the injector firing rate (PW/PRR) that
determines the amount of fuel delivered ???  And this is
duty cycle, is it not?  And duty cycle is easily measured
(it's called a "dwell meter" and we all have one of those --
or at least I do  8^)

Tom Cloud

        Ever stop to think .... and forget to start again ??