Min. injector off time

[Ward Williamson]

  Good, but let me add some stuff here.  
In an automotive App. don't be concerned about 90+% duty cycle at peak
rpm.  How long do you spend there?  And if it's long enough to Hurt to
Inj. driver or the Inj. I don't want to be with you.   When your
dealing with marine or aircraft app's start worrying about it, because
they tend to run at WOT for long periods of time.  The problems with
to large of injectors is you loose fuel control at idle.  Say time to
full open on a peak and hold is about 1.2 ms and your 35 lbs/hr
injectors work bitchen at 8000 rpm or so but at idle you only need 1.0
ms on time you'll loose all the consistency your trying to gain with
fuel injection.
You'd be better off going with a higher fuel pressure and a smaller
injector.  
  Another trick is to run peak and hold driver's with a saturated
switch injector,  It'll open real quick and want hurt anything.
  Gotta go!
Ward  




---bruce plecan <nacelp at bright.net> wrote:
>
> Please someone help me on this.
> "They" say not to run the injectors over 85% PWM,
> on time.  OK, from what I've read the lag time from
> V on till injector open can range from .0012 sec 
> Peak+Hold to .0018 sec for Saturated.  Right?
> But when they say 85% if the injector was on for
> 85 days, and off for 15, then that would be a 85%
> on time, but the injector might be crispy by then.
> So what is a min. off time that would allow an
> injector to "relax"+"cool-off" enough??..
>   If there is this .0018 reaction time, would then 
> a .002 sec. be considered a min. off time?????..
> If not what would be????.
>   Would be above be a new consideration for
> a high rpm motor for injector sizing????...
>   TIA  Bruce    
> 
 
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