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Re: Ford injectors (& Question) MORE




On Mon, 21 Aug 2000, Dave Zug wrote:

> 
> 
> I have 9.2 at 5250, where the max allowable is 11.4, an 80.5 % duty cycle. I
> think I see what you are saying, that 9.2 is really more like 10 than 9
> with pintle speed or coil field release delay?

9.2 should be about 9.2 (well minus the .3-.6 open time-which is
figured into the9.2 already by the coputer).  When things get bad is
when yu get the injector not closed long enough <1-1.5ms close time,
and then the injector no longer takes .3-.6 to open, it opens much
quicker and much more fuel than expected is injected, so a partially
closd injector may only take .1-.3 to open then you are getting .2 to
.3 more fule than expected with no way to control.

 > 
> >
> > So all of your logic is correct, you just seem to think 10ms is some
> > magic number.   And your car is probably firing the same way mine is,
> > ie twice per cam revolution, once per crank revolution.  The only real
> > magic number is 1ms, and you need to keep it closed at least that long
> > or things get iffy, keeping it closed for 1.5 may be safer but 1ms is
> > supposed to do it at least for some injectors.  The problem with duty
> > cycle is that 90% is perfectly safe at 5000 rpm but the same 90% at
> > 7000 rpm leaves the injec tor closed for too short of a time and
> > problems will occur.
> >
> 
> That gives me a firmer grasp on things and I see what you are saying and I
> think it was close to what I was thinking if not what I was typing.  It's
> not a real problem with my setup since I have SVO 24 pounders to put in as
> soon as this leg of experimentation is over. The car shifts at 5300 ideally
> so I'm really on the virge of saying the injectors are appropriate (they
> ARE, IMO). There aren't too many 383's with stock TPI lower intakes on them
> but I wanted to see if the single investment of a stroker shortblock was
> feasable as an economical approach to a gradual performance build up. Most
> people might think they have to get the good intake and headers all at the
> same time but as long as you can live with a milder motor for a while the
> stock 350 components can be put on "for now".


Put an intake on that motor that will let you rev and the 24# will be
necessary.   My motor would have required right at 9ms on 24 lb
injectors, and probably enough more to be a problem given that its
peak hp was at 5800 and was being shifted at 6000 and usually went to
around 6300-6400.   I just did not want to get 24# and then later need
to upgrade them again when I rebuilt the motor (which I am doing now).


				Roger

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