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RE: Ford injectors (& Question) MORE
I think we're saying the same thing....but I think Roger said it
better....Great to backtrack and double think sometimes...Thanks Roger.
-Carl Summers
-----Original Message-----
From: owner-gmecm@diy-efi.org [mailto:owner-gmecm@diy-efi.org]On Behalf
Of Dave Zug
Sent: Monday, August 21, 2000 11:50 PM
To: gmecm@diy-efi.org
Subject: Re: Ford injectors (& Question) MORE
----- Original Message -----
From: Roger Heflin <rah@horizon.hit.net>
To: <gmecm@diy-efi.org>
Sent: Monday, August 21, 2000 7:21 PM
Subject: Re: Ford injectors (& Question) MORE
>
>
> On Mon, 21 Aug 2000, Dave Zug wrote:
>
> > Sorry to keep this going, but I have more:
> >
> > I analized the pulse widths that I am getting (383 CI TPI w/ stock 22#
> > injectors, 360 HP est) verses the max PW for a range of RPM's (3600 -
5500
> > : My "drag zone") and although I am seeing 13 ms pulses, they occur in
an
> > rpm range that allow a maximum of 16 msec thus my duty cycle times are
FINE!
> >
> > RPM/ MAX Allowable PW/ Measured PW /Measured Duty Cycle
> >
> > 3600 16.7 12.9 77.4
> > 3750 16.0 12.3 76.875
> > 3900 15.4 12.4 80.6
> > 4050 14.8 12 81
> > 4200 14.3 11.6 81.2
> > 4350 13.8 11.2 81.2
> > 4500 13.3 11 82.5
> > 4650 12.9 10.8 83.7
> > 4800 12.5 10.5 84
> > 4950 12.1 10 82.5
> > 5100 11.8 9.3 79.05
> > 5250 11.4 9.2 80.5
> >
> >
> > Conclusion: My stock 22# TPI injectors are correctly sized for my
stroker /
> > large tube / header / 13.1 E.T. setup, even though I have PW's that are
over
> > 10 ms.
> >
> > Right or Wrong???
> >
>
> Dave,
>
> I don't think you understand. 10 is the limit at 6000rpm, since your
> motor never gets to 6000rpm this limit means nothing. The max
> allowable is the magic number, you willl have problems if you get
> within 1ms of the max allowable for the current rpm with your
> current pulsewidth, so if you got to 10.4 at 5250 then you would be
> getting dangerous. 9 ms is the exact same thing but at 6000 rpm where
> the max allowable is 10.0.
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?
>
> 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".
Now I can move on to that 6 speed swap in the 92 MAP car ;-)
Thanks again Roger.
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