Re: Ford injectors (& Question) MORE

["Dave Zug" <dzug@delanet.com>]

I beleive Carl's reference to DC was based on the 6000 rpm thingy like I had
originally been using as a baseline reference for this thread....  At least
thats the way I read his appreciated info.

Clarification never hurts though.. we tend to drift into assumptions about
what others base knowlege is.  notice how many times the word '730' is
thrown around. this thing used to be called "ECM: GM Part Number 1227730"
when we were part of the DIY_EFI mailing list   ;-).

A wise lister once gave me the advice... "you are on a public forum" and
that I should try to type using better sentance structure. Guess the lesson
is that the audience is very wide and we lose touch in the excitement
sometimes.



----- Original Message -----
From: Roger Heflin <rah@horizon.hit.net>
To: <gmecm@diy-efi.org>
Sent: Friday, August 25, 2000 3:55 PM
Subject: Re: Ford injectors (& Question) MORE


>
>
> On Fri, 25 Aug 2000, Bruce Plecan wrote:
>
> >
> >
> > >     Sounds like you have the right idea....When the injector(saturated
> > > circuit) gets above 85% commanded duty cycle you can start seeing the
> > > unstable AFR's...
> >
> > At what rpm?
> > Things I've played with seem fine up to like 6K
> >
> > In real world the injector seems to become unstable around
> > > 81-82% real duty cycle.....so I guess what I am trying to say is even
if
> > you
> > > get to the 85-90% commanded duty cycle...
> >
> > A workable strat., that seems to be forming is just hammering em open
and
> > staying there on some hot turbo stuff.
> >
> > I still woudn't worry about the
> > > life of the injector as long as AFR is stable...
> >
> > Now you make the second guy to say this, what is going on here.
> > Are you saying starting a 81-82 DC the AFR can start to be unstable?.
> > Bruce
>
>
> I think the problem here is that everyone is trying to use duty cycle,
> and duty cycle means nothing to determine lockup problems.    Off time
> is the controlling factor.   A 85% duty cycle is just fine at 2000 rpm
> (off time of 4.5ms), and the same 85% duty cycle won't work at 7000
> rpm (0.72ms off time), so using duty cycle as a rule of thumb does not
> work.    Knowing how small of off time is unsafe is alot better rule
> to use, and this varies based on what injector you have, but somewhere
> around 1.0-1.5ms should always be safe (this is what one of the
> aftermarket is supposed to claim)  go less than 1ms of off time
> at any rpm and you are going to be in trouble regardless of what the
> real duty cycle is.
>
> Roger
>
> ----- End of forwarded message from owner-gmecm@diy-efi.org -----
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