Re: Ford injectors (& Question) MORE

[Roger Heflin <rah@horizon.hit.net>]

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 -----
----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org