[Diy_efi] Donegan ECU

[Steven P. Donegan]

While I agree that multiple injectors (2 per cylinder) is absolutely the
correct way to go. However 3 of the vehicles I intend to put this system
on do not have the physical real estate (supercharged ford and harley)
to fit 2 injectors or on the camaro - 2 injectors will be an instant tip
off to the California smog police :-( In any case it is only one driver
FET and some source code to support PWM so I'll make it available.

On Sat, 2007-01-06 at 17:48 -0800, Carter Shore wrote:
> On 2007-01-06 John Gross <jogross3 at hotmail.com> wrote:
> 
> > ... However, you
> > touched on an issue 
> > which could cause potential problems under idle,
> > when you desire precise, 
> > repeatable control of your total injector flow, and
> > that is that you can 
> > lower the pressure too much for that level of
> > control of fuel for a given 
> > injector. ...
>  
> > ... if you are dealing with an injector
> > that is designed to run at 
> > 45 psi, and you then subject it to 90 psi rail
> > pressures, your opening and 
> > closing events will be much different than at the
> > design pressure.  This 
> > will obviously effect the total fuel delivery at a
> > given "design" pulse 
> > width for the injector.
> ....
> > The most difficult part of the whole strategy of
> > lowering your pressure at 
> > light load and idle conditions is finding that
> > minimum allowable fuel 
> > pressure that still gives good, repeatable fuel
> > flows while still 
> > maintaining a good enough spray pattern for a high
> > quality combustion event.
> 
> There is some info out there on injector behavior vs
> pressure. The 'pressure' is the difference between the
> fuel supply and the manifold. That's why mechanical
> fuel regulators are referenced to the manifold, and
> why fuel pumps on boosted motors must be capable
> delivering required volume of fuel at fuel supply
> pressure *plus* max boost.
> 
> Contemporary automotive injectors have to be operable
> under a wide range of conditions, from low voltage
> during cranking, to extremes of temperature, and of
> fuel pressure.
> 
> So tweaking pressure by 10%, or even 20%, is not
> pushing too far. There are lots of folks running in
> that band without any issues.
> 
> I cannot think of any reason why an injector would not
> open at very low pressures, although as you state,
> atomization could suffer.
> 
> But many injectors do have a max pressure, above which
> they *will not* open at all.
> 
> The extra cost of multiple injectors (and control
> electronics) is not the big deal to specialist and
> hobbyist folks like us, it's the performance that we
> want. 
> So I believe that multiple injectors, either staged,
> or of different flow rates, are a more straightforward
> method than fuel pressure control via ECU.
> 
> Carter
> 
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