[Bulk] RE: [Diy_efi] Donegan ECU

[Steven P. Donegan]

KISS is always my principle :-) Given that most of the inputs and
outputs are a grand total of like 1 square inch or less of real estate
(and that is only cause I'm doing this with old school stuff, not
surface mount) having things on-board and unused is OK.

On Thu, 2007-01-04 at 22:12 -0500, Daniel Nicoson wrote:
> I would vote to "keep it simple Sam".  The "normal" return type fuel system
> with a mechanical/pneumatic regulator works great, why add complexity?
> Remember, you won't b e tuning the car.  It will be some other bonehead that
> doesn't fully understand your system.  When he mucks it up, your system gets
> blamed.  Keep it only as complicated as it needs to be.
> 
> Ford uses the return-less fuel systems and modulates fuel pressure on the
> newer Mustangs; and I'll bet most of their other cars.  I think it is to get
> emissions that much cleaner, not having warm fuel vaporize...
> 
> I have "heard" that some of the 2003 Cobras have problems on shifts with the
> pressure spiking and then being too low after the shift.  I don't know how
> prevalent this problem really is.  I know there are tuning parameters in the
> program code that can be adjusted.
> 
> I would suggest that fuel pressure control by PWM of the pump motor would be
> too slow except to make up for longer duration events (longer than 2
> seconds).  Compared to changing injector PW, motor control is much slower.
> 
> My vote, keep it simple.
> 
> Good luck with the project.
> 
> Dan Nicoson
> 
> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
> Behalf Of Steven P. Donegan
> Sent: Thursday, January 04, 2007 7:49 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] Donegan ECU
> 
> I can't quite read this as a yes or a no to fuel pump pressure control -
> can you give me a binary response :-)
> 
> I.E. does fuel pressure sensing/fuel pump control make sense for an EFI
> system or not.
> 
> Thanks!
> 
> On Fri, 2007-01-05 at 08:00 +0900, Bernd Felsche wrote:
> > On Friday 05 January 2007 00:57, Steven P. Donegan wrote:
> > > I had not thought of fuel temp at all - every vehicle I drive
> > > would consume the gas in the rails well before it got warm :-)
> > > However this does raise a point - perhaps my ECM/PCM/EFI computer
> > > needs a way to open a fuel return line and to sense fuel temp in
> > > the rails? Any ideas on how useful that would be in the 'real
> > > world' anyone?
> >
> > Superflous if you're running in closed-loop; which you would be if
> > the fuel rail was warm enough to make a difference.
> >
> > If the temperature in the fuel rail is a problem, then a
> > recirculating fuel pressure control system is IMNHSO a better
> > solution. In such a system, there's always "fresh" fuel that's in
> > excess to the amount required for injection from the tank flushing
> > the rail(s). The fuel tank is the cooling environment for the fuel.
> >
> > Pressure regulation also happens at the rail(s), whereas in
> > "dead-end" systems it's at the fuel pump, perhaps a several metres
> > from the rail and therefore the injectors. That increases the
> > difficulty in controlling the pressure (time delays that depend on
> > fuel pressure and temperature); especially if it's to vary
> > dynamically wrt manifold pressure.
> >
> > The ability to vary the fuel rail pressure is at least desirable to
> > get consistent injected quantities due to a fairly constant pressure
> > difference across the injector; between the fuel rail and the
> > manifold where it's injecting.  Makes for simpler calculations on
> > injected quantity.
> >
> > If you're stuck with a "dead-end" fuel delivery system, then you
> > need to add a return line and a valve that vents the rail(s) back to
> > the tank in the interval between the fuel pump running and the
> > engine actually being started. The time delay will depend largely on
> > the free-delivery rate of the fuel pump and the volume of the fuel
> > rail(s). That ensures that there's "cold" fuel in the rail(s) before
> > you start injecting it.
> >
> 
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