[Diy_efi] Donegan ECU

[Steven P. Donegan]

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.
>