[Diy_efi] Donegan ECU

[Mike V]

Related to this, is it okay to have the return line squirtin
the fuel in from the top of the tank, or should it be submerged
in the fuel?  I have a 1941 gas tank that I need to plumb a return lin into.
Cheers,
 MV


----- Original Message ----- 
From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
To: <diy_efi at diy-efi.org>
Sent: Thursday, January 04, 2007 6:00 PM
Subject: Re: [Diy_efi] Donegan ECU


> 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.
>
> -- 
> /"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
> \ /  ASCII ribbon campaign | "If we let things terrify us,
> X   against HTML mail     |  life will not be worth living."
> / \  and postings          | Lucius Annaeus Seneca, c. 4BC - 65AD.
>
>
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