[Diy_efi] Donegan ECU

[Jason M.]

I've seen them both ways on O.E. applications.  1992 caprice, runs the 
return all the way down and dumps out right on top of the strainer for the 
fuel pump... sits maybe 1/8th of an inch away from the intank fuel pump.

The other, technically it'd would be dropping fuel out halfway up the tank 
is a 1982 caprice diesel (now has a '73 350 oldsmobile, for the last 230000 
or so miles)  Really the return doesn't have much flow (mechanical pump).

I would guess best thing would be to return right on top of the fuel pickup, 
possibly helps flush debris in the tank away from the pickup.

----- Original Message ----- 
From: "Mike V" <efi at dyakron.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, January 04, 2007 7:33 PM
Subject: Re: [Diy_efi] Donegan ECU


> 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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