[Diy_efi] CIS EFI via Fuel Pump PWM

[Mike]

At 08:40 AM 7/8/2002 -0500, you wrote:
>Am I missing something here?

yes, the discussion started with the aim of using fuel pressure
to control flow - ie. *instead* of PWM the injector the discussion
started about PWM the pump. You are right of course if you were
only PWM the injectors - a capacitor is beneficial, but not if
you wanted to modulate the pressure to control mixture...
rgds
mike

>It seems to me that having a long elastic fuel line would be a good thing
>for this application.  It's a capacitor of sorts, trying to keep the fuel
>pressure constant.  I think it would help damp oscillations caused by the
>fuel pump.
>
>Of course given the proper frequency, I suppose it could oscillate too.
>
>> -----Original Message-----
>> From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org]On
>> Behalf Of Mike
>> Sent: Wednesday, August 07, 2002 12:48 PM
>> To: diy_efi at diy-efi.org
>> Subject: Re: [Diy_efi] CIS EFI via Fuel Pump PWM
>>
>>
>> At 11:39 PM 5/8/2002 +0100, you wrote:
>> >Erm, how will it take time to build up? Unless a "long" length of rubber
>> >hose is used, it will be instant.
>>
>> No - instant is not very likely, what does that mean micro seconds ?
>>
>> You are forgetting the rotational
>> inertia of the pump rotor... and the propensity for the fuel pressure
>> regulator to oscillate during a step change in flow/pressure, most outlets
>> of high pressure fuel pumps have a damper - mostly for the injectors
>> but also of value in reducing fuel pressure diaphragm flutter...
>>
>> rgds
>>
>> mike
>>
>>
>>
>>
>>  There might be an issue with dynamic flow,
>> >but given adequately sized solid tubing I would suggest this would be
>> >minimal.
>> >    Huw
>> >----- Original Message -----
>> >From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
>> >To: <diy_efi at diy-efi.org>
>> >Sent: Monday, August 05, 2002 1:44 AM
>> >Subject: Re: [Diy_efi] CIS EFI via Fuel Pump PWM
>> >
>> >
>> >> ARKK tapped away at the keyboard with:
>> >>
>> >> > I asked this a week or two ago. I'm still hoping someone will ut in
>> >> > their two cents about the viability.
>> >>
>> >> > The idea was that CIS injectors could adequately be controlled via
>> >> > fuel pump modulation for pressure control.
>> >>
>> >> Unlikely to be successful unless the pump is quite close to the
>> >> injector. System delays will be the source of control problems;
>> >> it'll take a while for the pressure to build up over a couple of
>> >> metres of fuel line.
>> >>
>> >> What will you do to _reduce_ the pressure when load reduces?
>> >>
>> >> --
>> >> /"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
>> >> \ /  ASCII ribbon campaign | I'm a .signature virus!
>> >>  X   against HTML mail     | Copy me into your ~/.signature
>> >> / \  and postings          | to help me spread!
>> >>
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