[Diy_efi] CIS EFI via Fuel Pump PWM

Brian Michalk michalk at awpi.com
Wed Aug 7 14:22:35 GMT 2002


Am I missing something here?
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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