[Diy_efi] CIS EFI via Fuel Pump PWM

huw scourfield huw.scourfield at btinternet.com
Sun Aug 11 02:43:56 GMT 2002


Well let us all know, eh?
    Huw
----- Original Message -----
From: "Mike" <erazmus at iinet.net.au>
To: <diy_efi at diy-efi.org>
Sent: Friday, August 09, 2002 12:43 AM
Subject: Re: [Diy_efi] CIS EFI via Fuel Pump PWM


> At 10:19 PM 7/8/2002 +0100, you wrote:
> >I'm forgetting nothing, instant in this case is relative to having pump
near
> >rail, I just can't see the extra length doing anything.
>
> Well if someone knows the spring constant for the pipes/hoses etc
> Then I'd be interested to see the delta volume from say 30 to 60psi ?
>
> Re: Your first comment, it *will* take time to build pressure from
> idle to WOT - heaps of factors, the rotational intertia of the fuel
> pump rotor is one reason and re my 1st para above - the other factor
> is the delta volume of the fuel rail (in total) - a quick check in
> my lab suggests this is definitely *not* instant ! And is therefore
> a factor to include in any PID algorithm and an indication of
> what sort of current you want to dump into a pump from a boost mode
> SMPS, but of course, empirical evidence aside - I just haven't
> done a delta volume calc taking into account srping constant of
> steel - but I *have* done a quick test, looks like anything from
> 0.1 to 0.2 secs but not sure - I got other more important things
> to do ;-)
>
>
> rgds
>
> mike
>
>
> >    Huw
> >----- Original Message -----
> >From: "Mike" <erazmus at iinet.net.au>
> >To: <diy_efi at diy-efi.org>
> >Sent: Wednesday, August 07, 2002 12:48 PM
> >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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> >> >
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