Fuel pressure manifold reference -DIY_EFI Digest V5 #62

[Clare Snyder]

>
> > -----Original Message-----
> > From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> > Behalf Of Andy Wyatt
> > Sent: 11 February 2000 06:47
> > To: diy_efi at diy-efi.org
> > Subject: Fuel pressure reg/EGO Qs
> Date: Fri, 11 Feb 2000 11:57:50 -0500 (EST)
> From: Mary or Stephen Burgess <msburgess at conestoga.net>
> Subject: Re: Fuel pressure reg/EGO Qs
>
> At 05:47 PM 2/11/00 +1100, you wrote:
> >Hey y'all
> >
> >Could someone please explain to me:
> >
> >1. Why do they have fuel pressure regulators manifold pressure
referenced?
> >Why don't they just take this into account in the fuel map? Is it so that
> >the injectors are open longer at idle, improving trimmability and hence
idle
> >quality?
> >

In order for an injector to be properly calibrated you need to know the
pressure drop across the nozzle - ie how much difference between rail and
manifold. No simpler method than referencing the regulator to manifold
instead of atmosphere.
This means at high manifold vacuum the rail pressure drops so a given
opening time produces the same flow as it would under load when manifold
vacuum is low and rail pressure increased.


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