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doing some research.... vacuum ported fuel pressure regulator??



On Fri, 7 Mar 2003 06:36:40 -0800 (PST)
Neal Tovsen <nealtovsen@yahoo.com> wrote:

> > Would a CIS car be considered a vacuum ported fuel
> > pressure regulator?
> 
> Ummm...I don't know jack about NOx, but that doesn't
> sound right to me.
> 
> Maybe my terms are mixed up, but "vaccuum ported FPR"
> sounds more like and EFI FPR with a vaccuum/boost
> reference. Like Digifant I, and many other "modern"
> EFI systems. They run a vaccuum line to the FPR, which
> allows the FPR to set pressure referenced to the
> intake manifold, instead of referenced to atmosphere.
> It's mostly a forced-induction car thing.

It could also be something to do with that the pressure transducer has
it's own inbuilt vacuum reference (like a barometer) so it measures the
absolute intake pressure, not relative the atmospheric.

> I seem to remember something about a bit from a CIS
> Audi Turbo car that allows CIS to maintain constant
> fuel pressure relative to boost.

Yes

> But I have no idea what that has to do with NOx. But I
> don't know much about that anyway...

This is how it works with single rail electronic fuel injection, I don't
know about CIS

Normally the regulator is there just to maintain the fuel pressure at a
fixed pressure relative to the intake manifold pressure (whether the
engine is normally aspirated or not) so there is a known presdsure
differential fuel flow through the injectors.

A tap off NOx feed line bleeds into & pressurises the fuel regulator
when the NOx is switched on, giving you higher fuel pressure and hence
enrichment for the NOx.

--Andrew