On Wednesday 16 April 2003 13:53, Alex Harford wrote:
> On Wed, 2003-04-16 at 11:36, Picdude wrote:
> > > Since the pressure in the fuel rail is pretty much
> > > constant (and easy to measure if needed), all I need is a relation
> > > between injector pulse width and amount injected.
> >
> > Not exactly constant, so you should measure.  When tuning/setting up =
the
> > car, it's common for the mfgr to require the vacuum line (to the fuel
> > pressure regulator) be disconnected as the vacuum level is used to ch=
ange
> > the fuel pressure a bit.
>
> Fuel pressure at the rail changes, but the pressure differential betwee=
n
> the fuel line and the intake manifold remains constant.  This is becaus=
e
> of vacuum in the intake.

Good point.  I was thinking about supercharged/turbocharged cars, like mi=
ne. =20
The supercharger has an "FMU" (fuel mgmt unit) that raises the pressure t=
o=20
almost 100psi (from 40) with only ~14lbs boost.  This somewhat simulates=20
having higher-rated injectors.

Cheers,
-Neil.

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