At 12:03 PM 7/24/2013, Alistair Bell wrote:
>Well, it is a USG (US Gauge) pressure gauge. You can't be doubting
>those readings can you?

You'd be amazed at my ability to doubt gauges.  I've got a lovely
little chromed-brass vacuum gauge made by USG for Gomco, the (at one
time anyway) pre-eminent maker of medical suction devices.  It's
pretty, readable, responsive, and irritatingly far off.

>Yup, Bentley gives value in Bar and psi. 2.5 Bar = 36.25 psi.
>Leaving aside gauge error, I was just wondering if the extra 2psi
>would be enough to enrichen things beyond the O2 sensor's control ability.

Hollow laughter, since the ECU has the demonstrated ability to follow
a shorted sender down into super-rich will-barely-idle hell.  But
remember that the system should operate (except for emissions)
perfectly with sensor and CAT removed.  My California-spec '84 was
delivered that way in Germany and didn't get its CAT and lambda
sensor until it arrived in the US in 1991.

So lessee...stoichiometric mixture is 14.7:1.  Best economy mixture
is about 16.7:1, best power mixture is about 13.3:1.  If the system
is aiming for stoich at 2.5 bar, 38 psi will bring it rich by 4%, to
about 14:1.  I don't think you have a worry.  And of course the
feedback system will get its sticky fingers in there, mis-read the
misfiring cylinder as lean and screw your mixture up completely.

Yours,
David

>cheers
>
>ab
>
>
>On 2013-07-24, at 8:39 AM, David Beierl wrote:
>
> > At 10:47 AM 7/24/2013, Alistair Bell wrote:
> >> I got a value of  (at idle, vacuum hose on/off) 32/38 psi.
> >>
> >> Bentley says it should be "approx. 29/36psi.
> >>
> >> I'm wondering if my readings are within acceptable range or are
> indeed too high?
> >
> > I wonder how accurate your pressure gauge is.  The spec I believe
> is 2.5 bar, and your regulator certainly appears to be
> regulating.  The only way to see how it's doing in transient
> response would be to use/make a differential gauge that uses
> manifold pressure instead of ambient as a reference.  If you did
> that it should show a basically static reading of 2.5 bar under all
> engine conditions.
> >
> > It's a spring-loaded diaphragm blowoff valve that vents to the
> tank return line.  I've never had one apart, but seems to me the
> spring could perhaps get weaker but not likely to get stronger, and
> I don't *think* there's a lot of opportunity for it to get
> sticky.  The usual failure is a leaky diaphragm that pours gas into
> the manifold through the vacuum line.
> >
> > Yrs,
> > d
> >