DIY_EFI Digest V4 #440

[Gary Derian]

Yes, the box is a good way to pressurize everything on the carb and yes the
fuel pump must reference pressure so fuel pressure remains a constant above
boost but the carb will still go lean as boost comes up because it cannot
compensate for the increased air density under boost.

Gary Derian <gderian at oh.verio.com>

> Subject: Re: Supercharged carb set ups
>
> >         Just a mention.  Studebaker used blow through carbs on it's
> > supercharged V8s in the 50s and 60s.  The trick they used was to
> > builda pressure box around the whole carb, avoiding the problem of
> > reduced fuel flow by pressurizing the bowl to boost pressure.  The
metering
> > can then be kept consistant.
> >         They used a regular Carter AFB 4-bbl, no modifications other
than the
> > pressure box.
>
> Almost. If you look at the top of an ordinary mechanical fuel pump, you
> will see a small hole in the cover. This is the pressure reference for
> the pump. Studebaker added a line from here to the blower output so that
> fuel pressure rose with boost. In case of a ruptured diaphragm in the
> pump, this would cause the crankcase to be pumped full of gasoline.
>
> - --
> Robert W. Hughes (Bob)
> BackYard Engineering
> Houston, Texas
> rwhughe at ev1.net