[Healeys] Why carry spares

[I Erbs]

Great idea...who has the bits and the time????

Ira Erbs
IT Educator and Consultant
Portland, OR.

Sent from my mobile phone. What you get may not be what I typed.
On Mar 19, 2014 5:14 PM, <rwil at sbcglobal.net> wrote:

> Could it possibly be time for some physical measurements on a test
> setup to see: what output pressure with two pumps in series, both 2 SU
> and 1SU and 1Facet (or similar), and in parallel? and what happens
> when one of the pumps in series packs it in?
>
> From reports here it looks as if SU pumps are pretty patient with all
> possible setups.
>
> -Roland
> On Wed, 19 Mar 2014 16:01:59 +0000 (UTC), you wrote:
>
> >OK, I'm not a theoretical physicist, and don't play one on TV, and we're
> not
> talking electronics so I don't see how running two pumps in series doubles
> the
> output pressure. AFAIK, the output pressure of an SU pump is determined by
> the
> strength of the spring that pushes the diaphragm (presuming the solenoid is
> strong enough to compress an even stronger spring). There may be some
> internal
> 'regulation'--there is a small hole between the input and output chambers
> on
> BN1/2 pumps that may provide a pressure limit by bypass--but no real
> pressure
> regulation. So, if the spring is capable of producing, say, 3PSI when the
> solenoid is switched off, then the output to the second pump will, at most,
> push the spring back some but it wouldn't add to the 3PSI.
> >
> >IOW, a spring capable of pushing a diaphragm at 3PSI won't be able to
> push at
> 6PSI, just because the incoming pressure is greater. Anyone actually
> measured
> the pressure of two SUs in series?
> >
> >Bob
> >
> >----- Original Message -----
> >
> >
> >
> >Two pumps in series might not be suitable for a racing Healey, but they
> have
> >worked just fine on my street BJ8 without any problems for a long time.
> >It's just simpler to plumb them in series than in parallel, in my opinion.
> >If you have two pumps in parallel with separate switches, then you can run
> >both pumps at the same time and get twice the flow rate at the same output
> >pressure. Running two pumps in series at the same time will provide the
> >same flow at double the output pressure - not good for the carbs. So, for
> >pumps in series there should be only one switch to prevent running both
> >pumps at the same time.
> >
> >
> >
> >Steve Byers
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