[Healeys] Why carry spares

[Oudesluys]

Chris,

That would be a flow test, not a pressure test, which is certainly not 
the same.

For a pressure test you would need a fuel pressure gauge to measure the 
output pressure of :
1: one single pump, nr. 1
2: one single pump, nr. 2
3: two pumps in line, nr. 1 pump switched on  and nr. 2 pump switched 
of, the result should be similar to test 1
4: two pumps in line, nr. 2 pump switched on  and nr. 1 pump switched 
of, the result should be similar to test 2
5; two pumps in line, both pumps switched on, the result should be the 
sum of test 1 and 2

In all test situations the flow should be more or less the same, 
depending on the resistance in the output line. You would only double 
the flow if you have the pumps fitted in parallel.

It is assumed that Lucas type pumps are used. Other type of pumps may 
give different results in test 3 and 4 and the flow test. E.g. gear and 
vane type of pumps may show no or little flow and pressure in these 
tests as they will (partially) block the fuel line when not switched on.

Kees Oudesluijs
NL

Chris Dimmock schreef op 20-3-2014 3:10:
> It's pretty simple to test.
> Just disconnect the fuel line, point it into a bucket, turn the one pump on,
> run it for 30 seconds, and measure the volume of fuel in the bucket.
> Empty the bucket.
> Then turn both pumps on, run them for 30 seconds, and measure the fuel pumped
> into the bucket.
> Report back here.......
> That volume of fuel x2 is the delivery volume per minute.....
> X 120 = volume per hour.
> It's not Formula one, close enough is good enough, you won't get in trouble
> with the FIA....
> Easy.
> Best
> Chris.
>
> Sent from my iPhone
>
>> On 20 Mar 2014, at 11:14 am, 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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-- 
Kees Oudesluijs
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2995XG Heerjansdam
T: 078-677 1233
E: coudesluijs at chello.nl

Technische commissie Jensen Healey en GT
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