Author Topic: Experience with fuel pump flow rates and Webers  (Read 1611 times)

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Offline StephenH

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Experience with fuel pump flow rates and Webers
« on: Sunday,October 14, 2018, 11:22:30 PM »
I'm a little premature with my question while I'm still looking into my vehicle symptoms, but this is the internet.......

Had my first full noise outing with my rebuilt crossflow S2 and in general all very positive.

The rebuild is a '160HP Alpine spec' build in most respects.
The fuel delivery is straightforward, Facet pump (I'll work out the rating once I get the number off it), filter and 2x 45mm Webers.
Previously this has been adequate and  the car was competitive in sprints and hillclimbs with several course records, now it's noticeably stronger up top.....
But it's also now running out off fuel on wide open throttle after about 8-10secs or so of full noise in the 100-120+kph range and high load.

So I'm going through the basics of checking the filter, confirming the pump rating and measuring the actual fuel pressure (which I'm assuming needs to be 3.5-4lbs on Webers).
In the meantime, what sort of fuel flow rating have others used with success (or lack of success as that also helps me)?
Stephen
54/1690 1969 S2

Offline 4129R

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Re: Experience with fuel pump flow rates and Webers
« Reply #1 on: Sunday,October 14, 2018, 11:31:37 PM »
How old are the petrol tanks?

I have known all sorts of crap get into the tanks and partially block the outlet tubes.

It might be worth draining both tanks, and blasting compressed air back up the tubes, or pushing thick electrical wire up them to clear any blockage. 

Offline EuropaTC

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Re: Experience with fuel pump flow rates and Webers
« Reply #2 on: Monday,October 15, 2018, 01:45:02 AM »
I run the Facet electric pump on the Elan (TC/Webers) with a pressure restrictor set to 2psi.  The pump is supposed to be 3.5-4psi as standard but I've seen several references where it's stated that webers need high volumes at low pressures (Des Hammill for example) and 1.5 to 2.5psi seems to be the range to go for.

I don't have a problem with mine, but then again there's nowhere around here where I could drive it at full throttle for any time without either losing my licence or ending up in a ditch !

Brian

Offline StephenH

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Re: Experience with fuel pump flow rates and Webers
« Reply #3 on: Monday,October 15, 2018, 02:14:09 AM »
The pump is a Facet e11*72 /245*95/54*0536*00
I think this is rated at about 32gal/hr, which sounds like plenty to run a 1600 with a nominal 160hp.
So back to the basics, either something is blocked or the pump is actually failing (I have no idea how old it is).

Yep, I'll have a good poke around the tank, lines and filter for gunk.
« Last Edit: Monday,October 15, 2018, 02:41:08 AM by StephenH »
Stephen
54/1690 1969 S2

Offline Pfreen

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Re: Experience with fuel pump flow rates and Webers
« Reply #4 on: Monday,October 15, 2018, 03:47:33 AM »
Fuel pump flow depends a lot on installation.  Suction lift, fuel filter and also suction leaks admitting air.

Offline jbcollier

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Re: Experience with fuel pump flow rates and Webers
« Reply #5 on: Monday,October 15, 2018, 04:52:38 AM »
Disconnect the carbs and put the hose into a calibrated container.  Run for one minute and then you will know for sure.  I suspect you need a larger capacity pump myself.

Offline jbcollier

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Re: Experience with fuel pump flow rates and Webers
« Reply #6 on: Monday,October 15, 2018, 05:29:36 AM »
How to find the model number:

https://www.pegasusautoracing.com/document.asp?DocID=TECH00023

Some Facet pumps have built-in filters.

Max flow is usually at minimum pressure so you might need twin pumps in parallel.

Offline Clifton

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Re: Experience with fuel pump flow rates and Webers
« Reply #7 on: Monday,October 15, 2018, 06:23:02 AM »
Disconnect the carbs and put the hose into a calibrated container.  Run for one minute and then you will know for sure.  I suspect you need a larger capacity pump myself.

I second this. It's the only way to know exactly what you are putting out. Factory ratings are under perfect conditions.

Offline surfguitar58

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Re: Experience with fuel pump flow rates and Webers
« Reply #8 on: Monday,October 15, 2018, 02:19:07 PM »
I’ve been having a similar conversation on this thread: http://www.lotuseuropa.org/LotusForum/index.php?topic=2431.0
Let us know what you end up installing.
Tom
"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away."
Antoine de Saint-Exupery

Offline StephenH

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Re: Experience with fuel pump flow rates and Webers
« Reply #9 on: Monday,October 15, 2018, 03:59:19 PM »
I’ve been having a similar conversation on this thread: http://www.lotuseuropa.org/LotusForum/index.php?topic=2431.0
Let us know what you end up installing.
Tom

Will do Tom.
Stephen
54/1690 1969 S2