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Fuel supply for throttle bodies


kennedyj

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I'm going to convert my Weber-fed engine to throttle bodies and I'm not sure of the best/easiest way feed the HP fuel pump.  Currently I have a Facet Red Top situated adjacent to the standard Westfield fuel tank.

I'm toying with the idea of retaining the Facet and feeding the fuel to a reservoir/air-separator under the bonnet and then feeding the HP pump from this.  This would mean I only have to worry about a return pipe to the existing fuel tank.  Doing this would mean I could keep the existing tank and low-pressure pipery.

Has anyone tried this, know of a suitable reservoir or if the idea is viable?

-JohnK.

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DVAndrews

A proper way to do this is to use a close coupled surge pot which ensures an uninterrupted supply of fuel to the engine, if an injected engine's fuel pump has an interruption of supply , even momentarily, the engine will stumble. Since the fuel pump delivers fuel all the time with the excess bled back to the tank, even the smallest amount of fuel movement away from the fuel pickup will cause the engine to cut-out and die.There is no reservoir of fuel such as that in a carburettor.

Normally measures are taken insde the tank to ensure that when cornering the fuel does not move away from the pick-up under centripedal force, the usual measures involve baffling or a closed compartment with one way valves. An alternative is to mount a small surge tank of about a litre and a half to two litres capacity near the tank, this is then fed by your Facet or similar with an overflow back to the tank, the surge tank should be tall and thin to minimise the effects of surge, this surge tank then feeds the high pressure fuel pump by gravity, the return from the fuel rail is then taken to the surge pot rather than the tank so that it is recirculated. This will minimise the problems associated with fuel surge.

There is no reason why you shouldnt mount the surge pot remotely except that you would have a 2 litre reservoir of highly explosive fuel in the engine bay.

Dave

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I had considered the low pressure pump / surge pot route, but discounted it on the basis that :

a) you need to buy a surge pot;

b) you end up with two fuel pumps = twice as much to go wrong !;

c) the plumbing can get messy; and

d) it can be quite heavy.

In the end I opted for a fuel injection tank from Westfield - it has a surge bowl on the bottom so the pump shouldn't run dry and it means I only have one fuel pump to worry about.  OK, so you end up with two fuel lines running to and from the engine bay, but it seemed a much neater and more reliable solution in the long run.

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BTW, there seems to be a market for second hand fuel tanks and red top pumps so you could sell those to help pay for the new fuel tank.

Just a thought...

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Burtons do one - but it's only listed in their catalogue (no picture).

Also AH Fabrications (one of the pages in the 2002 Demon Thieves Catalogue) make them.

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DVAndrews

I can do you a quick drawing if you want one, sometimes access to the tank / internals and replacement tanks arent available.. making a surge pot isnt so hard although I aprreciate that having two fuel pumps is not ideal.

Dave

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