Fuel Starvation

[Guest danny_samb]

Do I need to run a pressure regulator, put the filter before the 1st pump? Could I wire the pumps to a switch?

[Guest zerorace]

no regulator on the feed to the swirl pot just filters filter in front and behind the pump is always good and one after the injection pump and yes to the switch

[Guest danny_samb]

How much would a tank cost, how easy to fit, don't you need to remove the rear arches and the whole back end to get the tank out

[Guest chris brown]

How much would a tank cost, how easy to fit, don't you need to remove the rear arches and the whole back end to get the tank out

expensive and yes depending on the size of the tank and how it is installed the cheapest way is to use a swirl pot as described

[Longboarder]

I've never understood the overspecing of the low pressure pump. All it has to do is replace the fuel burnt in the engine. The rest of the unused fuel returns to the swirl pot. So cheapest would do but for reliability it is worth buying a decent brand. If you do go for the basic facet cube make sure you use a simple inline filter to feed it. Don't use the facet bullet filter. They clog. Remember the high pressure pump needs very clean fuel in from the pot.

High pressure pump is a different matter (I use an Audi pump off ebay) and should be specced for output, not because your engine will be using 180 litres an hour but because it must have the capacity to maintain the correct pressure in the rail at all times. Injectors need even cleaner fuel than the high pressure pump so put an injection micro filter between HP pump and fuel rail. Final set up should look something like pic below.

 

Nigel

[Guest zerorace]

one reason to spec the low pressure pump high is on a low tank and small swirl pot install the pump has to play catch up after long corners

[Longboarder]

My swirl pot is a foot tall and contains 2 litres when full. Remember fuel unused by the engine is returned to the pot not the tank so the level in the pot goes down at the rate the engine burns it, not the rate the HP pump pumps it. The low pressure/lift pump only has to replace fuel burnt by the engine if the plumbing is correct as per my diagram. All it needs is to reliably supply clean fuel to the swirl pot. Almost any flow rate will do. Certainly 20litres a minute from a facet cube does the job fine.

If for some reason you decide to fit a small three outlet pot and return the unused fuel from the rail to the tank rather than the pot, then Yes, you would need to think very carefully about the lift pump capacity and would still get problems with an unbaffled tank but why would you install a system which just moves the problem around rather than solving it?

 

Nigel

[Guest danny_samb]

What fuel pressure regulator would I need, does your diagram go swirl put, filter, pump then fuel rail, then the pressure regulator back I to swirl pot

[Snapperpaul]

If you currently run injection then that pump is your high pressure pump and the fuel pressure valve is on the end of the fuel injection rail, no need to add any more pressure devices

[brumster]

Don't use the facet bullet filter. They clog.

 

He speaks the truth; I can verify this first-hand

[speedtripledan]

He speaks the truth; I can verify this first-hand

i took heed of these warnings and binned mine before it was to late

[Guest zerorace]

[My swirl pot is a foot tall and contains 2 litres ]

some can only hold 1/2liter due to space and on long corners like Gerards bend at mallory park on full chat would run low time the fuel and car has settled

[Guest danny_samb]

Ye currently running injection, so all I need is the swirl pot, facet cube pump and a couple of filters,

[Longboarder]

Think of the plumbing as a low pressure loop and a high pressure loop.

The low pressure loop goes from tank to £1 clear plastic ebay inline filter to basic facet cube to middle of the pot. Then restricted (3mm) bleed out the top of the pot and back to the tank. This pump runs constantly to fill and bleed air from the pot. As the pot is tall and the return from the rail is above the LP feed there is a tendency for warm fuel returning from the engine bay to be bled back to the tank with any air. The restriction in the tank return quietens the LP lifter/feeder pump a bit.

The HP circuit is bottom of the pot to G.S.F Audi 80 H.P. pump to Pug 106 inline injection microfilter to fuelrail to cheapo ebay injection pressure regulator/pressure gauge and back to close to the top of the pot.

Currently makes 198 bhp.

I haven't had the pleasure of driving Gerrards but am not aware of any fuel failure other than due to facet filter blockage.

 

Nigel

[Bob Tucker]

I always prefer empirical testing, but sometimes theoretical testing can throw some light on a problem too...

 

Say Gerrards is 1/4 mile, to empty a swirl pot of 1/2 litre. the engine will be doing....2 & 1/4 mpg.....

Even pushed really hard on circuit, my car (210bhp) does 12 mpg., so I reckon you'll be well within

the capability of feeding your engine.

 

There are also tables showing that to feed en engine of XXX bhp will require YYY litres of fuel.

I'll look it out & publish it. Ray's engine builder used it to spec the fuel pump for his new twin turbo setup.

http://www.watermanr...fuelpump21.html

the model he needs is 10 gallons per minute...luckily he will only be running for 7.5 seconds!

 

How can you plan your racing fuel system?

Use a hand held calculator and plan on .5 lbs/hp-hr (gasoline)

EXAMPLE: You have a 650 hp engine. 650hp x .5 = 325 lbs/hr (gasoline). Although you need to know how much your fuel weighs, assume for this example that it weighs 6.2 lbs/gal. 325 lbs/hr 6.2 = 52.42 gal/hr. Dividing by 60 (minutes per hour) yields .847 gal/ min (GPM).