DaveFJ
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| posted on 20/11/06 at 11:41 AM |
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Inj vs Carb fuel flow rates?
Been doing a little research....
How come fuel injection pumps seem to flow so much less than carb pumps?
the average FI pump seems to output about 13 galls/hour which seems to be pretty much the lowest output facet pump available for carbs ??
Dave
"In Support of Help the Heroes" - Always
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nick205
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| posted on 20/11/06 at 11:59 AM |
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As I understand it, FI needs high pressure (to create the fuel rail pressure for the injectors to work), but not necessarily high flow, where as carbs
need much less pressure (so the needle valves aren't overcome), but like a higher flow.
does that help?
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DaveFJ
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| posted on 20/11/06 at 12:06 PM |
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Yup - was just curious as I am trying to find a suitable pump to match (slightly exceed) the flow from my tank to my swirl pot to the flow from my FI
pump.
I reckon I need a 18Gall/hour pump to fill the swirl pot.
According to the data I have looked up my standard Sierra 2.0 FI pump puts out 13.5 Gall/hour so that should work out nicely...
Does this seem about right to people with more knowledge than I ?
Cheers
Dave
"In Support of Help the Heroes" - Always
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Schrodinger
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| posted on 20/11/06 at 12:33 PM |
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The Sierra pump is a high pressure pump though and you only need low pressure to feed the swirl pot, I would suggest that you would be better to have
too high a volume so that the pump will stall when the pot is full. I used the lowest rated facet pump in my system with a VW Golf GTi injection pump
and accumulator (swirl pot) on a 1.8 Zetec.
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Dusty
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| posted on 20/11/06 at 02:08 PM |
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If the return from the fuel injectors goes back to the swirl pot then the only fuel 'loss' from the pot is what is used in the engine. Any
low pressure pump should keep up easily. If you have a restrictor with a hole of max 2mm in the return line from pot to tank that should reduce the
work the lifter pump does even further.
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mark chandler
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| posted on 20/11/06 at 09:54 PM |
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EFI works on overfueling the rail so the pumps supply too much fuel at a higher pressure than the regulator to ensure you never get a weak mixture,
its a wasted fuel system with the return going back to the tank.
Most EFI systems run between 2.5 and 3.5 bar, however if you stick a gauge on the pump will push up to around 5 bar with teh return blocked.
Carbs just suck fuel so you only need to supply a little more than Wide Open Throttle WOT can cope with.
Regards Mark
[Edited on 20/11/06 by mark chandler]
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