Originally Posted by
BMWST?
but wont a header tank remove the fuel supply pressure variations ? A header tank will always have say 200 mm of "head"...wont vary (much)
No, the extra volume in a tank adds nothing to the pressure compared to the existing tube. What's causing the problem is the flow restriction downstream from that, and at the very low pressure involved it doesn't take much to restrict the flow. I once organised a clear pvc tube return line up through the steering head and into the fuel cap, just like a normal vent tube. It meant I could see immediately if the pressure dropped at all, you could see the petrol level drop back down the tube.
There are systems that contradict almost every sensible design improvement you can think of, but they mostly involve weird fluids at much higher pressures. I recall one project where doubling the pressure produced almost twice the flow, doubling it again stopped it literally stone cold dead. General rule of thumb, though is doubling the line diameter gives 4 times the flow, at the same pressure.
Which reminds me of a Smokey Unick story. His response to the new, rigorously enforced fuel tank capacity limits was to increase the size of the fuel line to the engine, to about 2".
Go soothingly on the grease mud, as there lurks the skid demon
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