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12.5 gpm weldon mechanical fuel pump

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Hello,

can someone tell me until what power does this fuel pump support! I have fixed it into a car which runs on pure methanol, running 18 injectors on the aiming for lambda 0.61 car dropped fuel pressure on about 3 bar of boost.

fuel pump is drive by the crank belt has -10 hose on both end which sucks fuel directly out of a tank in the engine bay.

fuel pressure increases smoothly just up to 7000rpm after that it keeps on dropping from 8 bar up to 4-5 bar

Good question and a quick check on the Weldon web page for that pump is an example of why one must be careful of what is being advertised.

All it has is 3000hp fuel injected at 80 PSI - there is NO mention of the pump rpm or, for that matter, the flow curve over the rpm range. Neither does it specify the fuel as that 3k on a race gasoline/petrol type fuel may be only a little over 1k on methanol because of the volume requirements.

My personal preference would be to return it as unfit for use - but as this may not be possible you're going to have to try contacting them directly for actual flow and rpm values or fabricate your own test rig with corrected rpm - I assume it is camshaft driven rather than belt?

Something to check, though, in the meantime, is that the feed side to the pump isn't restrictive - that's a LOT of fuel volume being drawn through the lines and you should check the pressure drop at the pump* - it may need larger lines - also, many fluid fittings are quire restrictive in their bores, some are much better than others and they're usually referred to as 'large bore' or similar - I know XRP have a line of them - https://www.xrp.com/

*One thing that many overlook, and that can be the cause of a hesitation or flatspot on launch, is that the vehicle's acceleration adds to the effective vacuum head as the fuel also has to be drawn up against the acceleration forces and will this increase the chance of vapourisation from the pressure drop and so stop any liquid fuel being drawn into the pump, even if it doesn't, it will reduce the fuel flow. This will normally show as a dip in fuel pressure as the pump cannot maintain it. It may be worth considering some form or accumulator to counter this, if it is a problem.