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<... HP pumps are capable of moving LOTS more fuel than a Facet pump ... HP pumps would be drawing fuel through the Facet pump ... because the Facet can't keep up ...>
You're right. I hadn't thought of that. Facet pumps deliver 30 gph. I'll check how much my HP pumps are putting out. Wonder if Facet delivers more at lower head pressure, objective being to push fuel through filter and plumbing so there's less chance of pressure drop that could cause the fuel to vaporize.
Back to the drawing board ... maybe ... Jim S.
Marvin Kaye wrote:
Jim Sower <canarder@frontiernet.net> wrote:
"""
I have a canard, but I will have a Facet pump near (and below) the wing tanks
to PUSH the fuel through the filter and fuel flow transducer. I don't want
the HP pumps to SUCK through the filters and etc. for fear of vaporizing the
fuel.
"""
This doesn't make any sense to me, but perhaps I'm missing something. The HP pumps are capable of moving LOTS more fuel than a Facet pump. Consequently, it seems to me that the HP pumps would actually be drawing fuel through the Facet pump when they're switched on, simply because the Facet can't keep up with what's being drawn out of the sump tank by them. Additionally, a return system needs 2 flow transducers, one for the feed line and one for the return... then the display instrument's electronics deduct the return flow from the feed flow to properly calculate actual through-the-injectors instantaneous flow data. (The EI fuel flow instrument uses an FFDM-1 (fuel flow differential module) to do the job, GRT EIS does it itself, as do other flow instruments with both feed and return inputs.)
As long as the filters are rated to flow as much fuel as the HP pumps are capable of pushing I don't see that (vapoization) as an issue. The filter elements do need to be kept clean, and are a replace-at-annual item.
<Marv>
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