Does Lycoming make any sense?

The pressure drop across the nozzle orifice is the absolute pressure into
the nozzle less the absolute pressure in the manifold. I don't have a
system diagram here, but I believe the factory fuel flow gauge is a
differential pressure gauge referenced to manifold pressure.

"Capt.Doug" wrote in message
...
"Stan Prevost" wrote in message
I don't think so, at least not very much decrease. I think the fuel will
divide among the functioning injector nozzles. This is why the pressure
increases when one is blocked, the fuel is forced through a fewer number
of
orifices, causing a greater pressure drop across them.

If we are talking about the OEM 'flowmeter', how many transducers does it
have? It would need two to measure a pressure drop. It needs only one to
measure the pressure near the spider. If it has only one transducer near
the
spider, and a nozzle clogs, the remaining nozzles won't flow enough to
relieve the increased pressure and the result will be an increased 'flow'
indication.


But I believe they flow all the metered fuel (or nearly all of it) as long
as the fuel pump provides sufficient pressure. Do you think the fuel flow
out of the fuel injector body (fuel servo) decreases if one nozzle clogs?
Once there is enough restriction to flow so that the "back pressure" from
the spider approaches the fuel pump pressure, then flow will reduce, but
until then, I think the servo maintains the flow it wants.