The amount of fuel injected on mechanically governed engines is
controlled by the governor (inside the IP as a rule) along with a
mechanical over-ride to permit max fuel when the governor doesn't
"think" it's needed. On electronically controlled engines, it's the
computer. Diesel engines will NOT run reliably at low speeds or idle
without a governor, it's almost impossible to manually control the
fuel delivery well enough since it's just a tiny, very short duration
squirt at TDC or a bit before.
To get the correct fuel/air ratio under load, there must be a
metering system that measures the air induction rate, either a flow
meter or a pressure transducer correctly calibrated.
Black smoke indicates overfueling, but it will also result from
incorrect injection timing -- this is very evident in older US made
diesels of all kinds due to the use of fixed injection timing set for
correct timing at around 2000 rpm. Very much deviation from that rpm
and the timing was seriously off -- which means under load as the
gears are changed a huge cloud of black smoke from too early
injection (and the horrlble sound of the engine knocking very badly)
is produced until the rpm gets up to 2000. Mack and Screaming Jimmes
were the worst, but they are all bad about it. Easy to tell the ones
with variable timing -- not only are they quiet, but no smoke.
All new engines have soot traps, and so smoke isn't usually visible.
Peter
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