TECHNICAL
APRIL 2016 http://www.yachtingmonthly.com 83HP injection systems
One of the responses to ever
tougher NOx and PM emissions
limits has been the introduction
of high-pressure fuel injection
systems, notably HPCR, in ever
lower horsepower engines. The
latest generation of small (40hp
or more) Yanmar four-cylinder
engines are now HPCR. Whereas
the pressure in conventional
injection systems rarely exceeds
5,000 psi (350 bar), it is not
uncommon to see 30,000 psiHP injection systems‘Sailors are vulnerable
because fuel sits in
our tanks for months
or years at a time’
At one time, diesel fuels
contained up to 40,000 parts per
million (ppm) of sulphur. Starting
in the 1990s, allowable nitrogen
oxides (NOx) and particulate
matter (PM) emissions for road
vehicles were progressively
lowered. The new emissions levels
could only be met with exhaust
after-treatment systems that
would be damaged by even small
amounts of sulphur, so sulphur
limits were steadily lowered to
10ppm – what is known as ultra
low sulphur diesel (ULSD).
Unfortunately, the process
of removing sulphur from
diesel fuel reduces its lubricity
(lubrication properties, which are
essential to injection pump and
injector life), reduces the fuel’s
shelf life, removes inhibitors to
biological growth, and increases
the likelihood of paraffi n wax
formation in colder weather (the
wax then plugs fuel lines andfi lters). Various additives are
put into ULSD to restore the lost
properties. Collectively, these are
known as surfactants.
In recent years Europe has been
introducing biodiesel into the
fuel supply, currently requiring
7% (although implementation
is variable among member
states and is, in general,
lagging). Typically, biodiesel is
blended with petro-diesel at
concentrations between 5% (B5)
and 20% (B20). Most engine
manufacturers will now guarantee
conventional injection systems
with B20 biodiesel but may
limit high-pressure systems
(see below) to B5.Downside of biodiesel
Biodiesel has signifi cant benefi ts
compared to petro-diesel, notably
lowered exhaust pollutants and
better lubricity. But then there’s
the downside, including reduced
effi ciency and power, more cold-
weather clogging, and greatly
reduced shelf life – most engine
manufacturers recommend not
storing B20 beyond 90 days from
the date of production and 100%
biodiesel beyond 45 days. It also
has increased solvent properties,which will attack some rubbers
in older engines and will break
loose ‘gunk’ from older fuel
systems that have been operating
on petro-diesel, resulting in
multiple clogged fi lters. It has a
higher retained water content,
which promotes corrosion of fuel
injection equipment and microbial
growth, and there’s a greater
risk of injector nozzle coking and
plugging, and high surfactancy
(more on this also below), none of
which is good news for us.PHOTO RIGHT: GRAHAM SNOOK/YM. ABOVE: TIME INC The latest
generation of
Yanmar’s 4-cylinder
engines all use
high-pressure
common rail
injection systemsOlder engines still need
clean fuel, but not to the
level of HPCR systemsPHOTO RIGHT: YANMAR