18-07-2012, 04:19 PM
Next-generation boxer diesel
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sprays are not made to overlap
each other by the swirl. The
engineering team also focused
on the lowered compression
ratio, which is aimed at
decreasing the combustion
temperature to reduce NOx.
The combustion temperature
has been decreased by about
100°C. As well as satisfying the
Euro 5 NOx limit, the influence
of the low compression ratio on
theoretical thermal efficiency
and on PM emissions has
been minimized.
The development team
concluded that the best
compression ratio for the Euro 5
system is 16.0, compared with
16.3 in the Euro 4 system.
The final feature to be
introduced is the lift sensors for
the variable nozzle-type
turbocharger actuator. The lift
sensors help to keep the boost
pressure high at low load range,
thereby raising the oxygen
concentration in the combustion
chamber and improving the air
utilization factor. This leads to a
reduction in PM emissions.
NVH performance
The Euro 5 boxer diesel
maintains the NVH standards of
the Euro 4 system while also
satisfying the Euro 5 regulation.
In general, the high
combustion pressure of diesel
engines leads to greater
combustion noise and engine
vibration. The boxer diesel
reduced such NVH and
maximized its potential for
stillness, realizing smooth and
lively driving with low noise
and vibration in all ranges from
idling to high speed, without
Case study: Fuji Heavy Industries
Figure 2 compares the cylinder pressure levels of the two boxer diesel powertrains
Annual Showcase 2010
The second-generation boxer
diesel boasts several new features
including a new DPF system (right)
Figure 1 compares the rate of heat release of the two boxer diesel powertrains
the need for balance shafts. The
combustion noise, which could
have deteriorated by making it
Euro 5 compliant, has been
maintained at the same level as
the Euro 4 system, after
reviewing the number of multistage
injections and calibration
strategies for driving conditions.
The second-generation boxer
diesel has been launched into
the European market, satisfying
the Euro 5 regulation while
maintaining the engine output,
fuel economy, and NVH and
vibration characteristics of the
first-generation engine.
The development of this
engine had two outcomes. First,
five new features have been
introduced: a large-sized EGR
cooler; a new fuel injection; a
new combustion chamber
shape; low compression ratio;
and lift sensors for the actuators
of variable nozzle-type
turbocharger. These features, in
combination with the DPF,
enable the second-generation
boxer diesel to meet Euro 5.
The second outcome is that the
quietness and fuel economy of
the first-generation engine have
been maintained.