Volvo Cars' Diesel Engine Overview
- Improved performance and lower emissions
- Larger, electronically controlled
turbocharger
- Improved fuel-injection system
- More powerful engine management system
- More efficient EGR system
- Maintenance-free particulate filter
- Six-speed automatic gearbox
- All Wheel Drive with Instant Traction for
XC90
- Class leading fuel efficiency - 9L/100km
The Volvo Car Corporation in 2005 unveiled a new generation of
its own five-cylinder diesel engine. The five-cylinder engine has
been extensively improved and refined and debuts in Australia in
the XC90 D5.
The result is an improved engine with a new driving character
offering considerably higher performance and improved drivability.
At the same time, there is a sharp reduction in tailpipe
emissions.
This new diesel engine is offered in Europe at three power
outputs. However, Australia will see only the most potent variant -
the 136kW, 400Nm D5.
Via several technical improvements, the D5 engine produces an
additional 16kW to achieve a maximum output of 136kW. The increase
provides excellent high-speed performance with responsive
acceleration and efficient pulling power.
Torque improves dramatically from 340Nm to 400Nm, and the D5
engine is easily capable to pushing the large XC90 with impressive
urgency. Low rev engine response is considerably improved and the
D5 engine revs willingly to 5000rpm.
"We have improved nearly everything in the engine," says
Jörgen Svensson, Chief Program Engineer. "The driver will
perceive it as a lively petrol engine, only more powerful and more
environmentally efficient."
New-generation turbocharger
The new-generation turbocharger is electronically controlled to
achieve precise control of charge pressure. A larger compressor
wheel provides higher torque and output. Furthermore, the variable
vanes have been cambered for a more efficient flow of gas at all
compressor speeds, resulting in an increased level of turbo
efficiency. The improvements contribute to faster acceleration and
better high-speed performance.
The turbocharger's centre bearing housing is now water-cooled,
which is unusual in diesel engines. Water cooling is necessary
because of the higher performance of the new engine and provides
continued cooling of the turbocharger after the engine has been
switched off. This is particularly beneficial during short stops
after high-speed driving.
Refined injection technology
The use of a new electronically controlled multi-throttle system in
the inlet ports allows for infinitely variable regulation of the
swirl level, and combustion can be adjusted extremely accurately
according to the driving situation and the current engine speed and
load.
"We have also made the combustion chambers larger, thereby
lowering compression," says Svensson. "By doing so, we have gained
two things: higher performance and lower emissions."
The injection system now uses new injectors with seven finer
nozzle openings as opposed to five in the previous engine. This
results in a more finely atomized fuel mixture and more efficient
combustion. Injection takes place in three steps: pre-injection,
primary injection, and post-injection. The injection phase is new
and contributes to cleaner combustion and also to regeneration of
the particulate filter.
A completely new, electronically regulated quick glow system
results in considerably reduced glow times, also making it easier
to start the engine in cold weather.
New management system contributes to reduced
emissions
The new diesel engine has very low emissions, thanks to a number of
new and refined functions. For example, emissions of nitrogen
oxides (NOx) have been halved.
A new-generation engine management system, with increased
capacity and a greater number of sensors, offers more accurate
control of the engine's functions. This includes electronic control
of the throttle and the new, more powerful EGR (Exhaust Gas
Recirculation) valve for more precise regulation of the air supply
and recirculation of exhaust gases.
"We also have a completely new EGR cooler," says Svensson. "This
lowers the combustion temperature very efficiently, thereby
reducing emissions."
The catalytic converter is now fitted nearer to the engine to
promote faster warming and thus faster startup of the exhaust
cleaning process. The catalytic converter is also larger than
before. In addition it has been supplemented with an oxygen sensor
that precisely regulates the fuel mixture and emissions.
Particulate filter is standard
Volvo's new diesel engine has a particulate filter as standard
equipment. It very effectively removes soot particulates from the
exhaust gases, with filtration efficiency above 95 percent. The
filter is a CDPF - Coated Diesel Particulate Filter - in which a
special coating helps burn the particulates. Therefore, no
additives are needed, and the filter requires no maintenance.
Burning away soot particulates takes approximately 20 minutes and
occurs automatically at 500km to 1000km intervals, depending on
driving conditions.
Six-speed automatic gearbox
A standard pairing, the D5 engine combines with a six-speed
automatic to accommodate the engine's high torque loads. The six
speeds contribute to sportier driving and improved NVH.
The new six-speed automatic transmission contributes to the
model-year XC90's agility and refinement. The engine's broad torque
curve works in harmony with the quick shifting automatic to achieve
quite impressive throttle response at nearly all engine and vehicle
speeds. In particular, the gearbox is able to kick down without
delay.
The torque converter features a lock-up that is allowed to slip
over a wide range of engine speeds for effective pulling power and
good drivability, particularly when transporting heavy loads or
towing a caravan.
All Wheel Drive with Instant Traction
The improved AWD system with Instant Traction, which was introduced
on the Volvo XC90 V8, is now combined with the D5 diesel engine.
Instant Traction makes starting easier on slippery surfaces by
immediately distributing the right amount of power to the rear
wheels the instant the car starts to move.
"The D5 engine with a six-speed gearbox and All Wheel Drive is a
nearly unbeatable combination," says Svensson. "It offers enormous
driving pleasure while also providing power and low-rpm capacity
for the most demanding uses."
Summary
Most of the measures taken on Volvo's new diesel engine result in
an increase in performance and reduced emissions. The primary
purposes are explained in the following summary:
For increased performance
- The injection system has been improved with new injectors and a
more advanced injection process
- A new-generation turbocharger, with larger compressor wheel,
cambered vanes and electronic control
- The gas exchange system has been upgraded for optimum flow of
air and exhaust gases, with low pressure losses
For lower emissions
- A new-generation engine management system with a greater number
of sensors for more precise regulation
- The EGR (Exhaust Gas Recirculation) system is new, with faster
regulation of the flow
- The EGR cooling is new with higher capacity
- The air throttle is new and electronically controlled in order
to more effectively control EGR flow, reduce noise and regulate the
temperature
- Air swirl in the combustion chamber is infinitely variable for
more efficient combustion
- The lowered compression ratio (from 18:1 to 17:1) with new and
larger combustion chambers lowers compression temperatures and
reduces emissions
- The quick glow system is new and electronically controlled for
faster cold starts
- The catalytic converter is larger and fitted with an oxygen
sensor for precise emission control
- The Coated Diesel Particulate Filter (CDPF) is standard on all
versions