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Valeo says that its StARS starter/alternator stop/start system
can start diesel engines |
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with displacements as large as 2.0 L and gasoline engines with
displacements over 3.0 L. |
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“It is our role as a
supplier to create the new car which does not pollute as much,”
began Valeo Chairman and CEO Thierry Morin, speaking at the
Frankfurt Motor Show in September. Morin illustrated the point with
projected annual global automobile production figures for 2014—88
million compared with an expected 68 million in 2008, rising to 1.2
billion by 2030. The pressure by governments to reduce carbon
dioxide emissions is therefore irresistible, he thinks.
However, by using a combination
of technologies, Morin believes that Valeo can reduce carbon dioxide
emissions from a 2.0-L 125-kW (168-hp) turbocharged engine by up to
40%. The drawback is that the cost of this technology would add
between €1000 and €1500 to the powertrain cost by 2012. “But,” added
Morin, “OEMs have no choice.”
To achieve Valeo’s claimed 40%
reduction in carbon dioxide emissions, the company calls on a range
of powertrain technical solutions, some already available, others
under development. The largest single reduction is derived from
replacing the conventional cam-driven valvetrain with an
electromagnetically actuated valvetrain (e-valve). The system, which
won the Gold Award in the “Engineering and Advanced Technology”
category at October’s Equip Auto Show in Paris, requires a 42-V
power supply produced by a voltage inverter from the vehicle’s 12-V
system. |
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Valeo claims carbon dioxide emissions reductions of between 15
and 20% with the addition of its electromagnetic valvetrain. |
Paris, requires a 42-V power supply
produced by a voltage inverter from the vehicle’s 12-V system. The
e-valve system can provide cylinder deactivation and infinitely
variable valve timing, which can deliver up to 15% more torque at
low engine speeds. Each valve is controlled by two magnets and a
pair of opposing springs. The magnets, which are placed above and
below an armature plate attached to the valve stem, catch the
armature plate as the plate moves toward the magnet. When the valve
opens, the upper magnet releases the armature. The valve opens as
the upper spring uncoils and the lower magnet catches the armature
plate, compressing the lower spring in the process.
Valve opening is controlled by
the valve control unit (VCU), according to operating requirements.
The VCU is cooled by the engine cooling system. Closure is a reverse
of the opening process. Valves remain closed when the engine is not
running. Valve opening and closing can take place more quickly than
with a cam drive, which helps to reduce pumping losses, while a
throttle air valve is not needed. |
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The system can be applied to
gasoline and diesel engines, with or without turbocharging and with
direct or indirect fuel injection. Valeo claims efficiency gains and
subsequent carbon dioxide emissions reductions of 15 to 20%. A
vehicle equipped with this e-valve technology is scheduled to reach
the market in 2012.
Valeo’s StARS starter-alternator, as fitted to the Citroën C2 and C3
and due to be used on the Smart Fortwo microhybrid drive, can
deliver efficiency improvements of between 6 and 15%. Accordingto
Valeo, the familiar belt drive system is currently capable of
starting gasoline engines with displacements as high as 3.0 L, and
even up to 4.5 L in the Valeo tests. The system can also start
diesel engines with displacements of up to 2.0 L.
Smaller efficiency gains can be
achieved by using a dry double-clutch system, which can provide
smooth shifts for automated manual transmissions without increasing
fuel consumption. Double-clutch systems such as the BorgWarner-based
Volkswagen DSG rely on wet clutches with a consequent loss of
efficiency compared to a manual gearbox. A dry doubleclutch system
should be capable of providing smooth automatic gear changes without
the losses associated with a torque converter automatic. Valeo
claims a 4 to 6% improvement in efficiency.
Similar reductions can be
provided by an electronically operated coolant flow control valve
and a cooled exhaust-gas recirculation system.
John Kendall, with contributions
from Ryan Gehm
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