Fiat Powertrain
Technologies (FPT) has started manufacturing of the
1.4-litre FIRE engine incorporating the ground-breaking new
Multiair electro-hydraulic value actuation system ahead of
its introduction into Fiat Group Automobiles' production
models starting from September. The news that Multiair
pre-production is now getting underway at FPT's key Termoli plant at
Molise in Italy comes from the Milano Finanza newspaper.
Termoli is one of
FPT's key factories and currently produces the 1.4-litre
FIRE engine, in 8v and 16v formats, as well as manufacturing
Fiat's C510, C513 and C546 transmissions. The highly
advanced Multiair system was officially presented during a
press conference at the 79th Geneva Motor Show in March, and
its first application will be on the Alfa Romeo MiTo in the
autumn. It will be initially fitted to a range of 1.4-litre
engines with power outputs from 105 to 170 bhp before being
rolled out to a number of other FPT range engines next year,
including the forthcoming 900c SGE (Small Gasoline Engine).
Alongside Multiair,
FPT will also introduce its Multijet 2 technology later this year
on the acclaimed 1.3 SDE. The new technology, focusing mainly around
developments in pump and injector technology, will boost the engine's outputs
from the current 90bhp and 200Nm to 95bhp and 230Nm, and is expected to debut in
the Lancia Musa before also appearing in the Fiat 500.
Multiair is a new
electro-hydraulic system of engine valves for dynamic and
direct control of air and combustion, cylinder by cylinder
and stroke by stroke. Thanks to a direct control of the air
through the intake engine valves without using the throttle,
Multiair helps reducing fuel consumption; pollutant
emissions are likewise reduced through combustion control
Multiair is a versatile technology, easily applicable to all
gasoline engines and with future potential developments also
for diesel engines.
The multiple
benefits of the Mutiair system start with an increase of maximum power
by up to 10 percent thanks to the adoption of a
power-oriented mechanical cam profile. Low-rpm torque is
improved by up to 15 percent through early intake valve
closing strategies that maximize the air mass trapped in the
cylinders. Elimination of pumping losses brings a 10 percent
reduction of fuel consumption and CO2 emissions, both in
naturally aspirated and turbocharged engines with the same
displacement. Multiair turbocharged and downsized engines
can achieve up to 25 percent fuel economy improvement over
conventional naturally aspirated engines with the same level
of performance. The Multiair system also offers optimum valve control
strategies during engine warm-up and internal exhaust gas
recirculation, realised by reopening the intake valves
during the exhaust stroke, result in emissions reduction
ranging from 40 percent for HC / CO to 60 percent for NOx.
The operating
principle of the Multiair system, applied to intake valves,
is the following: a piston, moved by a mechanical intake
cam, is connected to the intake valve through a hydraulic
chamber, which is controlled by a normally open on/off
solenoid valve. When the solenoid valve is closed, the oil
in the hydraulic chamber behaves like a solid body and
transmits to the intake valves the lift schedule imposed by
the mechanical intake cam. When the solenoid valve is open,
the hydraulic chamber and the intake valves are de-coupled;
the intake valves do not follow the intake cam anymore and
close under the valve spring action. The final part of the
valve closing stroke is controlled by a dedicated hydraulic
brake, to ensure a soft and regular landing phase in any
engine operating conditions. Through solenoid valve opening
and closing time control, a wide range of optimum intake
valve opening schedules can be easily obtained. For maximum
power, the solenoid valve is always closed and full valve
opening is achieved following completely the mechanical cam,
which was specifically designed to maximise power at high
engine speed (long opening time). For low-rpm torque, the
solenoid valve is opened near the end of the cam profile,
leading to early intake valve closing. This eliminates
unwanted backflow into the manifold and maximises the air
mass trapped in the cylinders. In engine part load, the
solenoid valve is opened earlier causing partial valve
openings to control the trapped air mass as a function of
the required torque. Alternatively the intake valves can be
partially opened by closing the solenoid valve once the
mechanical cam action has already started. In this case the
air stream into the cylinder is faster and results in higher
in-cylinder turbulence. The last two actuation modes can be
combined in the same intake stroke, generating a so-called
“Multilift” mode, that enhances turbulence and combustion
rate at very low loads.
