2. ABSTRACT
Downsizing and turbo charging in
combination with UNIAIR electronic valve
control and gasoline direct injection are
now commonly regarded as key
technologies for SI engines to cope with the
challenges of fuel economy enhancement
and driveability improvement.
The Multiair technology is an innovative
system for intake valves electronic control
which, by regulating the intake air at every
combustion cycle, allows both a substantial
consumption reduction and a remarkable
3. Introduction
• Multiair is a fundamental breakthrough in
petrol engine design that will dramatically
cut fuel consumption, as well as
significantly boosting power and torque,
cutting carbon dioxide emissions by
between 10 and 25 percent, and up to a 60
percent reduction in other engine
pollutants.
• This higher output will allow Fiat to replace
larger engines with smaller, more efficient
ones, and the company's 1.0 liter and 1.4
liter engines will be the first to get the new
5. MULTI AIR TECHNOLOGY EXPLAINED
The beauty of Fiat’s “Multiair” system is its
simplicity; it essentially achieves what
Valvetronic does by using hydraulic fluid
running through narrow passages connecting
the intake valves and the camshaft so the two
can be decoupled.
This system is modulated by an electronically
controlled solenoid, and there are effectively
two modes:
When the solenoid is closed, the
incompressible hydraulic fluid transmits the
intake-cam lobe’s motion to the valve, as in a
traditional engine.
6. MULTI AIR TECHNOLOGY EXPLAINED
For example, to shut the valves early, as in a
part-load situation, the solenoid would be
closed initially and then open partway through
the intake cycle.
The tricky business is correctly timing the
switching of the solenoid, and Fiat has
painstakingly optimized the responsiveness of
the electronic controls.
Aside from the fuel-economy and emissions
benefits, Fiat claims Multiair can also enable a
10-percent horsepower boost.
13. Features
The application of the Multiair technology offers
the potential to improve almost all the critical
areas of SI engines:
Throttleless load control reduced fuel
consumption
Optimal charge trapping efficiency increased
performance
Fast and direct valve control improved
dynamic response and fun to drive
Advanced combustion control reduced fuel
consumption and emissions
Performance and driveability increase potential
is significant, thanks to:
Torque and power increase, due to optimal
volumetric efficiency over the whole engine
15. Benefits
• Maximum power is increased by up to 10 per
cent thanks to the adoption of a power-
orientated mechanical camshaft profile.
• Low RPM torque is improved by up to 15 per
cent through early intake valve closing
strategies that maximise the air mass trapped
in the cylinders.
• Elimination of pumping losses brings a 10 per
cent reduction in fuel consumption and CO2
emissions, both in naturally aspirated and
turbocharged engines with the same
displacement.
• MultiAir turbocharged and downsized engines
16. Benefits
• 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 reductions
ranging from 40 per cent for unburnt
hydrocarbons and carbon monoxide (HC/CO), and
up to a 60 per cent cut in oxides of nitrogen,
(NOx).
• Constant upstream air pressure, atmospheric for
naturally aspirated and higher for turbocharged
engines, together with extremely fast air mass
control, cylinder-by-cylinder and stroke-by-stroke,
result in a superior dynamic engine response, and
enhanced driving pleasure.
• MultiAir is applicable to all internal combustion
17. Summary
• The beauty of “Multiair” system is its
simplicity; it essentially achieves what
Valvetronic does by using hydraulic fluid
running through narrow passages connecting
the intake valves and the camshaft so the two
can be decoupled.
This system is modulated by an electronically
controlled solenoid, and there are effectively
two modes:
• When the solenoid is closed, the
incompressible hydraulic fluid transmits the
intake-cam lobe’s motion to the valve, as in a
traditional engine.
18. Summary
• For example, to shut the valves early, as in a
part-load situation, the solenoid would be
closed initially and then open partway through
the intake cycle.
• The tricky business is correctly timing the
switching of the solenoid, and Fiat has
painstakingly optimized the responsiveness of
the electronic controls.
• Aside from the fuel-economy and emissions
benefits, it is claimed that Multiair can also
enable a 10-percent horsepower boost.
19. Summary
• Components of 4WD vehicles can be
serviced in basically the same manner as
the same components on a 2WD vehicle.
• Some AWD vehicles have a third
differential, called an interaxle differential,
instead of a transfer case.
