Fiat Unveils New Low CO2 Multiair Engine in Geneva

Fiat has unveiled new MultiAir 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

With two generations of common rail direct injection diesel engine technology, UniJet and MultiJet, to its credit, Fiat has dramatically improved diesel engine performance, economy and emissions.

Now, with MultiAir launched at Geneva Motor Show, Fiat has brought together the company’s enviable expertise and technology to make one of the single largest leaps forward for petrol engine design in recent times.

MultiAir Technology benefits:

 - Maximum power is increased by up to 10 percent thanks to the adoption of a power-orientated mechanical camshaft 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 in 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.
 - Optimum valve control strategies during engine warm-up and internal exhaust gas recirculation, realized 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 engines, regardless of the fuel used.
 - It can be adapted for diesel engines to reduce their NOx emissions and make particulate filters significantly more effective.

In short, an engine equipped with Fiat MultiAir technology is more powerful, more responsive across the entire engine speed range, uses considerably less fuel, and reduces all types of exhaust emissions by a substantial amount.

It will also assist in enabling Fiat to maintain its lead in low emissions and low fuel consumption technology, which has seen Fiat crowned for the past two years as the number one car maker for the lowest range-wide CO2 emissions.

The first new engine to be equipped with MultiAir will be the 16-valve 1.4 liter family of naturally aspirated and turbocharged engines, and the first car to go on sale with MultiAir installed will be the Alfa MiTo at the end of 2009. Its second application will be as an integral part of a new two cylinder engine family.

Fiat MultiAir Technology: how it works

The operating principle of the system, applied to intake valves, is the following: a piston, moved by a mechanical intake camshaft, 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 camshaft.

When the solenoid valve is open, the hydraulic chamber and the intake valves are de-coupled; the intake valves do not follow the intake camshaft 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 camshaft, which is specifically designed to maximize power at high engine speed (long opening time).

For low-rpm torque, the solenoid valve is opened near the end of the camshaft profile, leading to early intake valve closing. This eliminates unwanted backflow into the manifold and maximizes 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 camshaft 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.

Check out the rest of our Geneva Motor Show coverage.