Motoring News

The Alfa Romeo MiTo is already a global success story. Sold in 34 countries and on five different continents, it has won wide acclaim for its unprecedented fusion of head-turning high end style, engineering flair, dynamic performance and driving pleasure.

And now, Alfa has moved the game on again, bringing revolutionary MultiAir technology and a raft of technical innovations to the world’s sportiest compact car. The evolution underlines the company’s on-going commitment to reconcile lower emissions and fuel consumption with higher performance and driver satisfaction for an increasingly extensive, smart and environmentally aware audience.

The new Euro 5-ready 1.4-litre MultiAir engine, developed and patented by Fiat Powertrain Technologies (FPT), made its international debut in the MiTo late last year, and is initially offered in two turbocharged forms for the UK market. The 135bhp version of the unit powers the £15,165 Lusso and £16,135 Veloce, while the range-topping £17,895 Cloverleaf – an auspicious return for the iconic badge close to every Alfista’s heart – boasts 170bhp and a 0-62mph time of just 7.5 seconds, but a combined fuel consumption of 47.1 mpg.

In addition to MultiAir, the new MiTo range showcases a broad spectrum of innovative technologies, including active suspension on the Cloverleaf (a first for this class of car), the emission-reducing Start&Stop system across the range, and Alfa Romeo DNA. Derived from racing, this three-mode electronic system communicates with the engine, brakes, steering, suspension (on MiTo Cloverleaf), and transmission, allowing the driver to adjust the responses of the car to suit driving style and road conditions.  

Alfa’s Electronic Q2 limited slip differential heads a number of dynamic driver aids, including a long list of safety systems. Together with the MacPherson strut/torsion beam suspension layout, these all help deliver the handling dynamics and sure-footed road holding capabilities you’d expect from an Alfa, whatever the road. Designed to satisfy the highest Euro NCAP crash safety rating, the MiTo also offers optimum passive safety.

The model’s high level of engineering integrity can also be appreciated through the series of improvements that have further increased the quality of the Alfa MiTo. Improvements embrace the interior finish, trim combinations, and gearchange quality (the lever on the MiTo Cloverleaf has been shortened by 2.5 centimetres) as well as modifications to the steering, suspension and braking systems.

WHY MULTIAIR?

The Holy Grail for any engineering endeavour is to have your cake and eat it – to unify seemingly incompatible goals. For the Fiat Group’s engine designers, FPT, the quest has been clear cut: how to deliver high performance and driveablity while, at the same time, significantly reducing emissions and fuel consumption.

The key to achieving this is well understood. It requires taking more precise control of the quantity and characteristics of the air drawn into the cylinders in the combustion cycle. There are numerous electro-mechanical variable valve timing systems in production today that seek to achieve this. But because they usually have only two operating regimes, they are severely limited by the degree of flexibility they can exercise in the valve opening schedules.

MultiAir eliminates these compromises by metering the direct air charge at the cylinder inlet ports with an advanced electro-hydraulic actuation and control system that has no fewer than five basic parameters, and the ability to optimally adjust valve timing and lift between them to exactly suit different engine speeds and loads, ensuring strong low- and mid-range torque and vigorous top-end power, combined with good economy and low emissions.

This is a transformational technology comparable to the introduction of FPT’s common rail fueling for diesels, but the principles behind it are as simple as they are ingenious. MultiAir engines have just one camshaft with three lobes allocated to each cylinder. The first two control the two exhaust valves in the conventional way, while the third defines the maximum possible lift and opening duration of the two inlet valves. It also acts on a small piston that sends engine oil, via pressurised hydraulic channels, to additional pistons located just above the inlet valves.

Four solenoid valves – one for each cylinder under individual control from the Magneti Marelli ECU engine management system – can be opened at any point during the inlet valve’s movement to bleed off the oil. Varying the oil flow instantly and precisely controls the opening and closing of the valves between the parameter extremes mechanically described by the camshaft lobe for optimum results.

MultiAir can even open the inlet valve twice in one intake stroke, when running at low speeds and loads around town, to create more swirl of the intake mixture, enabling it to burn more completely.

MultiAir strategies

When the solenoid valve is closed, the oil in the hydraulic chamber behaves like a solid body and acts on the intake valves in accordance with the profile of the cam lobe.
When the solenoid valve is open, the hydraulic chamber and the intake valves are de-coupled; the valves no longer follow the cam profile.
By controlling the solenoid closing period, various optimal intake valve opening schedules can be realised.
MULTIAIR IN ACTION

Different strategies can be employed to optimise combustion efficiency, according to varying driving situations -

FULL LIFT – for maximum power, the Solenoid Valve is always closed and full valve opening is achieved by completely following the mechanical cam, which was specifically designed to maximise power at high engine speed; i.e: motorway driving.

EIVC (Early Intake Valve Closing)- 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; i.e: during acceleration.

LIVO (Late Intake Valve Opening) – 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.

PARTIAL LOAD – 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; i.e: at engine start up or idling.

MULTI-LIFT – Multiple opening strategies are used to enhance turbulence and combustion rate at very low loads. The advantage is a significant reduction in fuel consumption and emissions in the urban cycle; i.e: city driving.

MultiAir makes the difference: 1.4 TB MultiAir 135bhp compared to the 1.4 TB 120bhp

CO2 reduced by over 10%
Max power increased by 12.5%
Acceleration (0-62mph) reduced by up 0.4 seconds
Better throttle response, less turbo lag
Fuel consumption reduced by up to 10% 

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