mitoban
The New Alfa Romeo Mito

The Alfa MiTo MultiAir

The Alfa Rome MiTo recently adopted a new engine developed by Fiat Powertrain Technologies.

The MiltiAir was initially offered in two turbocharged forms for the UK market - a 135bhp version and a 170bhp unit with a 0-62mph time of just 7.5 seconds and an average fuel consumption figure of 47.1mpg.

The ultimate goal for any engineer is to somehow bring together things which seem incompatible. In the case of Fiat Group’s engine designers, FPT, the seemingly unattainable target has been how to deliver high performance and driveablity while, at the same time, significantly reducing emissions and fuel consumption.

The key to hitting this goal involves 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 that seek to achieve this. But they are 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 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.

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.