Fiat launches new MultiAir engines

By Tim Pollard

Motor Industry

09 March 2009 14:02

Fiat showed off the detail of its new MultiAir engines at the 2009 Geneva motor show – and we’ll finally be able to buy the tech on the new Alfa Romeo Mito supermini later in 2009. The brains behind the common-rail injection system that shook up diesel technology have now produced a new technology designed to make petrol engines more efficient and cleaner.

Engineers claim the MultiAir engines – which use electrohydraulic actuation, rather than the more widely available electromechanical systems – boost power and torque, while cutting CO2 by between 10% and 25% and other pollutants by up to 60%. The secret? Using electronic actuation and control of the intake valves to make the passage of air into and out of the cylinders more efficient.

Fiat’s new system uses intake valves operated by a conventional valve spring – but, crucially, they can be overridden by the MultiAir pack. A piston is attached to each intake valve through an hydraulic chamber; the chamber is controlled by an on/off solenoid valve – determining whether intake is governed by the conventional camshaft or the electronics.

Under maximum power, the solenoid valve is shut and the engine runs off the mechanical camshaft, which is calibrated for a long opening time and extra power. But MultiAir can then tweak intake performance on each cylinder for low-revs torque or part-load conditions.

Fiat claims its system is more flexible than the electromechanical variable valve lift systems used by companies such as Honda and BMW, which struggle to offer individual cylinder control, it claims.

The new valvework will appear this autumn on the Mito, on a new family of 16-valve 1.4-litre naturally aspirated and turbocharged engines. Next up is Fiat’s radical new two-cylinder engine family under development for future group small cars.

The next generation of MultiAir engines will be mated to direct injection and Fiat claims the tech can be rolled out to alternative-fuel engines too, including those powered by natural gas, hydrogen and biofuels.

By Tim Pollard