2008 Alfa Romeo MiToEnlarge Photo
Compared to a traditional petrol engine with the same displacement, MultiAir engines ensure an increase in power (up to 10%) and torque (up to 15%), as well as a considerable reduction in consumption levels (up to 10%) and CO2 emissions (up to 10%), of particulates (up to 40%) and NOx (up to 60%).
The technology will first appear in MiTo models powered by a 1.4L petrol engine and will be offered with three different power levels (105hp, 135hp and 170hp).
The heart of the MultiAir is the new electro-hydraulic valve control system which makes it possible to reduce fuel consumption and polluting emissions. The key to controlling petrol engine combustion, and therefore performance, emissions and fuel consumption, is the quantity and characteristics of the fresh air charge in the cylinders. In conventional petrol engines the air mass trapped in the cylinders is controlled by keeping the intake valve opening constant and adjusting upstream pressure through a throttle valve and camshafts.
One of the drawbacks of this simple conventional mechanical control is that the engine wastes about 10% of the input energy in pumping the air charge from a lower intake pressure to the atmospheric exhaust pressure.
MultiAir is unique in that it uses an electro-hydraulic system to actuate the valves as opposed to the more common electro-mechanical setup. This relatively simple system can alter the timing of the valve's opening and closing in relation to how much power or efficiency is required at any specific moment. Additionally, it draws very little power from the engine. For more information, check out our previous story by clicking here.