Damiano Michelli, and engineer at Alfa Romeo’s FIAT Powertrain Technologies explains the MultiAir unit that will find its way under the valve cover of the 170 HP version of the 1.4 Liter MiTo.
The MultiAir system eliminates the need for a throttle body and allows the engineers infinite control over the valves that bring fresh air into the combustion chamber. The design places the lobes for both intake and exhaust on the same camshaft. The exhaust operates as it would in a convention four stroke internal combustion engine, but the third bump actuates a roller rocker arm attached to the MultiAir setup which is then electronically controlled to open and close the intake valve by the flow of pressurized engine oil.
The idea is similar to other automakers variable valve timing systems, except that MultiAir can adapt to any situation and individually tune each cylinder if necessary. The FPT unit not only allows the ECU the intake valve lift and duration, but also throw in a couple tricks like: late intake valve opening when sitting at idle, early intake valve closing for a more complete burn of the fuel soaked charged and there is even a multi lift function that brings fresh air into the combustion chamber at multiple points in the engine’s cycle ensuring minimal waste and to maximize the efficiency of the intake charge.
Overall, MultiAir equipped engines benefit from a 10% reduction in CO2 emissions, 10% more power and a 15% torque improvement; but mainly a much more dynamic driving experience. Just like direct fuel injection, the system is more efficient than a conventional internal combustion engine and at the same time makes more power.