Control of fiat multiair valve-lift system using atmega microcontroller

The article presents a device based on the ATmega microcontroller for precise Fiat MultiAir valve-lift system control. The Fiat MultiAir system is the patented electromechanical actuation system of the inlet valves. It allows a control of the inlet valves open time for each combustion chamber independently. The described device has been installed in the Fiat 0.9 TwinAir CNG 80 HP internal combustion engine controlled by the ECU Master open motor controller. As the ECU Master Controller software and hardware does not support Fiat’s MultiAir system control, the above-mentioned device had to be designed. The device consists of the ATmega88 microcontroller, which analyses the signals from the shaft and the cam sensors. Then, the DC converter is powering the solenoid valves of the MultiAir system via two transistors. When the solenoid valve is closed, the incompressible hydraulic fluid transmits the inletcam lobe’s motion to the valve as in a traditional engine. When the solenoid valve is open, the oil bypasses the passage, decoupling the valve, which then closes conventionally via spring pressure. In order to find the specific moments of turning the solenoids on and off the measurements on the original Fiat motor controller have been performed. The acquired oscillograms have been analysed and presented in the article. Studied Fiat 0.9 TwinAir engine is a part of the power generation unit and has been coupled with the three-phase electric power generator MeccAlte 16 kW with an AC exciter.