# Review of Advancement in Variable Valve Actuation of Internal Combustion Engines
## 6 Lost-Motion VVA (LMVVA)  
Various lost-motion systems were disclosed in many patents, for example, US 4671221, US 5193494, US 5839400, US 6053136, US 653950, US 6918364, US 681476, US 7819100, US 8578901, US 8820276, US 8776738, and US 9625050.  
Fiat Powertrain Technologies and Schaeffler Group developed the only mass production systems branded as MultiAir and UniAir, respectively, which were first launched at the 2009 Geneva MotorShow in the Alfa Romeo MiTo and were licensed in 2017 to Jaguar Land Rover for its Ingenium engine family.  
In the MultiAir system, a solenoid valve controls the hydraulic pressure in a passageway connecting the intake valves and the camshaft [27]. The solenoid valve regulates the amount of oil that is pumped by the cam action either to the valve or a bypass reservoir. When pressurized, the hydraulic line behaves like a solid body and transmits the lift schedule imparted by intake cam directly to the intake valve in the full valve lift mode for max power. When the solenoid is disengaged, a spring takes over valve actuation, losing solid transmission of the motion from the cam in other three modes, which are the early intake valve closing mode, the late intake valve opening mode, and the multi-lift mode, thus leading to the name lost motion. This electro-hydraulic link allows independent operation of the two components, resulting in certain control over the valve lift profiles. A closed solenoid keeps the hydraulic fluid pressurized, transmitting the intake cam profile to the valve in the normal fashion, while an open solenoid breaks the effective link between cam and valve, decoupling their profiles [27].  
This system is not a full VVA system because the valve timing and duration are not independent of the lift in each of the three lost-motion modes although one has a choice to choose three different dependencies, i.e., variability or control flexibility, among these three modes. The intake valve opening event cannot be shifted ahead or left of that at maximum power, which may be necessary for certain EGR operations. Also, the intake valve closing event cannot be extended beyond or right of that at maximum power, which may be necessary for certain Miller cycles.  
Jacobs Vehicle Systems Inc. also developed its own version of the lost-motion VVA system, with emphasis on diesel engine efficiency and after-treatment optimization [57]. It includes the capability of on-off control of secondary events for IEGR and engine braking, high load capacity for early exhaust opening and engine braking, and inherent protection against valve-to-piston contact.  
More recently, there were efforts by Gongda Power [58] and Shandong University [59] to replace solenoid valves for individual actuators with motor-driven rotary valves common to a group of actuators, to achieve more stable and faster time response at low temperature and/or to devise an alternative hardware, but at the cost of losing independent controllability for individual actuators within a group. The Gongda Power system [58] uses two motor-driven rotary valves, instead of just one valve by Shandong University [59], to add control flexibility to achieve the Miller cycle by enabling much later intake valve closing to reduce pumping loss and lower air temperature. It can also incorporate a special cam lobe to achieve earlier exhaust valve opening and, thus, compression brake function for a diesel engine.