The MCA stands for Mitsubishi Clean Air which meant that the EX passes both Japan and US emission standards whilst the new cylinder head design of the engine gave way for a third or Jet valve that introduces an extra swirl of air to the combustion chamber swirling the fuel-air mixture for a cleaner, efficient and thorough burn. Another new breakthrough in the Lancer is the Silent Shaft Technology which is actually two counterbalancing shafts that rotate in opposite directions, cancelling the power pulses a normal 4 cylinder engine would be inherent back then, reducing engine noise and vibration providing a smoother ride.
