Under low-rev conditions the low- and mid-lift cam lobes drive the intake valves, providing slightly better fuel economy and lower emissions. This also means that the cam switch operation is virtually transparent to the driver, who is simply rewarded with more power. More precisely, MIVEC switches to the higher cam profile at 3600 rpm as engine speed increases, and drops back to the lower cam profile at 3400 rpm as engine speed decreases the output torque of the low- and high-speed modes overlap at those speeds. The switch occurs at approximately 3500 rpm, when the powertrain control module opens the valves longer to increase the amount of intake airflow, resulting in higher engine output. The high-lift cams' T-shaped levers are then able to directly contact the elevated rocker-arm pistons, overriding the low-speed cam lobes and fully controlling intake-valve lift and duration.īETTER PERFORMANCE AT THE FLIP OF A SWITCH At high engine speeds, the pistons within the rocker arms elevate when MIVEC sends increased oil pressure through an oil control valve. The high-speed mode opens the valves longer due to its higher lift. The benefit of the dual-profile low-speed mode is to induce swirl within the cylinder, which help create stable combustion and improve emissions. The intake rocker arms contain internal pistons that are retained by springs in a lowered position at less than 3500 rpm, to avoid contacting the high-lift T-shaped levers. The high-lift cam is directly connected to a T-shaped lever, which controls valve lift and duration of both intake valves in the high engine-speed mode.Īt lower engine speeds, the T-shaped levers connected to the high-lift cams reciprocate freely without contacting intake-valve rocker arms, thus allowing the low- and mid-lift cam lobes to control corresponding intake-valve lift and timing. The low- and mid-lift cams and rocker arms - which drive separate intake valves - are positioned on either side of a centrally located high-lift cam. In the MIVEC system, there are three distinct cam profiles that create two engine modes: a low-speed mode, consisting of low- and mid-lift cam profiles and a high-speed mode. The enhanced power output of the MIVEC system is achieved by its ability to vary the lift and duration of the intake valves.
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But when the throttle is opened wide and engine speed increased, MIVEC allows the valves a longer duration and longer stroke, thus providing maximum and efficient power and torque over a broader range of engine speeds.
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Under low-rev conditions, MIVEC selects the smaller cam profile, which provides stable combustion and lower emissions. The MIVEC system features separate cam profiles for high and low engine speed modes, which translates to higher maximum power and increased usable torque in the widest variety of driving conditions. The 2.4-liter SOHC four-cylinder engine found in the 2004 Mitsubishi Lancer Ralliart, Lancer Sportback and Outlander utilizes advanced Mitsubishi Innovative Valve timing and lift Electronic Control (MIVEC) system technology to improve power output over a wide rpm range without sacrificing emissions or fuel economy in the process.