MIVEC (Mitsubishi Innovative Valve timing Electronic
Control system)is the brand name of a variable valve
timing engine technology developed by Mitsubishi Motors. MIVEC, as
with other similar systems, varies the timing, lift and duration[2]
of the valves by using two different camshaft profiles. At low
speeds, a mild (low-lift) cam lobe provides stable idle, lower
emissions and increased torque at lower speeds, while above a fixed
engine speed a second set of cam lobes are activated, providing
higher lift and duration; therefore a greater quantity of air into
the combustion chamber which increases the power and torque output
over a broad engine speed range.
From 4B1 engine family onward, MIVEC has fully evolved into a
continuous variable valve timing system (dual VVT on intake and
exhaust valves). [3] MIVEC incorporated in 3B2, 3A9 and 4A9 engine
family continuously varies only the intake valves. Many older
implementations only vary the valve timing (the amount of time per
engine revolution that the intake port is open) and not the
lift.
MIVEC was first introduced in 1992 in their 4G92 powerplant, a
1,597 cc naturally aspirated DOHC 16 valve straight-4.[4] At the
time, the first generation of the system was named Mitsubishi
Innovative Valve timing and lift Electronic Control.[5] The first
cars to use this were the Mitsubishi Mirage hatchback and the
Mitsubishi Lancer sedan. While the conventional 4G92 engine
provided 145 PS at 7000 rpm,[6] the MIVEC-equipped engine could
achieve 175 PS at 7500 rpm.[7] Similar improvements were seen when
the technology was applied to the 1994 Mitsubishi FTO, whose
top-spec GPX variant had a 6A12 1997 cc DOHC 24 valve V6 with peak
power of 200 PS at 7500 rpm.[8] The GR model, whose otherwise
identical powerplant was not MIVEC-equipped, produced 170 PS at
7000 rpm by comparison.[9]
Although initially designed to enhance performance, the system has
subsequently been developed to improve economy and emissions, and
has been introduced across Mitsubishi's range of vehicles, from the
i kei car to the high-performance Lancer Evolution sedan.
