MIVEC

From Wikipedia, the free encyclopedia

MIVEC™ (Mitsubishi Innovative Valve timing Electronic Control system)^[1] is the brand name of a variable valve timing engine technology developed by Mitsubishi Motors. MIVEC, as with other similar systems, varies the lift of the valves by using two different camshaft profiles. At low speeds, a mild (low-lift) cam lobe provides "normal" performance, 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 output.

MIVEC was first introduced in 1992 in their 4G92 powerplant, a 1,597 cc naturally aspirated DOHC 16 valve straight-4.^[2] 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,^[3] the MIVEC-equipped engine could achieve 175 PS at 7500 rpm.^[4] 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.^[5] The GR model, whose otherwise identical powerplant was not MIVEC-equipped, produced 170 PS at 7000 rpm by comparison.^[6]

Although initially design 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. Many implementations only vary the valve timing (the amount of time per engine revolution that the intake port is open) and not the lift.

[edit] MIVEC-MD

In the early years of developing its MIVEC technology, Mitsubishi also introduced a variant dubbed MIVEC-MD (Modulated Displacement),^[7]^[8] a form of variable displacement. Under a light throttle load, the intake and exhaust valves in two of the cylinders would remain closed, and the reduced pumping losses gave a claimed 10–20 percent improvement in fuel economy. Modulated Displacement was dropped around 1996.^[7]

[edit] Current implementations

Engine code	Capacity	Configuration	Year
3A91	1124 cc	Straight-3	(2003–present)
3B20	659 cc	Straight-3	(2005–present)
4A90	1332 cc	Straight-4	(2003–present)
4A91	1499 cc	Straight-4	(2003–present)
4B11	1998 cc	Straight-4	(2007–present)
4B12	2359 cc	Straight-4	(2005–present)
4G15	1468 cc	Straight-4	(2003–present)
4G19	1343 cc	Straight-4	(2002–present)
4G63T	1997 cc	Straight-4	(2005–present)
4G69	2378 cc	Straight-4	(2003–present)
6B31	2998 cc	V6	(2006–present)
6G75	3828 cc	V6	(2005–present)