General Description
GENERAL DESCRIPTION4G69 engine used in OUTLANDER adopts MITSUBISHI INNOVATIVE VALVE TIMING & LIFTING ELECTRONIC CONTROL SYSTEM (MIVEC).
MIVEC mechanism is as follows:
MITSUBISHI INNOVATIVE VALVE TIMING & LIFTING ELECTRONIC CONTROL SYSTEM (MIVEC)
MIVEC adopts the additional switching system on the two intake valves in the conventional SOHC 4 valve engine. This switching system has the two cams that are for the low mode having the difference between the valve lifts and for the high mode keeping the both valve lifts high. In the range of the low engine speed, the flow within the valve is enhanced by the difference between the valve lifts. Also the stabilization of the combustion is designed to realize the low fuel economy, low exhaust gas and high torque. In the range of the high engine speed, the high output due to the increment in the intake air amount is reached by increasing the open valve period and the lift
The structure has the T-lever that moves following the high lift cam and is arranged between the high lift cam and the lift cams of low & middle, in addition to the low & middle lift cams and the rocker arm that drive the two intake valves each. In the range of the low engine speed, the each valve drives alone at the low lift cam and the middle lift cam respectively because the wing of T-lever does not reach the piston. In the range of the high engine speed, the oil pressure moves the piston within the rocker arm. T-lever pushes the rocker arm forward and then the high lift cam drives the both valves.
The cam switching is carried out when the torque to be produced in the low speed mode and the high speed mode respectively is crossing each other at the engine speed of 3500 r/min. An accumulator is mounted to ensure the oil pressure at the instant of switching and to prevent the switching mistakes.
The oil passage is divided into two in just front of the Oil Control Valve (OCV) and lubrication oil is always supplied to the exhaust rocker shaft. Supplying the lubrication oil to the intake rocker shaft is controlled by ON/OFF of the OCV and carries out the switching for the low, middle and high lift cams.
Under the OCV is in OFF position, the switching piston does not operate because the switching oil pressure within the intake rocker shaft is below the specified pressure, and so the wing of the high speed rocker arm does not reach the switching piston. Accordingly, the intake valve is driven by the low speed rocker arm.
Under the OCV is in ON position, the switching piston is increased by the oil pressure because the switching oil pressure within the intake rocker shaft is above the specified pressure, and so the wing of the high speed rocker arm reaches the switching piston. Accordingly, the intake valve is driven by the high speed rocker arm.