Chrysler HEMI V8 MDS & VCT Systems

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Chrysler HEMI V8 MDS & VCT Systems

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Chrysler HEMI V8 MDS & VCT Systems
http://mdhmotors.com/chrysler-hemi-v-8-mds-vct-systems/
This article will explain the Chrysler MDS and VCT system operation and components used on the new HEMI 5.7L V8. Multiple Displacement Systems (MDS) is a system used on the 5.7L Chrysler HEMI V8 engines to allow 4 cylinder operation during light loads conditions. The timing of the opening and closing of the valves is controlled by the Variable Cam Timing (VCT) system.

Chrysler HEMI VCT

The PC2M varies the timing of the valves, advancing or retarding their opening relative to piston motion. The 5.7L HEMI has one Oil Control Valve (OCV), an electro hydraulic pulse width modulated solenoid that controls oil pressure to the camshaft phaser by taking supply oil and routing it to two oil passages inside the OCV. The OCV is mounted horizontally and centered behind the timing cover. The OCV is attached to the block. The OCV connector is part of the MDS harness. The camshaft phaser replaces the standard camshaft sprocket. The phaser is attached to the camshaft by a single bolt. The phaser has internal vanes. The OCV regulates oil flow to either side of the vanes to cause the phaser to rotate and thus change the position of the camshaft. One oil gallery supplies oil to the OCV, and two oil galleries supply oil to the number one camshaft bearing for advance and retard of the camshaft phaser. There is a tone wheel attached to the camshaft phaser that is used by the camshaft position sensor. The OCV controls oil flow to the camshaft phaser, thereby controlling the operation of the VCT system.

On the Chrysler VCT system the valve timing is advanced in default position so the below OCV values will work as follows:

* If the OCV is 0% the valve timing is advanced in the default position.
* If the OCV is at 100%, the valve timing is retarded.
* If the OCV is at 50%, there is no oil flow and the system holds its current position.

Chrysler HEMI MDS

Multiple Displacement System (MDS) is a system used on the 5.7L Chrysler HEMI V8 engines to allow 4 cylinder operation during light load conditions. MDS was introduced in the 2005 on the 300C and Jeep Grand Cherokee platforms. MDS was also released on the Durango and Ram Pickup truck in 2006. 5.7 HEMI has V8 or V4 mode there are 4 solenoids and special lifters to allow for cylinder kill during light load conditions. The MDS Oil Control Valve is a single solenoid used for each deactivation cylinder. It is a Three port, two position spool valve driven by a solenoid and has a oil pressure range for MDS control at around 18-75 PSI.

The new Chrysler engines utilize MultiAir, a variable valve timing and lift technology which allows for separate timing of each cylinder. The system uses electro-hydraulic valve actuators; a solenoid, energized with each rotation of the camshaft and regulates the amount of oil sent to the actuator, which controls the amount of lift, from completely closed to completely open. The valves can also vary the timing. This system appears to be more effective than normal variable valve timing. Unlike fixed lobes on a conventional camshaft that control valve lift and duration, the intake valves with the MultiAir system are electro hydraulically controlled. This results in wide flexibility of intake valve openings for better fuel economy and power with lower emissions.
This was pretty cool information. Visit the site to see the associated pictures and diagrams.
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