Camshaft Phasers

DESCRIPTION: 

Courtesy of CHRYSLER GROUP, LLC

Courtesy of CHRYSLER GROUP, LLC

The engine is equipped with Variable Valve Timing (VVT). This system adjusts the timing of all four camshafts independently using solenoids and oil control valves to direct oil pressure into the camshaft phaser assemblies. The four phasers are located on the front of the camshafts, behind the VVT solenoids, inside of the engine timing cover.

• The camshaft phaser assembly advances and/or retards camshaft timing to improve engine performance, mid-range torque, idle quality, fuel economy, and reduce emissions.
• The exhaust phasers are identified with EXH and the intake phasers are identified with INT.
• The exhaust phaser has a clockspring, the intake phaser does not.
• The camshaft sprockets are integrated with the camshaft phaser and are serviced as an assembly. Do not attempt to disassemble the phasers, they are not serviceable.
• Phasers are interchangeable between the right and left cylinder heads, but should be installed in the same location as removed.

Courtesy of CHRYSLER GROUP, LLC

The engine has an Oil Control Valve (OCV) for each phaser. The OCV also acts as a bolt for mounting the Phaser to the camshaft. The OCV spool valves are spring loaded and should move freely within the OCV body.

OPERATION: 

Courtesy of CHRYSLER GROUP, LLC

Each phaser position is adjusted using regulated oil pressure through the Oil Control Valve (OCV). To begin phaser movement, a voltage signal is applied to the Variable Valve Timing (VVT) solenoid to extend or retract the solenoid pintle. The pintle pushes against an internal spool valve within the OCV moving the valve forward and backward to direct oil flow.

Courtesy of CHRYSLER GROUP, LLC

At engine startup, system oil pressure overcomes spring pressure and unlocks the phaser lock-pin in preparation for phasing. The phasers remain in this position until a Powertrain Control Module (PCM) signal is given to pulse-width modulate the VVT solenoid. At engine shutdown, as oil pressure is reduced, both Phasers return to their lock-pin position.

Because the exhaust Phaser needs to travel to a position above and beyond the standard camshaft clockwise rotation, the assistance of a clock spring is required. The intake Phaser on the other hand, simply relies on the torsional resistance from the valvetrain to push it back towards lock-pin position.

Courtesy of CHRYSLER GROUP, LLC

The position of the spool valve inside the OCV determines which ports and chambers inside the phaser are being fed, either to advance, hold or retard the timing of the phaser sprocket relative to the camshaft. The spool valve also returns oil from the chambers to the sump. The Camshaft Position (CMP) sensor monitors the position of the camshaft with respect to the crankshaft and provides feedback to the PCM. As oil pressure pushes against the vanes of the phaser rotor, the rotor begins to move. Since this rotor is physically attached to the camshaft, rotor rotation causes the camshaft position to rotate relative to the standard sprocket position.