Cam Phaser
An adjustable camshaft sprocket that rotates relative to the camshaft to adjust valve timing on the fly.
A cam phaser is a key mechanical component of Variable Valve Timing (VVT) systems, mounted on the end of the camshaft. Unlike traditional fixed timing gears, a cam phaser is an adjustable sprocket that can rotate the camshaft relative to the timing chain or belt. This rotation advances or retards the camshaft timing on the fly.
Most modern cam phasers are hydraulically operated, utilizing pressurized engine oil regulated by a solenoid (VVT solenoid) to change the timing angle. By adjusting when the intake and exhaust valves open and close relative to the piston position, the Engine Control Unit (ECU) can optimize engine performance, fuel efficiency, and emissions across the entire RPM range.
If the cam phaser fails or if the engine suffers from low oil pressure or oil starvation, the phaser may not lock or rotate properly. This causes a distinct ticking or knocking sound (often referred to as 'phaser knock'), a check engine light, and decreased engine performance.