Presented at the Fall 2012 ICAIA Conference, Joliet Junior College, Joliet, IL.


Variable camshaft timing (VCT) and variable valve timing (VVT) have become common strategies used by many automotive manufacturers to increase engine performance, reduce emissions, and improve economy and driveability. This presentation was conducted at the fall 2012 ICAIA conference in Joliet, IL on October 5th, 2012. The two most popular methods include the use of a phaser to alter camshaft position and the use of multiple camshaft lobes with rocker arm coupling and de-coupling (both phaser and lobe switching methods can also be combined). VCT/VVT use can be employed on pushrod engines, DOHC, SOHC engines and can be utilized on just intake valves, just exhaust valves or both intake and exhaust valves. A review of mechanical components, hydraulic controls, and electrical controls is provided along with observations regarding operation. In addition, basic diagnostic trouble codes (DTC's) and troubleshooting points are discussed.