Camshaft Adjustment Control Valves

Technical Bulletin: Camshaft Adjustment Control Valves

The camshaft adjustment valve (also known as an oil control valve) is an integral part of the variable valve timing (VVT) system in modern engines. Each manufacturer has different technology and terminology for the system, some of the most recognisable names include VVT, VVTi, VTEC and VTi (For a full list please see Table 1). 

There will also be some differences between manufacturers as to how the systems operate but fundamentally the concept remains the same…

So what is variable valve timing?

To understand how camshaft adjustment valves operate it is important to first understand the concept of variable valve timing.

In simplest terms, variable valve timing or camshaft adjustment advances or retards the opening times of valves in the engine to adapt to a range of operating conditions and desired results. As a result the operating efficiency of intake and exhaust valves  is greatly increased which in turn results in:

  • Reduced fuel consumption
  • Increased torque at lower engine speed
  • Improved horsepower at higher engine speeds
  • Internal exhaust gas recirculation
  • Reduced harmful exhaust emissions

How do camshaft adjustment valves work?

Generally variable valve timing is controlled by oil pressure. The engine’s ECU/PCM uses a host of sensors including the camshaft sensor and mass airflow sensor to calculate the required valve timing based on the current driving conditions. This is communicated as a pulse width signal to the camshaft adjustment valve which then controls the flow of oil. The valve is able to direct the flow of oil to the VVT hub by using an integrated solenoid and spool valve to advance or retard valve timing.

So what is variable valve timing?

To understand how camshaft adjustment valves operate it is important to first understand the concept of variable valve timing.

In simplest terms, variable valve timing or camshaft adjustment advances or retards the opening times of valves in the engine to adapt to a range of operating conditions and desired results. As a result the operating efficiency of intake and exhaust valves  is greatly increased which in turn results in:

  • Reduced fuel consumption
  • Increased torque at lower engine speed
  • Improved horsepower at higher engine speeds
  • Internal exhaust gas recirculation
  • Reduced harmful exhaust emissions

How do camshaft adjustment valves work?

Generally variable valve timing is controlled by oil pressure. The engine’s ECU/PCM uses a host of sensors including the camshaft sensor and mass airflow sensor to calculate the required valve timing based on the current driving conditions. This is communicated as a pulse width signal to the camshaft adjustment valve which then controls the flow of oil. The valve is able to direct the flow of oil to the VVT hub by using an integrated solenoid and spool valve to advance or retard valve timing.