|
 |
|
|
|
|
Latest News Variable Camshaft Actuators (VCA) Oil control Valves What a Technician needs to know when working on or diagnosing faults on a Variable Valve Timing (VVT) system. Brief description of VVT system. The variable valve timing system is now commonly fitted by most vehicle manufacturers to advance and retard the camshaft in relation to the crankshaft position within the cylinder. Early VVT systems were utilised to increase engine performance. A typical advanced system is the Toyota VVTL-i with continuous cam-phasing VVT and 2 stage variable valve lift plus valve opening duration applied to both intake and exhaust valves. A typical simple VVT valve cycle. The BMW (VVT) Vanos system (Variable Nockenwellen Steuerung) at lower engine speeds, opens the valves later during the intake stroke. This increases the vacuum and scavenging effect which improves idle quality and acceleration from a stationary condition. As the engine RPM increases, the valves are opened earlier to enhance Torque.
How does the VVT actuator oil control valve affect the VVT system? The VVT system generally utilises oil pressure as the internal force for the actuator to change the Camshaft phasing. The flow control of the oil pressure is performed by the VVT actuator control valve that is operated by a pulse width modulated signal from the PCM. The control valve integrates a solenoid and spool valve that allows engine oil to be directed to various paths. A typical VVT hydraulic circuit schematic.
Typical VVT faults and causes that affect its operation. Being a mechanical/hydraulic system that is controlled by electronics, there are a few areas of concern if the system is not maintained correctly.
Note: It is important to investigate any Service Information Bulletins that relate to the VVT system when a malfunction in the system occurs. A malfunction in the VVT system may cause the “Service Engine Soon” (MIL) light to illuminate and multiple fault codes logged in conjunction with loss of engine power and possible rattling sounds. Oil service schedules need to be adhered to as delaying service intervals is a main factor for VVT failure due to oil contamination and mechanical wear. Testing the Oil Control Valve. If the oil control valve is suspected of being faulty, checking the electrical resistance of the coil windings is a simple task.
If the resistance is within specs, the movement of the spool valve may be inhibited by internal foreign objects. Movement of the spool valve may be checked by powering the 2 terminals of the unit and it is recommended to renew the valve if it is suspect. On car testing of the VVT. Typical VVT vehicle system identification.
The Premier Auto Trade Emission range includes more than 45 Variable Camshaft Actuators (VCA), covering over 4.1 million vehicle applications in Australia and NZ. When you supply and fit products from Premier Auto Trade you can expect a product designed and tested to the vehicle manufacturer’s specifications offering OE form, fit and function. Premier Auto Trade distributes products throughout Australia via a network of specialised resellers and leading automotive groups.
|
Latest News
Tech Tips - Wheel Speed Sensors (WSS) |
|
| privacy statement terms of use terms and conditions sitemap news |  |
|