Variable valve timing system

The variable valve timing system continuously modifies the phases of the variable valve timing actuator and intake camshaft under the action of hydraulic pressure controlled by the oil control valve (OCV) so that the opening and closing phases of the valves are optimally matched to the operating conditions of the engine. Oil Control Valve Operation (OCV) based on signals from the camshaft position sensor according to engine operating conditions. It controls the hydraulic pressure acting on the variable valve timing actuator.

Work according to driving conditions: idling, light loads

By reducing the overlap, less combustion products are returned to the cylinder. This stabilizes the idling speed, improving fuel economy, and also guarantees the stability of the engine at light loads.

Medium loads

The overlap increases and the EGR ratio in the cylinder increases. This reduces friction losses (pumping losses), the combustion temperature decreases and the amount of CO in the exhaust gases decreases. The amount of hydrocarbon emissions is also reduced due to the re-burning of the non-ignited gas.

Heavy load, low and medium speeds

The intake valves close early, resulting in high volumetric efficiency while improving torque in the low to medium speed range.

Heavy load, high speed range

Intake valves close later, high volumetric efficiency ensures maximum power.

At low temperature

The overlap is minimized to prevent combustion products from entering the cylinders and to reduce the amount of additional fuel injected into the cylinders. This improves fuel economy and stabilizes high idle speeds.

When starting or stopping the engine

Starting performance is improved due to reduced overlap, as combustion products are not returned to the cylinder.

Table 2.12. Elements and their functions