How The Basic Position Works In the basic position, the exhaust camshaft is positioned so that the valves close shortly before TDC. The exhaust camshaft timing adjustment valve 1 (N318) is not actuated by the engine control unit. In this position, the oil gallery for timing retardation is open. Through oil galleries, oil pressure reaches the ring channel of the exhaust camshaft. From there, it travels through the frontal drillings in the camshaft to the oil chamber of the camshaft adjuster. From there it presses against the flutes of the inner rotor. The flutes turn to stop, turning the camshaft along with it. The camshaft remains in this position as long as the solenoid is not actuated. Idle The exhaust camshaft is set to the position from idle to engine speeds to “advanced” about 1,200 rpm. How The Idle Position Works The exhaust camshaft timing adjustment valve 1 (N318) is actuated by the engine control unit. This pushes the control piston and opens another oil gallery in the control housing. The engine oil now flows into the other ring channel in the camshaft and through the drilled camshaft into the camshaft adjuster. There it presses against the flutes of the inner rotor. The flutes are pressed in the direction of engine rotation, taking the camshaft with them, so that the exhaust valves open and close earlier. The oil from the chamber in front of the flutes runs through the drilling in the camshaft adjuster, the pocket hole of the securing bolt and the ring channel of the camshaft back to the solenoid valve. In the solenoid valve it flows through the oil return in the control box cover. Oil System The following pages introduce the oil system. The variable valve timing system operates at an oil pressure of 0.7 bar and above. Course of oil under pressure Oil pressure created by the oil pump flows through the cylinder block to the cylinder head and from there through an oil strainer into the control housing of the camshaft adjuster. Through galleries in the control housing, it reaches the ring channel in the camshaft and from there it travels through frontal drillings in the camshaft into the camshaft adjuster.
How The Basic Position Works In the basic position, the exhaust camshaft is positioned so that the valves close shortly before TDC. The exhaust camshaft timing adjustment valve 1 (N318) is not actuated by the engine control unit. In this position, the oil gallery for timing retardation is open. Through oil galleries, oil pressure reaches the ring channel of the exhaust camshaft. From there, it travels through the frontal drillings in the camshaft to the oil chamber of the camshaft adjuster. From there it presses against the flutes of the inner rotor. The flutes turn to stop, turning the camshaft along with it. The camshaft remains in this position as long as the solenoid is not actuated. Idle The exhaust camshaft is set to the “advanced” position from idle to engine speeds to about 1,200 rpm. How The Idle Position Works The exhaust camshaft timing adjustment valve 1 (N318) is actuated by the engine control unit. This pushes the control piston and opens another oil gallery in the control housing. The engine oil now flows into the other ring channel in the camshaft and through the drilled camshaft into the camshaft adjuster. There it presses against the flutes of the inner rotor. The flutes are pressed in the direction of engine rotation, taking the camshaft with them, so that the exhaust valves open and close earlier. The oil from the chamber in front of the flutes runs through the drilling in the camshaft adjuster, the pocket hole of the securing bolt and the ring channel of the camshaft back to the solenoid valve. In the solenoid valve it flows through the oil return in the control box cover. Oil System The following pages introduce the oil system. The variable valve timing system operates at an oil pressure of 0.7 bar and above. Course of oil under pressure Oil pressure created by the oil pump flows through the cylinder block to the cylinder head and from there through an oil strainer into the control housing of the camshaft adjuster. Through galleries in the control housing, it reaches the ring channel in the camshaft and from there it travels through frontal drillings in the camshaft into the camshaft adjuster.
253257008-VVT-variable-Valve-Timing.docx