VANOS

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VANOS (Variable Nockenwellen Steuerung) is an automobile variable valve timing technology developed by BMW in close collaboration with Continental Teves. VANOS varies the timing of the valves by moving the position of the camshafts in relation to the drive gear. This movement varies from 6 degrees of advanced to 6 degrees of retarded camshaft timing.

[edit] Single VANOS

VANOS is a combined hydraulic and mechanical camshaft control device managed by the car's DME engine management system. The VANOS system is based on a discrete adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds continuous adjustability to the intake and outlet camshafts.

VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds and moderate load, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, and exhaust emissions. At moderate speeds and light loading the camshaft is retarded reducing fuel consumption. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed.

VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy. The latest version of VANOS is double-VANOS, used in the new M3.

VANOS was first introduced in 1992 on the BMW M50tu engine used in the 5 Series. <http://www.bmwworld.com/technology/vanos.htm>

[edit] Double VANOS

Later BMW added "double" VANOS to its M52tu engine series of inline 6 engines, which changes the mechanism from fixed position operation to continuously variable, and add the same functionality to the exhaust camshaft, on a number of its cars. Double-VANOS (double-variable camshaft control) significantly improves torque and emissions since valve timing on both the intake and outlet camshafts are adjusted to the power required from the engine as a function of gas pedal position and engine speed. On most BMW engines that use a single VANOS, the timing of the intake cam is only changed at two distinct rpm points, while on the double-VANOS system, the timing of the intake and exhaust cams are continuously variable through a range of ~40 crankshaft degress for the intake, and 25 degress for the exhaust. The advantage of double-VANOS is that the system controls the flow of hot exhaust gases into the intake manifold individually for all operating conditions. This is referred to as "internal" exhaust gas re-circulation, allowing very fine dosage of the amount of exhaust gas recycled. <http://www.bmwworld.com/technology/vanos.htm>