bmw vanos engine
BMW VANOS, introduced in 1992, is a system that varies the intake camshaft timing in order to improve performance, fuel economy, and emissions. At idle, the camshaft is set to open the intake valves later, increasing idle quality and smoothness. As the engine speed increases through the middle part of the RPM range, the camshaft opens the valves earlier, resulting in more torque, better fuel economy, and reduced emissions. At high engine speeds, the camshaft is again set so that the valves open later to allow full power delivery.
BMW Double-VANOS was introduced in 1997 and adds the ability for the system to continuously control not only the intake camshaft timing but also the exhaust camshaft timing. This continuous adjustment by the Digital Motor Electronics (DME) results in higher torque at low RPMs, more horsepower at high RPMs, and reduced fuel economy and emissions.