1.VANOS
BMW VANOS system is operated by a vehicle engine management system, a combination of hydraulic and mechanical cam control device. VANOS system is based on a adjusting mechanism capable of adjusting the relative position of the intake camshaft and crankshaft. Double VANOS adjustment mechanism to increase intake and exhaust camshaft.
VANOS system to operate an intake camshaft of the engine speed and accelerator pedal position. When the engine speed reaches a minimum, the intake valve will then open to improve the idle quality and smoothness. When the engine is in the medium speed, early intake valve opens to increase the torque and to allow exhaust gas recirculation in the combustion chamber to reduce the fuel consumption and exhaust emissions. Finally, when the engine speed is high, the intake valve opening is delayed again to play the greatest power.
VANOS system greatly enhanced emission management, increases output and torque, provide better idle quality and fuel economy. The latest version is double VANOS system VANOS, is used on the new M3 models. The technology was first used in 1992 on the BMW 5 Series models of the M50 engine.
In an overhead camshaft engine, the camshaft are connected by a belt or chain gear and the crankshaft. There are a number of chain and sprocket system in the BMW VANOS engine. The crankshaft sprocket drives the exhaust cam, the exhaust cam sprocket is bolted to the exhaust cam, the second set of gears driven through the second intake cam of chains, a large intake cam sprocket is not fixed the cam, because there is an intermediate macropores, spiral teeth have a bore in the outer end of the cam there is a helical gear, but it is too small to large chain wheel is connected to the inside of the gear. There is a small cup with a metal helical gear, which cooperates with the cam inside, with the outer sprocket. Variability VANOS system is derived from the helical gear. Control means acting on the cup-shaped receiving DME (digital electronic engine management system) the hydraulic drive means of hydraulic pressure mechanism.
When idling, the cam timing is retarded. In the non-idle state, DME solenoid is energized to push the cup-shaped gear control oil pressure, pushes the cam ahead of 12.5 degrees at medium speed, then 5000 rpm / min, allowing it to return to the initial position. When the operation speed, the better the larger thrust of the pneumatic cylinder, the greater the torque. We heard the noise is caused by a cup-shaped device due to tolerances and out sprocket slight swing sound.
under the action of the accelerator pedal position and engine speed, intake and exhaust camshaft valve timing were adjusted according to the required engine power system VANOS bis (bis variable camshaft control) thereby torque has been significantly improved.
In most single VANOS BMW engine system, the intake cam timing varies only in two distinct points of the number of revolutions. While the double VANOS system, constantly changing range of revolutions in most of the intake and exhaust cam timing.
double VANOS system increases the valve lift of 0.9 mm, so that the intake valve opening time and therefore delayed 12 degrees. A rapid and precise adjustment of the camshaft, bis VANOS hydraulic system requires very high to ensure that provide greater torque at low engine speeds, there is more power at high speeds. With the incomplete combustion gas is reduced, the engine idle speed is improved. Special engine management control system of the preheating phase will help the catalytic converter reaches its operating temperature faster.
bis VANOS power system improves low speed, so that the torque curve can be set to flatten and expand power band for the camshaft. Dual VANOS system of the engine torque peak is lower than 450 rpm VANOS single, high power peak 200 rev / min, the torque curve at 1500-3800 rev / min is also improved. Meanwhile, the torque down rate does not exceed the peak power.
double advantage VANOS system is characterized in that various operating states, the system can be independently controlled hot exhaust gases into the intake manifold. This is known as internal exhaust gas recirculation, so that the available components in the exhaust gas is recirculated.
In the engine warm-up process, the system improves the VANOS oil / gas mixture, and helps the catalytic converter is heated quickly to normal operating temperature. When the engine is idling, the system can be maintained smooth and consistent idle speed, thanks to the exhaust gas recirculation is reducedA minimum. Under partial load conditions, the exhaust gas recirculation to a higher level, the engine allowed to work in a larger opening angle of the butterfly valve in order to obtain better fuel economy. Under full load member, a lower recirculation system recovery capacity that each cylinder to provide as much oxygen.