BMW's VANOS - An Answer to Modern Variable Valve Timing

Vanos is a variable valve timing technology developed by BMW. This technology was first launched by BMW in 1992 and was used in the M50 engine(an inline 6-cylinder engine used by BMW from 1990–to 2000). This was a single vanos engine(I'll explain this term later).

Purpose of Vanos: Vanos helps control valve timing by using electrical, mechanical, and hydraulic systems. It uses various sensors like camshaft and crankshaft position sensors. It also uses an actuator which is called a vanos solenoid.

This system has helped in gaining control over the engine by controlling valve timing that’s why this system has helped in optimizing fuel efficiency, performance and power.

2 Basis Types of VANOS:

There are two basic types of vanos:

1. Single Vanos
2. Double Vanos

Single Vanos: Single Vanos only controls air intake by adjusting the intake camshaft to advance or retard timing. This technology was first used in 1992 in the BMW M50 engine, which can only adjust variable valve timing to 2 positions. But as the Vanos became more and more advanced, they introduced Single Infinitely Variable Vanos in 1998 in N62(V8 engine). Term infinitely variable means it can adjust valve timing to any position regarding engine load and speed.

Double Vanos: Double Vanos controls both intake and exhaust timing by adjusting the camshaft. This was first used in 1996 in S50(6-cylinder) engine. Double Vanos are better than single vanos in terms of fuel efficiency, performance, and power.

Working

VANOS system works on electrical, mechanical and hydraulic concepts. Vehicles DME(Digital Motor Electronics which controls engines) gets data from camshaft sensor about which condition(advance or retard) is good according to current conditions.

VANOS unit has teo ports one for cam retard and other for cam advance. When it has to retard timing Port C is open from solenoid and teeth of helical gear moved away or outside from cam gear which rotates camshaft and all valve events happen later.

To advance timing Port B is open from solenoid and teeth of helical gear are meshed inside cam gear and helical gear moves inside cam gear. This rotates camshaft such that timing is advance and valve events happen earlier. You can understand this mechanism by following diagram.

Vanos Solenoid

This solenoid has two ports for cam advance and retard. Oil enters from point A and is filtered to avoid any internal damage. After that it passes from point E to F and by the position of piston it flows from advance or retard port.

Remeber this solenoid has an electromagnetic mechanism that helps it in changing position and block advance or retard port. Excess of oil flows out from point D.

When Cam Advance is required?

Cam advance is helpful for high power output at lower rpms. Cam advance also provides more power and better fuel efficiency. By advancing cam valve timing is optimized more air fuel mixture enters the cylinder which in result provides better low-end torque and also improves responsiveness. This is really helpful in off-roading or towing of heavy loads. It provides better fuel economy by entering more air/fuel mixture and burning it properly by advancing spark at the same time.

When Cam Retard is required?

Cam retard reduces risks of detonation. Whenever there is a risk of engine knock cam retard is very helpful in that situation. It is also helful in reducing air/fuel mixture. It also applies less stress on different engine parts which is very good for engine's life and its reliability.

VANOS vs VVt-i

VANOS allows more adjustibility, much better and precise control over different speeds. It also optimizes power output and torque. But VVT-i(a variable valve timing mechanism used by Toyota/Lexus) provides less adjustments. VVt-i is better than VANOS in terms of reliability.

Conclusion: BMW Vanos was developed to reduce emissions, improving fuel efficiency and performance. This system works in conjunction with valvetronic, which can be understood by reading the previous article. VANOS is better than other technologies as it provides more range of control and better performance.