The Function of VANOS in BMWs
BMWs have some features and options that are not available on all makes and models, one of which is VANOS or variable valve timing. VANOS uses a combination of mechanical and hydraulic camshaft control mechanisms, which is managed by the vehicle’s DME engine management system. The VANOS system can adjust the intake camshaft position.
The History of VANOS
In older cars, it was easy to manually tune an engine through timing adjustments. In those vehicles, the crankshaft drove the timing chain which then spun the gears located in the head and turned the engine cams.
It became popular to put in a different kind of cam to improve a vehicle’s performance. You had to decide if you would rather have low-end torque for cruising or high-end power for racing and performance. The vehicle’s engine functional performance and timing were set in stone. However, advanced technology allowed timing to be changed more easily. Many auto makers created designs that allow variable valve timing, also known as VVT, but they all offered different answers for a single question.
How can the best power curve be achieved on a non-turbo engine while reducing fuel consumption and emissions?
The capability to adjust an engine’s timing while in operation is a wonderful invention that enables great engine performance cruising in a low RPM, but also has the capability to spike the RPM. BMW’s VANOS stands for Variable Nockenwellen Steuerung.
The VANOS is incorporated in the BMW M50 engines, where they focus on controlling the cam gear, which has a mechanical link to the exhaust gear by a chain. VANOS was designed with the cam and the cam gear each being independent, and each of them being made with their own splines. The gear of the VANOS has two separate sets of splines, with the outer set working for the cam gear and the inner set working just for the cam. A helical gear, which is a twist, works with the gear inserting deeper between the car’s cam gear and the cam, the position changes sometimes only slightly.
How VANOS Works
When the car’s engine is idle, the gear retracts. As the RPM increases, the cup will insert deeper into the gear and adjusts the timing of the intake valve. This leads to overlap between the intake and exhaust, letting the gas from the exhaust recirculate to improve emissions while the vehicle is cruising. When the car accelerates into higher RPM ranges, the solenoid will close and the cup will retract, which reduces overlap and focuses on maximum power.
Because the solenoid gets used so often, it often fails from wear and tear. Newer BMW models feature a hydraulic pod, which extends into both cam gears, controlling both the intake and the exhaust cam timing. The newer system is an improved version of the original VANOS, allowing continuous timing changes. The ECU can change the timing of the intake and exhaust cam as it sees fit. The ECU can also use different maps created to meet the needs of different driving situations.
The VANOS system performs some amazing work, but it is yet simple in design. Many of the best automakers have come up with a form of variable valve timing, but BMW was one of the few automakers to take full advantage of this state-of-the-art feature early on.
Addressing VANOS Problems
If your BMW’s VANOS is not operating up to par, or if the solenoid needs to be replaced, take your car to a qualified BMW automotive technician. Our German master technicians at Stress-Free Auto Care, can make sure your BMW is up to speed.
