Valvetronic: How does the variable valve lift system work?
Valvetronic is a designation for BMW engines equipped with a variable valve lift system. It is a system that, combined with variable valve timing, allows changing the position of the camshaft independently of the position of the crankshaft. It can also change the lift and length of time the valve is open.
This technology is used to optimize engine parameters. Thanks to the Valvetronic system, engines achieve higher performance, lower fuel consumption, and lower emissions.
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Some petrol engines from BMW are equipped with the Valvetronic system (variable valve lift), combined with the Double Vanos system and thus variable valve timing.
How Valvetronic works?
The Valvetronic system, in combination with the Double Vanos system, enables a fully variable valve lift, making it possible to replace the throttle valve. BMW engines equipped with the Valvetronic system only have a throttle valve for emergency mode.
The throttle valve is constantly open if the engine works as it should. By replacing the throttle valve, it was possible to eliminate the losses when air flowed through it. The Valvetronic system was introduced in 2001 in the BMW Compact 316ti model.
In a turbocharged engine, this system was used for the first time in the N55 engine, which was used, for example, in the BMW 535i (F10/F11/F07) or BMW 335i (E90/E91/E92/E93). The BMW car gradually began to equip its other engines with this system.
The main reason for using this system is the higher performance of the engine, its lower consumption, lower emissions, and a faster and better response to stepping on the gas pedal.
As I already mentioned, Valvetronic is a variable valve lift timing system, combined with the Double Vanos system, and therefore a variable valve timing system.
This system can change the position of the camshaft relative to the crankshaft by up to 60°, and thanks to the electromechanical device, it allows the stroke of the intake valves to be smoothly changed from the minimum stroke (0.3 mm) to the maximum stroke (9.7 mm).
Changing the setting between minimum and maximum valve lift takes just 300 milliseconds, the same time it takes to preset the Double Vanos variable valve timing system.
Construction of the Valvetronic system
The distribution mechanism of the Valvetronic system additionally contains an intermediate rocker, which, together with the regular rocker, forms the connection between the camshaft cam and the valve.
With the help of an eccentric shaft, the intermediate rocker thus affects the lift of the suction valves. The eccentric shaft, on which the intermediate rockers are located, moves with the help of an electric motor.
This method of controlling the valves is very demanding on production accuracy. All components of the valve train must be manufactured with great precision. That is why the intermediate and valve rocker arms are marked with the same serial number, which is laser-burned on the parts.