In an internal combustion engine, the opening and closing of the valves are constantly controlled by the Camshaft.
A camshaft adjuster, on the other hand, enables variable valve control. The basis for this varies in engine parameters such as the speed and the current power.
Find out more here about camshaft adjustment, symptoms, consequences of defects in the camshaft adjuster, professional diagnosis, repair, and costs of a defect.
Camshaft adjusters are a modern way to increase performance and efficiency. A camshaft phaser is a technology to increase engine efficiency.
It eliminates the rigid relationship between the number of revolutions of the crankshaft and the control times of the valves. It can thus increase the engine’s performance and torque and optimize fuel consumption and exhaust gas values. The car manufacturers use very different principles for camshaft adjustment.
What is camshaft adjustment? Camshaft phasing is a method that allows the valve opening times of a four-stroke engine to be flexibly controlled. In this way, an increase in the efficiency of the motor is possible.
This increase can increase power and torque or reduce fuel consumption. The Camshaft is not changed, only its rotation angle or valve lift.
Therefore, camshaft adjustment is also called variable valve timing or variable camshaft timing. It is in contrast to the one-time setting of the control times, which takes place when the engine is assembled.
The crankshaft normally drives the Camshaft via a chain, gears, toothed belt, or vertical shaft.
The relation between the crankshaft’s and Camshaft’s revolutions is the same in all speed ranges in a classic four-stroke engine: the camshaft gear always has twice the number of teeth as the crankshaft gear, so that the Camshaft always rotates exactly half as fast as the crankshaft.
The valve opening times (the so-called control times) are therefore fixed and always the same at all engine speeds since they depend on the Camshaft’s revolutions.
A camshaft adjuster eliminates this rigid relationship between engine speed and control times and enables variable valve control depending on engine speed and load.
The secret of the camshaft adjuster lies in influencing the overlap times: In every four-stroke engine, the intake and exhaust valves are open simultaneously for a short time during each power stroke; this period is referred to as the overlap time.
Increasing the overlap time increases the engine’s performance at high speeds because more air enters the cylinder, increasing performance.
At low engine speeds, however, the torque drops due to a longer overlap time because exhaust gas is sucked back into the cylinder’s combustion chamber.
Therefore, a general extension of the overlap time does not make sense. A camshaft adjuster flexibly controls intake and exhaust times and thus the overlap time depending on engine speed and load.
There are various ways to adjust the Camshaft. In principle, a distinction is made between phase adjustment and valve lift adjustment:
The valves are opened earlier or later if necessary with a phase adjustment. The most common is the hydraulic phase, in which a swing motor phaser with engine oil pressure influences the valve opening times.
However, this hydraulic camshaft adjustment has certain limits in optimization, so most manufacturers today use electromechanical camshaft adjusters.
Alternatively, an increase in performance can also be achieved by changing the valve lift, which already achieves an increase in torque at low speeds and thus compensates for the disadvantage of the phase adjustment.