The SOHC (single overhead camshaft) engine is rarely used in the common high displacement performance models in the market, because the commonly used speed of motorcycles is high.

The structure of SOHC is simpler than that of DOHC, but although it only has one camshaft, it needs to be transmitted to four valves through two valve rocker arms to control the opening and closing of the valves.

advantage:

Due to the fact that there is only one camshaft, which is directly driven by the timing gear, the engine is less affected by the resistance of the camshaft’s rotation when the speed increases, and can complete the output of the low speed part more quickly. The maintenance cost is lower, the structure is simple, and fuel is more economical on commonly used low speed roads.

Disadvantages:

At high speeds, due to the inherent elasticity of the valve rocker arm, there are many reciprocating components that generate inertia. Therefore, the valve stroke control at high speeds may lack stability and accuracy, and there may also be some unnecessary vibration or noise.

DOHC

As the name implies, DOHC naturally drives two camshafts. Because it is two camshafts, the camshafts can rotate and press the valves directly. There is no medium of valve rocker arm, but it needs longer timing chains or belts to drive.

advantage:

Structurally speaking, the stability and accuracy of high rotation ventilation for the engine are better, which is conducive to maximizing the engine’s performance. Due to the absence of too many reciprocating accessories and transmission media, vibration control is better. The use of two independent cams allows for the use of a V-shaped combustion chamber, and the valve angle can also be more flexible in design. The spark plug can be placed in the center of the combustion chamber, making a certain contribution to fully uniform combustion.

Disadvantages:

Due to the need to drive two cams, there will be a loss of torque in the low-speed acceleration range of the engine. Due to its complex structure, maintenance and repair costs and difficulties are higher than those of SOHC.

In large displacement engines, most engines are using DOHC because the structure can better perform the driving quality of large displacement engines, and the single stroke power performance of large displacement engines is also strong, and the loss ratio for low torsion will be smaller.

Just like cars, if small household cars with very small displacement are equipped with DOHC, it is better to compress costs and improve cost-effectiveness than to use SOHC steadfastly to improve the user experience.

However, it should be emphasized that DOHC cars do not necessarily have poor low torque, and SOHC cars do not necessarily have strong low torque. It still depends on the tuning settings of other engine components. The two structures only affect the performance potential of the engine and the fuel economy and quality under certain operating conditions.