What is the difference between single overhead camshaft and double overhead camshaft?

[LoganMarie]

A single overhead camshaft (SOHC) is arranged with one camshaft in a cylinder head, while a double overhead camshaft (DOHC) has two camshafts in a cylinder head. Both SOHC and DOHC designs allow the engine to operate at higher speeds. The main differences between them are as follows: 1. Driving method: The SOHC drives the intake and exhaust valves through rocker arms to achieve opening and closing, while the DOHC uses one camshaft to control the intake valves and another to control the exhaust valves. 2. Usage scenarios: Engines with SOHC are almost obsolete, typically found in older engines with outdated technology. DOHC is essential for multi-valve engines. If each cylinder has three to five valves, DOHC must be used. Most modern engines adopt DOHC design, with each cylinder having four valves—two intake and two exhaust. This design allows for more efficient air intake, more thorough exhaust, improved engine efficiency, and reduced fuel consumption. DOHC can also be paired with variable valve timing and variable valve lift systems for intake and exhaust, further enhancing engine efficiency and fuel economy. Therefore, most current engines use DOHC design.