SOHC and DOHC refer to the valvetrain configuration in an engine. Here's a breakdown of the differences and the reasons for their use:
SOHC (Single Overhead Camshaft): In an SOHC engine, a single camshaft is positioned above the cylinder head, driven by the crankshaft via a timing chain or belt. The camshaft operates both the intake and exhaust valves of the engine. It uses rocker arms or other mechanisms to transfer the camshaft's motion to the valves.
DOHC (Dual Overhead Camshaft): In a DOHC engine, there are two camshafts positioned above the cylinder head. One camshaft is dedicated to operating the intake valves, while the other operates the exhaust valves. The camshafts are either driven by the crankshaft directly or through an intermediate shaft, and they actuate the valves directly without the need for rocker arms.
The primary advantage of DOHC engines over SOHC engines is their ability to provide precise control over valve timing and lift. Since each camshaft is dedicated to a specific set of valves, the timing and lift of the intake and exhaust valves can be optimized independently. This allows for better engine performance, higher rev limits, improved fuel efficiency, and potentially increased power output. DOHC engines also tend to have fewer moving parts than SOHC engines, reducing valvetrain mass and enabling higher engine speeds.
SOHC engines, on the other hand, are often simpler and more compact. They have a smaller number of components, which can result in lower manufacturing and maintenance costs. SOHC engines may be favored in applications where cost, weight, or packaging constraints are a concern, or when the specific requirements of the engine do not necessitate the added complexity of a DOHC setup.
Both SOHC and DOHC engines have their merits and are used in various motorcycles based on factors such as performance goals, cost considerations, engine size, and intended use. Manufacturers choose the valvetrain configuration that best suits the specific requirements of the motorcycle's design and target market.