Valvetrain is the term that collates all the mechanisms and parts that control the operation of the valves. Valves are devices responsible for halting and controlling the flow of a liquid, gas and other materials through a passage, pipe, inlet and outlet and so on. It consists of valves, rockers arms, pushrods, lifters and camshafts. Valvetrains are built in several configuration. It has different layouts but still performs effectively. Car enthusiasts and experts say that there is a level of effectiveness between each layout, one is better than the other. These layouts are distinguished through the location of the camshaft within the engine.
There are two overhead camshaft layouts, Single Overhead Camshaft (SOHC) and Double Overhead Camshaft (DOHC). These two camshaft layouts are two different ways to configure the valve train. This analysis will help you get to know more about the difference between SOHC and DOHC.
Before DOHC came, SOHC is already here, relatively known as Overhead Camshaft. SOHC engine is installed in the cylinder head and valves are being operated by the rocker arms or by directly using the lifters. Its design has less reciprocating mass than a comparable pushrod design, which allows a higher engine speed. If that happens, there will be an increase on power output for a given torque. With SOHC, valves are operated by the camshaft, which makes it easy to get the perfect timing at high rpm. With SOHC, the valvetrain is lighter, which is advisable for any engines or cars. The valve opens at an interval of 25 times a second at 3000 rpm. It also makes it possible to install three to four valves for every cylinder. One notable disadvantage of a Single Overhead Camshaft is that it requires a timing belt or chain with related components. It is more complex and has a more expensive design. Toyota and Volkswagen are manufacturers that used a directly actuated, SOHC parallel valve configuration with two valves for each cylinder.
DOHC or Double Overhead Camshaft is maybe the new trend in today's cars. The arrangement of this is that we use two camshafts in each cylinder. With DOHC, it is now possible to install multiple valves per cylinder and place intake valves on the opposite side from exhaust valves. The engine can give off a higher performance because it can breath better. It can now produce more horsepower with smaller engine volume. DOHC also makes it easier to to implement valve timing technologies where in you could tweak it far better through adjustable cam pulleys. One disadvantage of a DOHC is that it has a more expensive design. And another disadvantage of this setup is that it has more weight, more complexity and and higher cost. Additional weight is burden for the engine, that is why some car owners do not prefer this.
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