Working of a DOHC engine
DOHC means Double OverHead Cam, or sometimes it could be called "Twin Cam" or "Double Cam." Most modern cars have DOHC engines.
A typical DOHC engine has two camshafts and 4 valves per cylinder. One camshaft operates intake valves that are installed on one side, while another camshaft controls exhaust valves on the opposite side. With this design, camshafts can be installed further apart from each other. This allows the intake valves to be at a larger angle from the exhaust valves, which results in a more direct air flow through the engine with less obstruction. In other words, a DOHC engine can "breathe" better and thus produces more horsepower out of smaller engine volume.
Technologies like Direct Injection, Variable Valve Timing and Variable Valve Lift can be easily implemented in a DOHC engine, further improving fuel efficiency.
Downsides of the DOHC technology include a more complex design with additional timing belt or chain components. A timing belt needs to be replaced at recommended intervals, adding to maintenance costs.