Fourvalvepercylinder

Four-valve-per-cylinder is an internal combustion engine configuration in which each cylinder contains four valves. The typical arrangement is two intake valves and two exhaust valves per cylinder, though valve sizes and exact layout can vary. This design aims to improve the flow of air and exhaust gases, enabling more efficient combustion and higher engine speeds.

Most four-valve heads use dual overhead camshafts to operate the four valves per cylinder, along with timing systems such as variable valve timing and lift. The additional valves allow more complete filling of the cylinder at high rpm and more efficient exhaust scavenging, which can support higher compression ratios and better overall performance without a large increase in engine size.

Advantages of the four-valve-per-cylinder design include improved volumetric efficiency, better breathability at high engine speeds, greater potential for power and torque across a wider rpm range, smoother throttle response, and potential gains in fuel efficiency. Drawbacks include greater mechanical complexity, higher manufacturing and maintenance costs, and increased weight of the cylinder head compared with simpler valve configurations.

History and adoption: the concept of multi-valve heads emerged in the mid-20th century and became widely adopted in production engines during the late 20th century. Four valves per cylinder became common in many modern automotive engines, particularly in performance and efficiency-focused designs, as manufacturing techniques and materials allowed lighter, more precise valvetrains.

Applications are broad, spanning passenger cars, motorcycles, and some marine engines, where the balance of power, efficiency, and emissions benefits justifies the added complexity.