fourvalve

Fourvalve is a term used in engineering to describe a system that uses four valves. In common usage, it refers to four valves per cylinder in internal combustion engines, where each cylinder contains two intake valves and two exhaust valves.

The four-valve-per-cylinder arrangement is typically implemented with a dual overhead camshaft (DOHC) setup, though other cam trains are possible. This configuration increases the total valve area available for air and exhaust to flow, improving volumetric efficiency and engine breathing, particularly at high RPM.

Benefits include higher potential power output, better throttle response, and reduced pump losses. The design supports higher compression ratios and more efficient combustion, as well as advanced valve timing strategies such as variable valve timing and lift control. The increased flow capacity can enable better peak performance without a drastic increase in displacement.

History and usage: The concept gained prominence in the 1980s and 1990s as manufacturers sought to improve performance without increasing engine size. It became common in both automobiles and motorcycles, with many performance-oriented production engines adopting four valves per cylinder.

Limitations: The four-valve design adds complexity, weight, and cost due to additional valves, springs, and actuators. Maintenance considerations include valve clearance, seat durability, and potential timing issues. Advances in materials and manufacturing have mitigated these drawbacks, contributing to the widespread adoption of four-valve engines in modern designs.

See also: multivalve engine, internal combustion engine, overhead camshaft.