Design and manufacturing techniques have been developed which make possible drastic reduction and precise control of poppet valve temperatures. For example, exhaust valves of revised design have operated 500 to 700F (280 to 390C) cooler than solid valves of conventional design.
Direct benefits of temperature reductions of this magnitude could lead not only to increased valve and associated component durability, but also to reduced or eliminated hot-spot ignition.
Valve cooling demonstrably provides better sealing of the combustion chamber during valve-closed events. Alloy cost in valves can be reduced, and metallurgical sophistication directed to the manufacturing process as well as to end use.
Whether cooler valves can result in smoother combustion or permit higher compression ratios with unleaded fuels cannot as yet be determined in contemporary cylinder heads. Modifications would be required to permit more uniform and adequate coolant velocity around some valve guides which currently cannot manage stem heat rejection from super-conductive valves.