Quote:
Originally posted by Hudson
As far as not needing oil in the head, are you sure about his? I don't care how "low friction" the parts are, those cams are moving quite fast and will be rubbing against other parts (or else there would be no seal and no compression) which will cause friction. Oil will be necessary in the head. Teflon on teflon (the lowest friction combination possible) would still need lubrication at 2,500 rpm.
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Quote:
Originally posted by http://www.coatesengine.com/Body.htm
Absence of poppet valves and other operating accessories normally housed under the valve cover has permitted elimination of both oil lubrication and cooling water flow in the upper portion of the cylinder head. This reduces the overall engine height by as much as 20 cm from that of its conventional counter part, and maintains a clean engine.
The new, patented simple valve-train unit has minimized the area of contact for fluid flow through the gas exchange ports by making use of wide-open circular cross-sections. This significantly cuts down the pumping loss and unmatchably increases the volumetric efficiency to achieve a high torque/power-density engine.
The new dynamically balanced rotating spherical port valve eliminates entirely mechanical noise produced by current poppet-valve components. Hissing sound generated as gas flow squeaks through the narrow annulus valve opening in the conventional cylinder head is no longer audible. At the same time, the new unit cuts down, by an order of magnitude, the need for power out of the crankshaft. Normally a big parasitic power drain is required in conventional engines to drive the valve train.
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Without quoting the entire web site, poke around, and they have some info on the materials used to lubricate the valves. In fact, I think they even went so far as to say that their heads coul operate without needing a valve cover in place!
As for the 10 to 20 years ago thing, I think you're only half right. Valves themselves still represent disruptions in airflow as the air/fuel mixture enters the combustion chamber. This disruption can be used to help aid air/fuel mixing, but in general, I like the idea of eliminating valves altogether. Besides that, do you think that eliminating the cams will be sufficient to prevent valve float at high rpm use? I think that this will continue to represent a challenge for engine designers married to poppet valves.