According to the official website, the Coates Spherical Rotary Valve System creates "a quieter engine with higher specific power output and longer life than conventional poppet valve engines due to better 'breathing' capability and higher speed capability." In fact, it's "the single most significant development in engine technology in the past thirty years." Not being the most mechanically-minded pistonhead on the planet, I asked Sajeev Mehta to check it out: "Its a logical extension of innovations like roller rockers: reduced friction, more power, efficiency etc. The general feel I got from people who know more than me: sealing a spherical valve isn't gonna work for a production car. Today's engines have to last over 100k miles without any trouble, and engine "blow by" will be even worse here… and don't even think about pressurizing these valves with a turbo/supercharger/ Good night! As for their claim of their valves not needing oil. Strap on an A/C compressor: sit in traffic in 100 degree weather on a heat-soaked hunk of tarmac and those valves will be begging for extra lubrication. The big red flag for me: their they compared it to a regular engine without an EGR valve. That's like challenging Carl Lewis to a 100m race and making him do it barefoot on hot asphalt. Everyone uses EGR valves for a good reason; they reduce NOx (the third row on their chart) emissions by something like 70% or more. "On the exhaust stroke the poppet exhaust valve stems allow "back" pressure through the valve guides into the engine casing. This pressure is then redirected through the fuel induction system and in turn is reburned in the engine creating yet more hydrocarbons, carbon dioxide and carbon monoxide." Except that happens on high mileage motors with worn valve guides/springs (valves snap shut plenty fine when new). It took 150k miles for my 5.0 Ford to get weaker/slower/dirtier from valvetrain age. Newer engines are even better at valvetrain durability for many reasons. I seriously question if the Coates engine will fare much better after that type of punishment. I'm skeptical, but would change my tune with better info. EPA-style tests that carmakers do wouldn't hurt."
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