So, was the sleeve-valve engine an evolutionary dead end, as far as the advance of internal combustion?
Let's put it this way. Just like Hollywood likes to recycle old concepts and put a fresh spin on them when it's running low on new ideas, so does the auto industry. Electric cars, you may recall, were a big deal before (ironically) the electric starter made internal combustion cars highly practical. Electrics pretty much vanished from mainstream motoring until environmental concerns brought them back from the grave near the turn of the century.
And so, similarly, could the case be unfolding with the slumbering sleeve-valve engine. As the saying goes, "what's old is new again."
San Carlos, Calif.-based Pinnacle Technologies is counting on pent-up demand for clean, cheap transportation in Asia to snap up its modern interpretation of the sleeve valve. A new engine is based on what the company describes as a four-stroke, spark-ignited (SI), opposed-piston, sleeve-valve architecture.
Pinnacle founder Monty Cleeves says his patented engine can yield a 30- to 50-percent efficiency improvement over current internal combustion engines [source: Pinnacle Engines].
"This engine technology provides the fuel economy and CO2 emissions of a hybrid at a price that the whole world can afford," Cleeves said in a company-issued statement
Pinnacle says it isn't worried about electric vehicles making its technology obsolete any time soon. Instead, it believes there's a big opportunity to serve rapidly growing markets such as India and China. They and other developing countries want to curb greenhouse gas emissions while improving their citizens' standard of living, through motor vehicle ownership. Since electric vehicles and hybrids still carry a significant price premium, Pinnacle says its re-envisioned sleeve-valve is a good "bridge technology" until electrics become more affordable for everyone.
Pinnacle, which has received several million dollars in venture capital, said it was pursuing a licensing agreement with an Asian auto manufacturer and it expected production to begin in 2013.
Author's Note: How Sleeve-valve Engines Work
As a big military aircraft geek, I had heard of sleeve-valve engines prior to this assignment. But that was about the extent of it. Given their footnote-in-history status, I had always thought of them merely in the abstract. Unlike a poppet valve engine that you can study in your own driveway, these "sleeve-valve things" were to me just a forgotten, if quaint, technology, like steam locomotives. So when I tapped the power of the Interwebs to see them in action, I was instantly struck with both awe and admiration. How did folks 100 years ago figure out all the necessary angles, tolerances, weight balances and more to bring these incredibly complex machines to life? The fact that entrepreneurs today are looking to breathe new life into the concept speaks volumes about those original pioneers' genius and vision. One could argue that the original, twentieth-century sleeve-valve engines were "over-engineered" -- that is, they were too complicated for their own good. Or it could simply be that, lacking the advances in materials science and the precision of computer-aided design that we enjoy today, they were merely ahead of their time.
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