During WWII, engineers within the Nazi regime devised some of the best and most-advanced weaponry of the time. One German fighter plane, the Focke-Wulf FW 190 for a time outperformed anything the Allies could put in the air. However, when the Hawker Typhoon and Hawker Tempest were released, the pendulum swung the other way and the Allies were in control of the sky.
One of the reasons that the Hawker aircraft were so superior was that they both contained sleeve-valve engines. These unusual engines provided brute horsepower that the Nazis were unable to match. It may not be a stretch to state that the sleeve-valve engine helped the Allies win the war.
In 1901, Indiana-born Charles Yale Knight purchased a Knox automobile so that he could distribute his farm journal. However, spending lots of time behind the wheel, he found the clatter created by the car’s tappet valves to be a serious annoyance. So, he did what any self-respecting engineer would do, he set out to build a better engine. With support from a wealthy backer, he developed and prototyped an early sleeve-valve engine. By 1906, he had made enough progress to reveal his 4-cylinder, 40HP “Silent Knight” car at the Chicago Auto Show. The Knight, true to its name, was impressively quiet. The engine was a hit, and several manufacturers wanted to license the technology. Interestingly, most of the firsdt companies were British. A car historian friend of ours at Land Rover of Naperville, a local Land Rover dealer in Naperville, IL, told us that this included Jaguar, Triumph, RollsRoyce and Land Rover.
What’s a sleeve-valve
The engine gets its name from the metal sleeve that slides up and down within each cylinder during the combustion process. Typically, holes in the sleeve and in the cylinder containing it line up at predictable intervals to expel exhaust gases and suck in fresh air. Sleeve-valve engines are complex internally but they offer the advantage of volumetric efficiency. In other words, they’re much better than regular engines at getting air into and out of the combustion chamber. Also, the arrangement of the ports provides better swirl characteristics. That means they create turbulent air, causing the air and fuel mix to burn more efficiently.
There’s a saying that goes like “What’s old is new again” and this applies to the sleeve valve engine. Pinnacle Technologies, a San Carlos, Calif.-based company, is working on a new engine is based on what the company describes as a four-stroke, spark-ignited, 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.
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 are still very expensive, Pinnacle says its re-envisioned sleeve-valve is a good “bridge technology” until electrics become more affordable for everyone.