|Production Years:||1928-1929||Country:||United States|
One particularly unconventional engine came from America. This four-stroke engine had sleeve valves and was dubbed "The Silent Knight" after its inventor, Charles Yale Knight. In the Silent Knight there are ports, as in a normal two-stroke engine, but they are located at the top of the cylinders. Two sleeves, internal to the cylinders, slide up and down to open and close these ports. The sleeves are connected to a small crankshaft synchronized with the main crankshaft. This system is called "desmodromic" as there are no springs and every motion is "positive". The desmodromic system’s main advantages are silence and reliability. During the first part of the 20th century, valves were noisy and fragile.
In 1927, the Willys-Overland range cars was expanded by the arrival of the Type 56, a comfortable sedan whose six-cylinder Silent Knight engine had a "rectifier". This important new feature was introduced to combat the sleeve-valve’s reputation for using too much oil. Cars with Silent Knight engines always trailed a cloud of blue smoke. The solution to this problem involved forcing excess oil through holes in the cylinder wall near the exhaust port. The oil mixed with gasoline was fed to the rectifier, where the mixture was distilled in a chamber heated by exhaust gas. This process enabled oil to be returned to the crankcase while gasoline fumes went out through the exhaust pipe. Although clever and effective, the rectifier was not fitted to engines used in Europe.