Miller cycle engine is a supercharged four-stroke engine based on Otto cycle. It was first patented by Ralph Miller, an American mechanical engineer, in the1940s, but it was not until the1990s that Japanese Mazda applied it to its large RV series Millenia that this engine design began to be widely known in the world.
How does it work?
Generally speaking, the working principle of an Otto cycle engine is the basic four-stroke mode: intake (mixed fuel and air are injected into the cylinder through one or more intake valves), compression (mixed fuel and air are compressed), ignition (mixed fuel and air are ignited by a spark plug near the apex of the compression stroke) and exhaust (the combusted exhaust gas is discharged from the cylinder through one or more exhaust valves).
Because of its simple structure and low utilization rate of fuel and waste gas, it will be gradually eliminated by the market.
Miller cycle engine abandons the traditional complex connecting rod structure and replaces it with valve timing to create this effect. The solution is to delay closing the valve at the end of the intake stroke, which will "spit out" a part of the inhaled mixture, then close the valve and start the compression stroke.
Simply controlling the opening and closing timing of a valve will result in the effect that the expansion ratio is greater than the compression ratio, so compared with the traditional Otto cycle engine, the energy contained in the exhaust gas can be fully utilized again, which is one of the reasons why car companies like to use Miller cycle engine now.