Atkinson Cycle Engine

The Atkinson cycle engine is an internal combustion engine. It was designed by James Atkinson in 1882. The essence of the engine is to achieve higher combustion efficiency, that is, lower fuel consumption.

This type of combustion differs from the normal Otto cycle by the longer opening of the suction valve, which extends into the compression phase when the piston rises and compresses the mixture. This leads to the fact that part of the already sucked-in mixture is pushed out of the cylinder back into the suction pipe. Only after this does the intake valve close, that is, after the fuel mixture is sucked in, followed by a certain "discharge" and only then the usual compression. The engine practically behaves as if it had a smaller displacement because the compression and expansion ratios are different. Continued opening of the suction valve reduces the actual compression ratio. As already mentioned, this form of combustion allows the expansion ratio to be higher than the compression ratio while maintaining normal compression pressure. This process is beneficial for good combustion efficiency because the compression ratio in gasoline engines is limited by the octane rating of the fuel used, while a higher expansion ratio allows for longer expansion times (burn time) and thus reduces exhaust gas temperatures - higher engine efficiency . In fact, higher engine efficiency leads to a 10-15% reduction in fuel consumption. This is achieved through less work required to compress the mixture, as well as lower pumping and exhaust losses, and the aforementioned higher nominal compression ratio. On the contrary, the main disadvantage of the Atkinson cycle engine is the low power in liters, which is compensated by the use of an electric motor (hybrid drive) or the engine is supplemented by a turbocharger (Miller cycle), as in the Mazda Xedos 9 with engine. engine 2,3 l.