Editing Miller cycle (section)

===Compression ratio===
Efficiency is increased by having the same effective compression ratio and a larger expansion ratio. This allows more work to be extracted from the expanding gases as they are expanded almost to atmospheric pressure. In an ordinary spark ignition engine at the end of the expansion stroke of a wide open throttle cycle, the gases are at around five atmospheres when the exhaust valve opens. Because the stroke is limited to that of the compression, still some work could be extracted from the gas. Delaying the closing of the intake valve in the Miller cycle in effect shortens the compression stroke compared to the expansion stroke. This allows the gases to be expanded to atmospheric pressure, increasing the efficiency of the cycle.