[sharpneli]

Not just that. It does require Atkinson cycle to reach the efficiencies they have. It just means that the compression stroke is shorter than the power stroke.

Basically with that cycle they can get massive compression ratios. As an example newer Toyotas are at 14:1 ratio with 41% thermal efficiency. That’s close to diesel territory on a gasoline car.

Naturally when you floor it it goes to Otto cycle and efficiency drops.