Algodoo

This would be the linkage to use if you were to build a fuel engine based on the Atkinson Cycle (as opposed to the Otto Cycle). The Atkinson Cycle differs from the Otto Cycle in two ways:

The exhaust stroke is longer than the intake stroke.
The power stroke is longer than the compression stroke.


This linkage here allows both of these to happen. Notice that as the purple bar is pointing upwards, the piston doesnt move as far. Those two strokes are the intake and compression.When the bar points downwards, those two strokes move more and are used as the power and exhaust stroke.
Since there is less intake, the Atkinson cycle is more efficient at the expense of power. If an Atkinson engine was made to run on as much fuel as a conventional 4 stroke engine, it would have far more power if they had the same compression ratio. The difference is the expansion ratio during the power stroke. The Atkinson cycle does not suffer as much power loss due to the shorter compression and therefore less pumping loss. Since the expansion ratio is greater, Atkinson engines have lower exhaust temperature and less harmful pollutants because the power in the engine does not come from the burning of fuel, but the expansion of the hot exhaust.