This is from the Car and Driver Mag
Selectable Squish
Raising an engine’s compression ratio improves fuel efficiency during low-load operation, but it can also lead to catastrophic detonation when maximum power is requested. Engineers have long sought to navigate this challenge with a variable-compression-ratio engine, and Infiniti promises to implement its solution in early 2018 with a complex system of links in the crankcase.
There’s more than one way to skin this cat, though. German powertrain engineering company FEV proposes a piston wrist pin that passes through an eccentric bushing at the top of the connecting rod. As the bushing rotates, the piston moves vertically relative to the rod, in turn adjusting the compression ratio. The position of the bushing is determined passively by a pair of miniature pistons inside the connecting rod that rotate the cam in reaction to combustion and inertia forces. FEV’s 1.7-liter turbocharged inline-four demonstrator can adjust its compression ratio from 8.8:1 to 12.0:1 in 0.2 to 0.6 second.