Hydraulic circuit for unlocking variable compression ratio connecting rod locking mechanisms

1. Field of the Invention A variable length connecting rod () has a first locking mechanism () for releasably locking connecting rod parts in a first effective length setting (FIG. ) for the rod, and a second locking mechanism () for releasably locking the connecting rod parts in a second effective length setting to change the compression ratio for an engine cylinder. When a length change is to be made, hydraulic fluid unlocks a locked one of the locking mechanisms, allowing inertial force to effect the length change during an engine cycle. At completion of a length change, the other locking mechanism automatically unlocks.