Engine braking system using spring loaded valve

An engine braking system comprising:

• an exhaust control path between an engine cylinder and an exhaust discharge path;
• a valve element located within the path, the valve element operable between a closed position to close the exhaust control path and an open position to open the exhaust control path;
• a spring urging the valve element toward the closed position;
• a retainer arranged to be positioned in two operating positions, a first operating position which prevents opening of the valve element and a second operating position which allows opening of the valve element;
• and
• a wedge operable to move between a first position and a second position to move the retainer between the first and second operating positions wherein the at least one face comprises a first surface having a first surface area subject to cylinder pressure when the valve element is in the closed position, and the valve element comprises a second surface set back from the first surface and having a greater surface area than the first surface area, the second surface subject to cylinder pressure when the valve moves toward the open position.