Abstract: An exhaust braking system used with an internal combustion engine has an inlet valve an exhaust valve, an exhaust brake connected in an exhaust system connected with the exhaust valve, and an actuator connected in a fluid circuit with the exhaust brake. The exhaust brake is closed to retard the rotational speed of the engine and an induction valve connected in an induction passage to the inlet valve and in the fluid circuit with the exhaust brake is also operated to facilitate engine speed retardation. Timing apparatus is connected with the induction valve and exhaust brake to ensure the exhaust brake is closed no later than the closing of the induction valve, while a non-return valve is connected in the induction passage to facilitating an increase in pressure within a piston cylinder of the engine and hence increase the engine retardation. A pressure sensitive device connected in the induction passage or exhaust system controls the maximum pressure of the braking system.

Abstract: The invention provides an automatic exhaust brake valve unit having a hollow body with an exhaust gas passage extending therethrough and a valve closure member movable in the hollow body between a closed position in which it closes the passage, and an open position in which it leaves the passage clear, the hollow body having an open end face closed by a removable plate so that the valve closure member can be removed through that end face. Such a valve unit is usable to control exhaust gas flow in either direction through the exhaust gas passage when connected in an exhaust system of a motor vehicle.