The exhaust brake restricts the flow of exhaust
gases. The restriction compresses the exhaust gases. The compression of the
gases creates a back pressure that slows the vehicle with the engine and
the transmission. A small opening in the butterfly valve performs the following
functions:
| • | Prevents the buildup of excessive exhaust system pressure |
| • | Protects the engine from damage when the exhaust gas flow level
is high |
The following actions occur simultaneously during operation:
| • | Air at line pressure is directed to the exhaust brake actuator. |
| • | The fuel supply to the engine returns to an idle condition. |
The air pressure in the actuator pushes against the actuator return
spring. As a result, the return spring is overcome. This action causes the
following results:
| • | The push rod rotates the butterfly valve to the closed position. |
Rest condition occurs when the air supply to the actuator is removed.
The following actions occur during rest condition:
| • | The actuator return spring retracts the push rod. |
| • | The butterfly valve returns to the open position. |
| | This position enables unrestricted flow of the exhaust gases. |
| • | The fuel supply to the engine is restored. |
