Engine brakes have not always existed. In fact, they appeared almost 65 years after the first working diesel engine. And since their introduction, they have become a staple in larger diesel engine applications. Engine braking grew out of a rocky beginning dating back to 1931, when Clessie L. Cummins and his team had a near-death experience. This experience got him thinking about how to use the engine both as a means of propelling a vehicle uphill and to better control it on steep grades. In 1957, he came up with the idea of ​​using pre-existing but modified components to open the exhaust valve. The idea was so unprecedented that it resulted in a broad and powerful patent being filed to cover the idea. (About us: Jacobs Vehicle Systems) Early versions of engine braking crudely used injector movement to achieve the goal of slowing the engine. And finally, it was realized that the hydraulic operations of the system would be much more efficient and practical. These internal engine retarders, more commonly called decompression brakes, worked on the idea that to control power and slow the vehicle, the engine could vent compressed air before igniting. And help slow the engine by removing a power stroke. The downside is that the exhaust becomes very noisy and is therefore prohibited for use in most towns and cities. Engaging or activating the engine brake is very simple. Once the diver turns the system on using a switch, the solenoids activate and lock the cylinder valve stem. Thus allowing the valve to be opened by the cam and exhaust the compressed air through the exhaust. Many systems incorporate a switch that is not turned on...... middle of paper......the crank turns, it transfers power to the vanes in the housing. Which are located on the unit housing, creating a fluid drag that absorbs power and slows the vehicle. (Truck Troubles.com) Activation of this style of retarder is accomplished by filling the chamber that contains the rotor and housing vanes with oil. Once the chamber is filled, the rotor and vanes hydraulically engage and slow the engine. When the engine slows down, a valve regulates the amount of oil in the chamber to help maintain consistent stopping power, which is based either on driver input or peaks when the clutch and throttle are engaged. released. The oil used in this system is under pressure to control the braking power applied. Higher pressures result in higher braking. While lower pressures result in lower breaking power. (TruckTroubles.com)