Compression release engine brake

A compression release engine brake from Jacobs Vehicle Systems, popularly known as a "Jake brake"
A view of engine compression brake rocker arm (the thinnest arm at the left of each set)
Jacobs Engine Brake Division logo

A compression release engine brake, compression brake, or decompression brake is an engine braking mechanism installed on some diesel engines. When activated, it opens exhaust valves to the cylinders, right before the compression stroke ends, releasing the compressed gas trapped in the cylinders, and slowing the vehicle.

Clessie Cummins was granted a patent for the engine compression brake in 1965, and the first company to manufacture them was Jacobs Vehicle Systems.[1][2]

  1. ^ US patent 3220392, Cummins, Clessie L., "Vehicle engine braking and fuel control system", issued November 30, 1965 
  2. ^ "Jacobs® Engine Brake Retarder" (PDF). The American Society of Mechanical Engineers. October 17, 1985. Archived from the original (PDF) on 2011-08-16. Retrieved 2010-04-30.

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