The principle behind the Jacobs Engine Brake TM engine retarder is simple. In order to understand how the Jacobs Engine Brake TM retarder provides its strong retarding power, let's compare the engine cycles with and without a Jacobs Engine Brake TM . For this purpose, the illustrations pertain to a four-cycle engine. The intake valve opens and air is forced into the cylinder by boost pressure from the turbocharger.
Air is compressed by the engine piston.
The energy required to compress this air is produced by the vehicle's driving wheels. Essentially no energy is absorbed and no net retarding work is done. The intake valve opens and air is forced into the cylinder by boost pressure from the turbocharger. Air is compressed to approximately 500PSI by the engine piston. The energy required to compress this air is produced by the vehicle's driving wheels.