The Jacobs Engine Brake (Jake Brake) is a clever invention based on very simple mechanical principles. Originally invented by Clessie Cummins, the Jake's function effectively removes the power stroke from a four stroke engine cycle.
In a four stroke engine, the power stroke is followed by an exhaust stroke, intake stroke and then compression stroke with each of these, most notably the compression stroke, requiring input of substantial energy from elsewhere within the engine system before it can be completed.
The engine could not operate unless that lost energy, and a great deal more, was recovered during the subsequent power stroke - when the piston is forced downwards by rapidly expanding hot gases - the consequence of the controlled combustion processes central to the principles of the internal combustion engine.
The Jake Brake consists of a mechanical/hydraulic assembly mounted above the engine rocker levers and a suite of elementary electrical controls. A common oil galley connects two hydraulic pistons with one positioned above the exhaust valves and the other above the mechanical injector rocker lever.
Through a closed system involving an electronic solenoid and a check valve, the exhaust valves are forced open into a compressed engine cylinder just at the point when injection commences. This "dumps" the cylinder pressure (and hence temperature) essential for the auto-ignition of the introduced fuel from the fuel injection system. The result is that the power stroke becomes defunct and the engine is left with a succession of parasitic cycles which together produce a net braking effort of very substantial proportions. The repetitive and explosive release of high cylinder pressure into the exhaust system is what causes the familiar Jake Brake noise as trucks are slowing down or descending hilly terrain.
Torquepower also markets a Donaldson muffler, called "Silent Partner" that is designed specifically for Jake equipped engines to reduce the noise created during the braking cycle. Contact us for your Jake requirements including Genuine Jake manuals.
