I tried to Google engine brakes after seeing all the avoid use of engine brake signs and now I’m more confused. Can someone explain what engine brakes are, what Jake brakes are (if they are different), and why they are loud. Thanks.
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Typically automobiles are propelled by internal combustion engines, machines where a fuel is mixed with air and burned to produce a controlled explosion. That explosion takes place in a sealed container, a “cylinder”, and the force of that explosion pushes a piston to provide the motive power to the engine. Broadly speaking the process happens in a series of four steps: **Suck, squeeze, bang, blow.** The engine sucks air into the cylinder along with fuel, squeezes that mixture down into a more compact state, ignites it to cause the explosion (bang), and then blows the exhaust out of the cylinder to ready it for the next cycle. Compressing the air is called the “compression stroke” and extracting the power from the expansion of the explosion is the “power stroke”.
A Jake brake (or engine brake) changes this basic process by opening the exhaust valves right before the compression stroke ends, releasing the energy used to compress it and slowing the engine. Since the engine is connected to the wheels by the drive train this results in the vehicle slowing as well (assuming it is in gear). This is in contrast to a normal brake which is just creating friction by squeezing brake pads onto a rotor. Unfortunately releasing high pressure air straight out of the cylinders is very loud, like popping a balloon.
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