Why prohibit engine braking?

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Completely different thing! They are referring to the "Jake Brake" in heavy trucks, where the trucker opens a portal to the depths of Hades and you hear a very loud

BrapBrapBrapBrapBrapBrapBrap

sound, wrap the pillow over your ears, and call the Realtor in the morning.

This does not apply to regular old downshifting in a gasoline car, where you spin the engine to use your cooling system as a dynamic brake. If trucks would just do that, nobody would complain.

The Jake Brake (or more properly the Jacobs brake) makes engine braking more efficient. Normally a diesel gulps a full load of air (no throttle plates) and no fuel is injected when it is in engine braking. The engine consumes energy in the compression cycle but regains that energy in the expansion (normally power) cycle. The Jake Brake prevents that regain, by opening the exhaust valve at the start of the power cycle instead of the end. This instantly, and percussively, dumps a shot of 200-400 psi air directly out the exhaust stack.

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Although the signs often refer to engine braking in general, they are actually intended to prohibit the usage of compression release engine brakes. These braking systems, commonly found in diesel engines of heavy vehicles, are more effective than simply braking with an idle engine but can generate excessive noise. Prohibiting the use of such braking systems aims to reduce noise pollution in urban areas.

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I have always been told that the reason for this is because engine braking is noisy[1], and therefore considered undesirable in built-up areas.

In New Zealand, there are signs that say "Heavy Vehicles Please NO Engine Brakes NEXT 4 km" because these vehicles are much louder than typical cars.

[1] More information on engine braking noise in New Zealand

About me

Hello,My name is Aparna Patel,I’m a Travel Blogger and Photographer who travel the world full-time with my hubby.I like to share my travel experience.

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