Use of engine brake prohibited
I was driving over a mountain pass in a passenger vehicle between Las Cruces and White Sands and noticed a sign that read "Use of engine brake prohibited." That's the first time I've ever seen such...
Forum Discussion
What is actually banned is the "Jake" or Compression release brake that is un-muffled.
From Wikipedia:
A compression release brake, or Jake brake, this is the type of brake most commonly confused with real engine braking; it is used mainly in large diesel trucks and works by opening the exhaust valves at the top of the compression stroke, resulting in adiabatic expansion of the compressed air, so the large amount of energy stored in that compressed air is not returned to the crankshaft, but is released into the atmosphere.
Normally during the compression stroke, energy is used as the upward-traveling piston compresses air in the cylinder; the compressed air then acts as a compressed spring and pushes the piston back down. However, with the Jake brake in operation, the compressed air is suddenly released just before the piston begins its downward travel. (This sudden release of compressed air creates audible sound waves similar to the expanding gases escaping from the muzzle of a firearm.) Having lost the energy stored within the compressed air, there is no 'spring back' from it so the engine must expend yet more energy pulling the piston back down again. This type of brake is banned or restricted in many locations where people live because it creates a sound loud enough to disturb the peace, including waking people at night. It is very effective however, and creates immense amounts of braking force which significantly extends friction brake life - A 565 hp (421 kW) diesel engine can produce up to 600 hp (450 kW) of braking force.
What is on motorhomes is an "Exhaust brake" which restricts the exhaust from the engine such as by a variable vane turbo or a butterfly valve. These are not banned anywhere.
From Wikipedia:
A compression release brake, or Jake brake, this is the type of brake most commonly confused with real engine braking; it is used mainly in large diesel trucks and works by opening the exhaust valves at the top of the compression stroke, resulting in adiabatic expansion of the compressed air, so the large amount of energy stored in that compressed air is not returned to the crankshaft, but is released into the atmosphere.
Normally during the compression stroke, energy is used as the upward-traveling piston compresses air in the cylinder; the compressed air then acts as a compressed spring and pushes the piston back down. However, with the Jake brake in operation, the compressed air is suddenly released just before the piston begins its downward travel. (This sudden release of compressed air creates audible sound waves similar to the expanding gases escaping from the muzzle of a firearm.) Having lost the energy stored within the compressed air, there is no 'spring back' from it so the engine must expend yet more energy pulling the piston back down again. This type of brake is banned or restricted in many locations where people live because it creates a sound loud enough to disturb the peace, including waking people at night. It is very effective however, and creates immense amounts of braking force which significantly extends friction brake life - A 565 hp (421 kW) diesel engine can produce up to 600 hp (450 kW) of braking force.
What is on motorhomes is an "Exhaust brake" which restricts the exhaust from the engine such as by a variable vane turbo or a butterfly valve. These are not banned anywhere.
