what exactly is "engine braking"? i see signs that forbid it on some roads.?

Question

maybe 3 roads in my life that i can remember ever seeing these signs.

lots of answers! thanks to all for answering!

Answer 1

it's when a semi truck down shifts to slow down other then using the air brakes, also known as jake brake, it makes a very loud sound when the semi engine breaks, kinda like a baffleing sound

Answer 2

Big trucks, especially 18 wheelers have several braking systems in addition to the regular brakes to help slow them down. One of them is called the jake brake. When a truck driver activates the jake brake, whenever he/she lets off the accelerator, it activates. This activation prevents one valve from closing in each cylinder. There is an intake valve and an exhaust valve. During normal operation, the exhaust valve closes, and the intake valve opens, allowing diesel fuel and air to be mixed and sprayed into the cylinder. Then the intake valve closes, while the piston is raising, compressing the diesel fuel/air mixture. It compresses to approximately 20 to 1, when it explodes, forcing down the piston. The exhaust valve then opens, allowing the spent fumes to escape and eventually come out of the exhaust pipe. With the jake brake in operation, both valves remain open, which prevents the diesel fuel/air mixture to compress.
The result is that the truck's engine makes a really loud rumbling noise. The next time you see one of those signs, look where you are. they are usually located at the entrance to a town, especially in the residential area, and at the bottom of hills, where the drivers most often have the jake brakes on. The purpose for the signs is to tell the drivers of the trucks not to activate the jake brakes in those areas, because there always seems to be more trucks on the road at night, which would cause people to be awakened.

Answer 3

Engine braking is the act of using the energy-requiring compression stroke of the internal combustion engine to dissipate energy and slow down a vehicle. Compression braking is a common legal term for the same mechanism. Large trucks use a device called an engine brake to increase the effectiveness of engine braking.

Answer 4

Diesel trucks and semi's have a device that helps them to slow down without using the brakes so much and it uses the compression of the engine to slow down the truck except it's very loud and noisy when it vents the compressed air pressure to do this and in some towns is forbidden for that reason.

Answer 5

engine braking, or "jake" braking, involves a bypass valve that allows the intake to readmit exhaust back into the intake.because the air is already burnt it cant allow for proper combustion,thereby forcing the engine to lag.the lag will then slow down the vehicle via the drive train,instead of using service brakes. no downshifting is required.

Answer 6

Trucks with diesel engines have a device that chokes off the exhaust causing the engine to drag and slow the truck down. It saves the air brakes but is very noisy so some towns prohibit them.

Answer 7

i've seen them too!!! no one can ever answer my question tho. i think its some type of emergancy brake for trucks. thats my guess at least. the one road i have seen that on is a really sharp turn on a hill, and there is a road sign of a truck with one sides wheels off the ground and the "no engine brakes" sign right under it.

Answer 8

If you have an a standard transmission and you're going down a hill, you can put the car or truck into a lower gear, thereby making all the power train parts (from the transmission to the universal gears) to move faster (ie: work harder). By leaving it in a lower gear and not feeding the engine any gas, the engine revs higher but it slows the car or truck down. That's engine braking. The danger is that if you over-rev your engine on a really steep hill, you can blow your motor, spill oil on the hill, and kill more people than just yourself.

Answer 9

That is dropping your transmission down a gear or two and allowing you engine to keep the speed down, on a tractor trailer rig they have what is called a a'jake' brake, this releases compression in their engines and makes a loud obnoxious noise. This is probably why they posted it because the jake is only supposed to be used on graded hills for safety to keep from wearing your brakes out. Some just use them for fun and think they sound cool.

Answer 10

Engine braking is the act of using the energy-requiring compression stroke of the internal combustion engine to dissipate energy and slow down a vehicle. Compression braking is a common legal term for the same mechanism. Practically, its occurs when you shift into a lower gear, your speed is reduced.
Engine braking is always active in all non-hybrid cars with an internal combustion engine, regardless of transmission type. Engine braking passively reduces wear on brakes and helps a driver maintain control of the car. It is always active when the foot is lifted off the accelerator, the transmission is not in neutral, the clutch is engaged and a freewheel is not engaged. This is often called engine drag.
Compression braking, a form of engine braking, produces extreme amounts of noise pollution if there is no muffler on the exhaust system of the engine. Use of an engine brake produces similar effects, due to release of compressed gasses, but the mechanism is distinct from regular car engine braking. Anecdotally, it sounds similar to a jackhammer, however the loudness is between 10-20 times the perceived loudness of a jackhammer. Numerous cities, municipalities, states, and provinces have banned the use of unmuffled compression brakes.

Answer 11

Engine braking is used by large diesel trucks to slow down , it is accomplished by using the engine compression to slow the vehicle down whereby saving on brake shoe wear....