What is Jake Braking
I guess we are going to have to go back to the basics here, and “Officially” explain what a “Jake brake” is, and what “Jake braking” is.
Some “Store bought truck drivers” bless their hearts tried to explain to someone on twitter.
This is what I read for the answer given on twitter, “It is a very loud, but helps us to stop. Hard to explain”. This was from another twitter “trucker”, “Brakes won’t stop us we need the Engine Brake or we keep on Trucking.” Nope, unfortunately both the twitter “truckers” are wrong.
The only reason a “Jake brake,” engine brake or engine retarder or exhaust brake would be loud is because the muffler or exhaust pipe is burning/burned out. Or you are running a set of “straight pipes” with no mufflers. The loudness has no effect on stopping. If it did, then the louder it was the better you would stop.
There are two types of “Jake brakes” one is a engine retarder and the other is an exhaust brake, both essentially work for the same purpose, but work entirely different.
An exhaust brake is a means of slowing a diesel engine by closing off the exhaust path from the engine, causing the exhaust gases to be compressed in the exhaust manifold, and in the cylinder. Since the exhaust is being compressed, and there is no fuel being applied, the engine works backwards, slowing down the vehicle. The amount of negative torque generated is usually directly proportional to the back pressure of the engine.
The term “Jake brake” comes from a Jacobs Engine brake, or engine retarder. It works when exhaust valves in the cylinder head open, releasing the compressed air that is trapped by the head and slows the truck down. When the accelerator is released on the truck, its forward momentum continues to turn the Diesel engine’s crankshaft. That intern compresses air in the cylinder.
As the piston passes through top dead center, the compressed air in the cylinder acts as a spring and pushes the piston back down the cylinder. It returns most of the energy expended in compression back to the crankshaft. This causes the truck to slow down, without the use of the service brakes.
A “Jake brake” is used along with gearing down the truck to keep from overheating the service brakes that are used to stop the truck. Although some trucks are not equipped with an engine retarding system, so gearing down and using the service brakes is required in order to slow or stop.
When a truck’s service brakes are glazed over, this means that they have been very hot, and usually it will make the driver seem he/she has no brakes. Glazing is the hardening of the brake lining, and the only to fix them is to replace or grind the glaze from the lining. The term “Jake braking” is what happens when a driver is using the engine retarder to keep from using the service brakes. Or some truckers say: “I’m saving my brakes, by using the Jake brake.”
When the exhaust system on a truck is in proper working fashion, you barely can even hear the engine brake. But, thanks to “Jake brake cowboys” most communities have added no “Jake brake” use laws. So, the trucks have to comply and use the service brakes on the trucks, in order to slow down and stop. Fines vary from city to city, but I have seen them as high as $400.00.
© 2010 – 2011, Truck Drivers News Blog. All rights reserved.