What Is Engine Braking? Jake Brake Defined

The generic trademark name for a compression release engine brake, a Jake Brake is most commonly used in large diesel engines on semi-trucks. Derived from Jacobs Vehicle Systems, Inc. (Jacobs), it is an extra supplement to the friction brake system on wheels. Using an air compression and release mechanism, the engine itself works to slow the vehicle.

Semi Truck Tractor Engine

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How Does a Jake Brake Work?

Jake brakes help to reduce speed and many truckers use them on downhill grades and on highway off-ramps where not prohibited. A driver activates the Jake Brake by removing any application of gas to the engine, flipping the engine brake switch — often included on modern manual gear shifts — and allowing the vehicle to slow.

How Does An Engine Brake Work? A Simple Explanation of Jake Brake Mechanics

Jake Brake Einstein Explains

During standard operation of a big rig, air will be forced into the engine cylinders as it enters the intake valve. When this happens, the air gets compressed, converting it to energy for distribution.

From here the pistons take over and guide that energy to the rest of the vehicle to produce power for the semi-truck.

When it’s time to use the jake brake and engine braking systems, the driver will flip the engine brake switch. Once again, air is forced into the cylinders as it enters through the intake valve.

But this time, the jake brake sends a signal to those cylinders and says, “Hey, I’m gonna give you all this compressed air energy, but do not let those pistons send it down to the wheels or to the vehicle. Instead, we’re gonna push that compressed air and all its energy out through the exhaust valves.” When this happens, the result is a short but loud roaring sound and a vehicle that begins to slow down without the use of wheel friction braking systems.

what is a jake brake? definitions from Isaacs & Isaacs
Engine Cylinders Pistons & Valves

Forms of Jake Brake Also Used:

  • Jacobs Brake
  • Jake Nett Braking
  • Jake
  • Compression Release Engine Brake

Examples of Jake Brake Used in a Sentence

  • I gotta quit smokin’ the brakes down the mountain and will just let the Jake Brake do about 90% of the workload as we slowly coast to the base.
  • Hey man, we’re in the parking lot of a truck stop and that sucker’s got quite a roar. You really think you need your Jake on here?No Jake Brakes Sign

No Engine Brake Signs – “Trucks: Please No Jake Brake”

Jake Brakes use a very loud method for slowing the vehicle. What does a jake brake sound like? Some have described the engine braking sound as:

  • A very loud bark of the engine
  • The firing of a gun
  • “The terror of all terrors, jake braking in the middle of the night” Citation1

Among truckers, the engine brake sound sometimes gets celebrated as a point of pride like in this Jake Brake Sound Video below. Be sure to hear that roar at 1:13.

 

 

 

Engine Braking Prohibited in Some Communities

For a growing number of communities, the jake brake noise has proven too disruptive. Some note that when the engine brake is used, “Noise and vibrations from the big rigs damage foundations of houses and other structures near the roadway.”2 According to the Office of Legislative Research (OLR), several states and specific municipalities now have laws in place to prohibit the use of jake brakes.3

Where toll stations exist near residential neighborhoods, this has become more common. There are often exceptions for emergency use. The OLR notes that. “While some place restrictions on the

Jake Brake Meme

use, many states require or permit brake retarder use by certain vehicles or in certain situations.”

Also check out these popular trucker glossary terms:

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References:

1. [https://www.delawareonline.com/story/news/2017/04/25/tractor-trailer-jake-brake-law-difficult-enforce/100874500/]

2. [Ibid]

3. [https://www.cga.ct.gov/2004/rpt/2004-r-0741.htm