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What is an engine brake? Simply defined, it’s the process of slowing down a vehicle by stepping off the accelerator and downshifting gears instead of pressing on the brake pedal.
The braking system on a vehicle is responsible for slowing it down while driving. We rely on the brakes to work every time we step on the pedal. This can eventually cause wear and tear to the system.
But did you know there’s a different way to engine brake that can help extend the life of these components? This method is known as engine braking, and although it’s less commonly used than a foot brake, it’s something that can help improve a vehicle’s efficiency.
Keep reading to learn more about how this braking technique works!
When the accelerator pedal gets released, the air intake valve is closed and a vacuum is created, which prevents air flow from getting to the cylinders. There’s a decrease in energy that starts to create a braking force, which helps slow down a vehicle by lowering the engine speed, or RPMs.
Resistance in the engine is transferred through the drivetrain to the wheels. Some of the braking force produced is from friction in the drive train, but most of it is caused by the vacuum that was created from the lack of air.
The result is a process that helps slow down a vehicle without the use of a footbrake.
There are a few steps to take when it comes to engine braking, and it might take a few attempts to get the hang of it at first. One of the most important things to keep in mind is your safety when engine braking, which is why you should practice on flat, uncrowded and dry roads at first!
Engine braking is done differently depending on the transmission a passenger vehicle has, and is more commonly used on vehicles with a manual transmission.
For a gradual slowdown, it requires taking your foot off the accelerator and shifting into a lower gear, then slowly releasing the clutch. It’s important to let the vehicle slow to a proper speed and shift down one gear at a time.
This will start to slow the vehicle down and allow you to avoid having to step on the brakes. Then, you can stop the car safely using the clutch and brake to minimize the amount of wear. It just takes timing and the knowledge of your car’s gears and rev ranges to perform this stopping technique safely and effectively.
Engine braking on a car with a standard automatic transmission is less common, though it can be done by switching from drive to the available range of lower gears.
Keeping your vehicle in a low gearing helps to get the speed of the vehicle down as you let your foot off the gas pedal. This should not be done when the vehicle is at speed, but shifting to a lower gear can be done before going down a mountain or a hill.
Some automatic transmissions do allow drivers to change gears with either a lever or a paddle shifter. To engine brake in this case, the driver simply has to downshift to a lower gear that will allow the vehicle speed to go down.
Engine braking, also known as compression braking, is a process that can also be used on larger commercial vehicles. The process works a little differently, and there is a diesel engine-specific braking system known as a Jacobs brake (or jake brake) that helps with the process.
A substantial percentage of line-haul semitrailer braking requires air application pressures of 20 psi (air pressure) or less. This means that for the majority of vehicle braking requirements, less than one-fifth of the system’s potential might be used. The air brake system on a line-haul semi is responsible for brake applications numerous times per day.
The objective of compression braking with these types of vehicles is to supplement or relieve the vehicle braking system of some of its light-duty application. Jake brakes assist the vehicle’s service brakes in slowing the vehicle to a stop, thus greatly extending the life of the vehicle’s foundation brakes.
The system works when the driver presses a button on the dashboard, which shuts off the fuel to different cylinders. This stops the combustion process, and exhaust valves are opened to release compressed air from the cylinders. Mechanical drag is generated that helps slow the vehicle.
Large vehicles like semis carry a lot of extra weight, which makes it harder for them to slow down. Utilizing jake brakes can help these vehicles slow down more quickly and prevent wear and tear on the regular braking system.
You might be wondering, “Is engine braking bad for my engine?” While the process does generate some heat, this is minor and doesn’t have any negative effects on the vehicle. If downshifting is done properly, your transmission should be fine.
There are several benefits to engine braking, including:
If hearing about engine braking has you curious about the different car braking systems and stopping methods, you could expand your knowledge by enrolling in the Automotive Technology program offered at Universal Technical Institute (UTI).
You can graduate in less than a year7 with the hands-on experience and training needed for an entry-level career in the industry.1 Courses in the program cover a range of topics, including vehicle braking systems.
Want to find out more? Request more information online or by calling 800-834-7308 to get in touch with an Admissions Representative today.
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Ever wondered how diesel exhaust brake systems work? Click here to read our complete guide.
1) UTI is an educational institution and cannot guarantee employment or salary.
2) For program outcome information and other disclosures, visit www.uti.edu/disclosures.
7) Some programs may require longer than one year to complete.
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