What Is Engine Braking and How Does It Work?

What does it mean to 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 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!

How Does Engine Braking Work?

When the accelerator pedal gets released, the air intake valve is closed and a vacuum is created, which prevents airflow into 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 RPM.

Resistance in the engine is transferred through the drivetrain to the wheels. Some of the braking force produced is from friction in the drivetrain, 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 foot brake.

READ MORE: How Do Car Braking Systems Work?

How to Engine Brake

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 to start!

Engine braking is done differently depending on the type of transmission a passenger vehicle has and is more commonly used on vehicles with a manual transmission.

For a gradual slowdown with a manual transmission, 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 and allow you to avoid having to step on the brake pedal. 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.

Switching your vehicle to a lower gear 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 needs to downshift to a lower gear that will allow the vehicle to slow down.

When To Use Engine Braking

Engine braking is particularly effective and beneficial in scenarios where maintaining control and safety are paramount, such as during long descents on steep hills or mountains. By shifting to a lower gear, the engine's speed is increased while the vehicle's speed is controlled without solely relying on the brakes.

Additionally, engine braking is useful in slippery or wet conditions as it allows for smoother deceleration, reducing the risk of skidding compared to sudden braking with the brake pedal.

Drivers should be aware of their surroundings and ensure the use of engine braking is communicated through brake lights if the vehicle does not automatically signal deceleration to keep other traffic on the road informed.

Jake Brakes

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 (pounds per square inch) 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.

Benefits of Engine Braking

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:

• Lower associated maintenance costs: Reduced foot pedal applications result in less wear and tear on the foundation brake components, extending the life of those components.
• Safer downhill driving: Prevents excessive friction that can cause brake fade and brake failure, which can cause the driver to become unable to safely stop the vehicle.
• Improved fuel efficiency: Since the ECM shuts off the fuel supply to the injectors for the cylinders used during compression braking, this process does in fact slightly help with the overall fuel efficiency of the engine.

Engine Braking FAQs

Does engine braking save fuel?

Engine braking can save fuel under certain conditions. When a vehicle employs engine braking, the driver lifts off the accelerator and downshifts the transmission, which reduces the fuel supply to the engine.

What are the safety considerations when using engine braking?

It’s important to understand how engine braking affects vehicle control. The technique can increase the load on the drivetrain and potentially lead to reduced traction, which may result in skidding or loss of control. Additionally, because engine braking does not activate the brake lights, other drivers may not be aware that the vehicle is slowing down, increasing the risk of rear-end collisions. This is why it’s important to tap the brake pedal intermittently to signal to following drivers that you are reducing speed.

What maintenance is associated with engine braking?

Regular maintenance is crucial when frequently using engine braking. Primarily, engine braking increases the workload on the transmission and drivetrain. Therefore, these systems require periodic checks and maintenance to ensure they operate efficiently and prevent premature wear. Adhering to the manufacturer's recommended service intervals is good practice!

Learn About Braking Systems at UTI

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).¹

You can graduate in less than a year with the hands-on experience and training needed for an entry-level career in the industry.^7,18 Auto 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.