If you tow you should know what engine braking is. Even if you don’t tow, there are reasons and benefits to using it even in your car. Engine braking, also known as “retarding an engine,” is a method used to slow down a vehicle without using the traditional friction brakes. Instead, the engine slows the vehicle by decreasing the power output and increasing the drag force.
With many years on the road full-time we have a lot to share on this topic. There are several types, each with its own unique features and benefits. We’ll discuss the different types, the benefits of using it, and other important facts about this technology.
What Is Engine Braking?
Engine braking is a process by which an engine can decrease its power output and reduce speed. This method of slowing down a vehicle does not use the brakes and can have alot of benefits. It can save fuel, provide better control, and increase safety.
The basics of how you use engine braking is by downshifting the vehicle while at speed to rev the engine up. Then release the gas peddle and allow the engine RPMs to decrease and slow down the vehicle. You can think of it like using the engine backward. Just like how the RPM starts low and then goes up while accelerating when the engine braking you start high and let it slow down.
The mechanics of how engine braking is going to depend on the type of engine used as diesel and gas engines are different. We will dig into the different types of engine brakes a little later.
What Are the Benefits of Engine Braking?
There are several benefits to engine braking. While it may help increase fuel efficiency, the key benefits are improving safety and reducing maintenance costs.
Engine braking is a great safety feature for drivers. It adds additional stopping power to large vehicles such as trucks and buses. This can help slow a heavy load better than just using the brakes.
The biggest benefit for large vehicles is when descending hills or mountains. Brakes get very hot when they are used for an extended period of time and can even start to fail. Using the engine to slow the vehicle it takes some of the load from the brakes. Many trucks can even vary their engine brake and control their speed without using the brakes at all.
Engine braking is an effective way to reduce maintenance costs. By taking on some of the load from the brakes, it reduces wear and tear on brake pads. This helps to extend their life, thus reducing the need for costly replacements.
Additionally, it prevents overheating of the brakes, which can help reduce the risk of damage to other elements in a vehicle’s braking system due to intense heat exposure.
Thus, it offers an efficient and cost-effective way to maintain safety and longevity in your car’s performance.
Are Both Diesel and Gas Engines Capable of Engine Braking?
Kind of, gas engines are naturally capable of some engine braking due to their design. Gas engines have a throttle valve that provides natural backpressure any time the engine is turned over without the gas peddle being applied. Diesel engines however lack this valve. Because of this unmodified diesel engines do not have much if any engine braking capability.
However most large diesel engines add additional components that give them engine braking performance that exceeds many gas engines. These components are designed specifically for the task of adding engine braking because it is so important for heavy vehicles.
However, both types of engines offer advantages such as improved safety, reduced strain on the brakes, and fuel savings when used correctly.
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What Are The Different Types of Engine Brakes
Some engine brake types are exhibited by how you drive a vehicle, while others may include additional equipment. Each provides a similar result, slowing the vehicle while reducing the use of mechanical brakes.
Natural Aspiration Braking
Natural Aspiration braking is the type of engine braking in gas engines that uses the engine’s compression to slow the vehicle down.
All gas engines can do it and it works by letting off the accelerator pedal at high RPM’s, which closes the throttle and creates a vacuum inside the engine. It increases the drag force on the pistons which put negative force on the crankshaft, slowing the vehicle down.
The driver’s shift to a lower gear creates stronger engine braking. Many often refer to this as “gear down” braking. This system is less powerful than other options and you should only use it as a supplement to traditional friction brakes.
Variable Geometry Turbo Braking
Variable geometry turbo (VGT) braking uses the turbine in the turbocharger to slow the vehicle down. In a typical turbocharged engine, exhaust gases flow through the turbine, spinning it and creating boost. In VGT braking, the vanes in the turbine can be adjusted to restrict the flow of exhaust gases, creating backpressure on the engine.
When the driver applies the brakes with the engine brake selected, the engine control unit (ECU) sends a signal to the VGT actuator which will adjust the angle of the vanes, increasing the backpressure and slowing the vehicle down.
This is a common method used in diesel light and medium-duty trucks to add engine braking. Remember that the diesel engine does not naturally have engine braking performance, so this is an easy way to add it.
Compression Release or Jake Brake
Compression Release braking, also known as “Jake braking,” is a method of slowing down a diesel engine vehicle by briefly releasing compressed air from the cylinders. It works by opening the exhaust valves at the top of the compression stroke of the engine, releasing the compressed air in the cylinders. Then with both valves closed the cylinder tries to expand the small volume of air in the chamber. This creates a force pulling up on the piston and slows the vehicle.
When the driver activates the Jake brake, it sends a signal to the engine control unit (ECU) which then sends a signal to the injectors to stop injecting fuel into the cylinder, this causes the engine to stop working as a power source and instead use the compressed air to slow down the vehicle.
When the exhaust valves open, the compressed air in the cylinder is released and the kinetic energy of the engine is converted into heat energy, slowing the vehicle down. Jake brakes are particularly useful for heavy-duty vehicles such as trucks and buses, as they can significantly increase the braking power of the vehicle and reduce wear on traditional friction brakes.
It is worth noting that Jake brakes are not suitable for all vehicles and can be loud, so they are typically used in specific situations such as when driving down steep inclines or when slowing down quickly. In addition, some places and communities may have restrictions on the use of Jake brakes because of the noise. If you have ever seen a sign saying no engine braking it was because of the noise.
Transmission Retarder Braking
A transmission retarder is not technically an engine brake but works in a similar way to slow the vehicle. It works by applying a braking force to the drive shaft, which slows the rotation of the wheels and reduces the vehicle’s speed.
Transmission retarders are typically used in heavy-duty vehicles such as trucks and buses operating in city stop-and-go traffic. The retarder excels in the city because its quicker to engage and fully variable, allowing a vehicle to control its speed with fine precision.
There are different types of transmission retarders but the most common is the hydraulic retarder. It uses a pump similar to a torque converter to create a braking force that is applied to the transmission. The driver can activate the transmission retarder by pressing a button or pedal, and it can be adjusted to different levels of braking power depending on the situation.
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Does Engine Braking Harm Your Vehicle?
Engine braking doesn’t harm your vehicle if it’s in good working order. In fact, it’s simply the opposite of accelerating and puts the same stresses on the drivetrain, only in reverse.
Using it when descending a long, steep hill or approaching a stop sign can save wear and tear on your brake pads, extending their life. It also helps to conserve the vehicle’s energy, reducing fuel usage.
It is possible that hard downshifts or the extra force in the negative direction on the drivetrain can wear some parts sooner. Differential preload and slop are one area we have seen heavy exhaust braking cause wear sooner than if it were not used.
When Should You Engine Brake and When Shouldn’t You?
Engine braking is a great tool for drivers who need to slow down their vehicles in certain situations. It can be especially helpful when descending long hills, controlled highway exits, and in other circumstances where you have plenty of time to slow down.
However, it’s important to note that engine braking is not suitable for stop-and-go traffic or city driving, where consistent and rapid control over your speed is required. In these cases, using the brakes as intended would be appropriate.
Properly using both types is key to ensuring optimal performance and longevity of your car’s engine and braking components.
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Why Do Cities Often Have No Engine Braking Signs?
Cities often have “no engine braking” signs to reduce noise pollution and improve public safety, particularly when that noise is unmuffled.
It can produce loud noises that can disrupt people living, working, or recreating near busy roads. This is particularly true in densely populated areas such as cities, where the close proximity of buildings can amplify these sounds.
Why Is Engine Braking Worth It?
It’s a beneficial technique due to the reduced wear and tear on the vehicle and its braking system, increased safety, and improved fuel efficiency. Cities often have no engine braking signs because of the loud noise associated with it. However, this should not deter people from using this beneficial method of controlling speed when appropriate.
It is particularly worth employing it when descending steep declines, long highway exit ramps, and other lengthy approaches. Learn how to properly use it today to save your brake pads and improve your peace of mind.
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