October 26, 2021

Exhaust Braking and How is it Different from Engine Braking

People who use normal petrol and diesel vehicles are usually familiar with rim brakes, drum brakes or disk brakes and if they are advanced drivers then they might know how to use the engine or compression braking.

Larger vehicles especially diesel powered and commercial vehicles such as semitrailers, buses, heavy equipment, and large RVs, that carry exceptional amounts of weight in the shape of cargo has additional and supplemental braking systems. These supplemental braking systems are designed to slow the vehicle in a safe manner instead of completely putting the pressure on normal brakes that can be overwhelmed with weight and trajectory of the road.

In simpler terms, diesel exhaust brakes operate by controlling the exhaust gases and by creating the back pressure within the engine to slow the engine speed.

Why Exhaust Brake is Paramount for Diesel vehicles

Large diesel-powered vehicles cannot rely on the wheel mounted brakes alone. There are supplemental braking systems that help those vehicles to slow down and exhaust braking is one of the most comprehensive and significant way of slowing down those vehicles.

Diesel powered vehicles do not benefit from the same level of engine braking as petrol powered vehicles enjoy. In a typical petrol-powered car, letting off the accelerator or putting it in a smaller gear result in the reduction of the speed due to friction within the car engine and the road. Petrol engine use throttle valve to create a vacuum for the engine to operate against.

A diesel engine operates on the regulation of the fuel rather then the airflow. This is the reason that diesel powered vehicles create more torque and can coast longer when accelerator is released.

Heavier loads on larger diesel vehicles put even more pressure on the braking system that makes supplemental braking even more important.

How Does Diesel Exhaust Brake Work?

Diesel exhaust brake works by trapping the exhaust gases in the exhaust system to create backpressure that renders the engine retard its speed.

Pistons force the by-product of combustion engine i.e., exhaust gases on their way out. When the exhaust brake is applied and the butterfly valve is closed, the engine uses additional force to push the exhaust gases from the engine. This additional force slows the engine’s rotation and slows the engine down which in turn slows the vehicle.  

Now a days, computer control exhaust brake systems are in place that regulates the exhaust brakes way better then the conventional exhaust braking systems and make it way smoother and efficient.

Difference Between an Engine Brake and An Exhaust Brake?

Engine braking is usually reserved for petrol vehicles as they use throttle valve and regulate the fuel to slow down the vehicle while the exhaust brake uses the butterfly in the exhaust to regulate the exhaust gases and create back pressure to slow down the vehicle and exhaust brake is usually reserved for heavily loaded deisel vehicles.

Benefits of Exhaust Brake System

Exhaust brake system is widely used in almost all heavy-duty diesel vehicles for very good reasons. Supplemental braking is the reason why conventional braking is not at breaking point and diesel-powered vehicle gain lots of additional benefits. Following are some of the benefits of exhaust braking.

Help Decelerating the Vehicle

Diesel powered vehicles that have enormously heavy loads on them can always use a bit of supplemental braking. Normal braking is not as effective when the road is inclined downwards and exhaust braking benefits and helps the vehicle to decelerate faster.

Control Downhill Speed

Heavy commercial vehicles can benefit from exhaust brake as it not only helps to stop the vehicle early but also helps control the downhill speed as well.  

Lower Brake heat

Supplemental exhaust heat can be beneficial in reducing the brake heat as the complete braking load that is otherwise be put on the conventional braking is distributed with the help of exhaust braking.

Less Brake Wear

Brake wear can be an extremely dangerous aspect of downwards decent for heavily loaded vehicle and exhaust braking can prove to be a blessing as it ensures less brake wear and safe descending.

Extra braking Reserve

Heavy duty diesel vehicle can neither depend on the conventional braking alone nor it can depend on engine braking. So, extra braking reserve comes in the form of exhaust braking to either decelerate or stop the vehicle.

No Extra Noise

We are all familiar with the engine braking and the noise that it creates. Some residential areas with roads leading to a downward slope have banned the engine braking due to its noise. Exhaust braking on the other hand, produce no additional noise while helping to slow down the vehicle.

Prolonged Lifespan of Conventional Brakes

Fully loaded heavy duty vehicles are a great help to the normal braking system and can increase the life span of the conventional braking system.

Disadvantages of Exhaust Brakes

Surprisingly, there are no known disadvantages to the exhaust brakes system. In fact, it is recommended to the truckers to add the exhaust braking system since those heavy-duty vehicles can always welcome supplemental braking systems.

Do Exhaust Brakes Make Noise?

While engine braking and compression braking makes a lot of engine noise, exhaust brake make absolutely no additional noise and helps the vehicle slow down without any additional danger to any other part of the vehicle.

Does An Exhaust Brake Use More Fuel?

Exhaust brake works by limiting the release of exhaust gases from the engine, hence slowing down the engine which may help saving the fuel instead of using more fuel. So no, exhaust brake uses absolutely no extra fuel at all.

When Should You Use an Exhaust Brake?

Exhaust brakes are most efficient on the bigger commercial vehicles and especially when they are fully loaded and are descending a hilly road. This is when an additional or supplemental braking system is most helpful to the conventional braking system and makes a real difference. Exhaust brakes are integral part of heavy-duty vehicles and are recommended to be added in every vehicle that uses heavy loads.