Is Exhaust Brake Bad For Engine?

By May 30, 2021Exhaust

So, you have an exhaust brake installed on your truck by the previous owner, or you are planning to install an exhaust brake on your truck, and you keep asking yourself the question – is exhaust brake bad for the engine? 

The answer is yes – exhaust brake is not harmful to the engine at all. It is even recommended for truckers to have an exhaust brake.

Mostly because trucks are heavy and need a lot of stopping power to make a full stop – especially during downhill.

Let’s discuss more about exhaust brakes and why they are crucial for your safety (especially for trucks).

5 Reasons Why Exhaust Brake Is Not Bad For Engine

Exhaust brakes will not damage your engine at all and have been used time and time again on trucks. Here are 5 concrete reasons why exhaust brakes will not harm your engine. 

 

1. No direct contact on rods or pistons

During exhaust brakes, there are no direct contacts being made to rods or pistons. The braking effect is produced indirectly by an increase in air pressure. 

Which means, there won’t be any wear and tear damages or direct metal to metal contact that can actually cause damage. 

In fact, exhaust brakes won’t even need maintenance because it does not use any additional tools – just good old air pressure and a valve.

2. Exhaust brakes are not used all the time

Exhaust brakes are only used in certain scenarios where more braking power is required – think downhill scenarios where you are driving downhill with your fully loaded truck and there is a lot of traffic on the road. 

Regular disk brakes will not provide enough force for your truck to make a stop, so the best alternative is to use an exhaust brake.

I have mentioned many times that exhaust braking is not harmful to the engine. The fact that it’s not even used that often should give you an additional peace of mind.

3. Little parts required to work

Exhaust brakes don’t require a lot of additional parts and technologies to work. Mostly there’s an additional exhaust valve which closes when you need to apply the exhaust brake

The valve closing creates an additional back pressure that will flow all the way into the combustion chamber – slowing down the up-and-down movement of the valve to slow the vehicle. 

This means exhaust brakes are simple and do not interact with many other components in this engine. Lesser interaction almost always means a lesser chance for something to break.

4. Truck exhaust manifolds are made to be tough

Exhaust manifolds are tough, they are made from special steel that can withstand a lot of heating-and-cooling cycles as well as the pressure.

Additional pressure created when you apply an exhaust brake can easily reach 60 PSI, and that is a lot of pressure – but since your manifolds are designed to work this way, it will not be damaged when exhaust brakes are applied. 

 

5. Diesel engines are designed with this in mind

Diesel engines are workhorses, and they are meant to be tough. Their block is made from cast iron steel that is extremely tough and able to withstand huge amounts of pressure. 

Their structure is very different from the regular gasoline engines and they are reinforced with heavy-duty parts like heavy-duty pistons and rods, heavy-duty bolts, and much more. Parts that can withstand anything and keep going. 

So, you shouldn’t even worry even a tiny bit that something bad could happen to your engine by applying the exhaust brake.

What Is An Exhaust Brake?

We spoke a whole lot about why exhaust brakes will not damage the engine. But what is it really? And how does it work?

Exhaust brake is a device that helps a diesel engine to make a full stop. Exhaust brake works by using an exhaust valve that closes and creates a major restriction in the exhaust system – adding force against the piston to slow it down.  

When an exhaust valve is closed substantial exhaust gases and back pressure are created. They eventually flow back into the combustion chamber against the movement of piston – causing pistons to slow down or stop moving entirely. Thus, creating the braking effect.

Exhaust brakes are known for their effectiveness and can provide a full stop braking of a fully-loaded vehicle even without applying the ordinary brakes – tough stuff.

exhaust brake

Exhaust brake has a valve that opens and closes. When closed, exhaust gases cannot pass through and this creates a backpressure that travels into the cylinder – resisting the movement of pistons.

Why Should You Use an Exhaust Brake?

Exhaust brakes should be used in instances where powerful braking is required. For instance, slowing down a fully loaded truck when downhill on a traffic. Or during an emergency where you absolutely need to stop the vehicle. 

So, only use your exhaust brake in a state of emergency. Yes, that’s right, there isn’t any reason for using this way of braking when you are not forced to. 

Wherever possible, you should use the regular disc brakes first. Exhaust brakes significantly slow down your diesel vehicle quickly. This means, you will need to use up more diesel (fuel) to re-accelerate and gain speed again.

Exhaust Brake Vs Engine Brakes Vs Jake Brakes

These three types of braking can be confused with one another but they work quite differently! Here’s the TLDR for now. I will cover each of them a bit more after. 

Exhaust brakes are used mainly by diesel engines, they compress the exhaust gasses into the manifold where they flow back and stop the movement of pistons. 

Exhaust brakes are usually used for big trucks where the brake discs alone are not powerful enough.

Which muffler is your car right now?

Engine Brakes on the other hand are the simplest solution for a gasoline engine. It works by removing your feet from the throttle while in gear. This closes the throttle body – preventing any more air to enter and thus slowing down the pistons.

Jake brakes – like exhaust brakes – work by operating with the exhaust valves. During a Jake brake, exhaust valves are opened prematurely to let pressure out of the cylinder. 

This means instead of letting the pressure push the pistons down, the pressure escapes into the exhaust system – removing the power source to move pistons and thus slowing down your vehicle.

Exhaust Brake

Exhaust brakes as we described, work simply by closing the exhaust valves in the manifolds with mechanical valves.

Instead of having the exhaust gases flow out into the exhaust system, they buildup and flow back into the cylinders – causing significant pressure that goes against the moving pistons and slowing it down.

They are very effective and simple to use in case of emergencies or when you need strong braking power. Unlike Jake brakes, exhaust brakes do not produce unpleasant sounds when applied – because of this they are fully legal in many countries.

 

Engine Brake

During engine braking, you let go of your foot from the gas paddle. This closes the throttle body and prevents any more air from entering. This actually creates significant pressure – which stops the pistons from pulling itself.

Imagine taking an empty syringe. Cover the syringe with your finger tip and try pulling the syringe. Did you manage to pull it down? Yeah, I don’t think so. Engine braking works exactly the same way. 

Engine brake is very simple and  can be applied in every combustion engine and it is one of the best ways to slow down when you are driving downhill. 

So, let’s give an example, you go down into third gear at 50 mph and you need to slowly come to a stop – what could you do in this situation?

You downshift into second gear and take your foot off from the gas pedal; the engine torque will help your vehicle to come to decelerate and eventually come to a stop. This way of breaking is very effective and doesn’t hurt your engine at all.

Plus, you are saving the brake pads from being used – which means less maintenance.

Jake Brakes 

During Jake braking, exhaust valves are opened prematurely during compression stroke to let the pressure out. This means there’s not enough pressure to push the pistons down for power – causing the vehicle to slow down. 

In the typical combustion scenario, combustion occurs when the piston moves up (AKA compression). During combustion, the explosion and exhaust gases create significant pressure that push the pistons down to move the vehicle.

On Jake brakes, exhaust valves are opened before the pistons complete their compression cycle (move up). This means when combustion happens, the created pressure goes directly out of the cylinder into the exhaust system – resulting in less power to move the pistons. 

These brakes were patented by Clessie Cummins in 1965 and the first company to make them was Jacobs Vehicle systems. And from this, they are known as the Jake Brake.

The biggest drawback of this solution is the sound these brakes are creating. In many countries, they are prohibited for use in city limits and they are used mostly on the highway. If someone is using these brakes where he shouldn’t, fines are very high.

 

Here’s a great YouTube video explaining the difference between exhaust brake, engine brake and Jake brakes.

Conclusion

If you are a truck driver and you haul a lot of things with your truck, an exhaust brake is a must in order to quickly and powerfully slow down your truck.

Exhaust brakes can even ensure your safety when you require immediate halt. So, use your exhaust brake wisely and stay safe on the road!

Ifandi S.

Ifandi S.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.

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