How Hot Does A Car Exhaust Get?

How Hot Does A Car Exhaust Get?

By knowing the temperature range the exhaust pipes should normally be at makes it easier for the motorist to identify any unusual temperature rise or decline from your vehicles exhaust system.

The vehicles combustion chamber produces waste, toxic gases. The exhaust system brings these combustion gases away from the engine out to an exit point. These fumes need to be cooled down, as they are very hot, and purified. The exhaust pipes are probably the hottest part of your vehicle. Very powerful cars can make the exhaust manifold glow in the engine compartment.

Follow this article to learn about how hot a car exhaust and exhaust pipe can get and the factors that determine these temperatures:

Exhaust Pipe Or Muffler Temperatures – Circa 1000F

The average temperature range for the exhaust system is between 600 to 930 Fahrenheit. Driving for a longer period or driving the car harder can cause temperatures to rise to 1600 to 1800 Fahrenheit as well.

The exhaust system is made up of many parts. This means that the temperatures will vary at different parts of the exhaust pipe. Around the catalytic converter and bends in the exhaust pipe right next to the cylinder are the hottest parts in the exhaust system.

Mufflers – 1200F

Hot combustion gases from the engine enters the muffler. The muffler dissipates powerful sound waves from within the fumes that goes through the exhaust. As a result, the muffler reaches a temperature of 1200 Fahrenheit whilst the engine is active. The higher the RPM, the higher the temperature in the muffler.

The temperature can also rise due to inefficient combustion of gases.

Catalytic Converters – 1400F

The catalytic converters remove any harmful emissions that are present in the exhaust gases. They will often reach a temperature of 1400 Fahrenheit. However, if unburnt gases from the combustion chamber pass through the catalytic converter then the temperature will increase significantly.

Oxygen or Lambda Sensor

The oxygen sensor is actually one of the hottest points in the exhaust system. The sensor measures the percentage of oxygen present in the exhaust gases, forwards this information to the engine management system or ECU and then adjusts the air-fuel mixture accordingly.

The sensor comes after (and before in some vehicles) the catalytic converter and deals with extremely high temperatures, so hot that it sometimes glows white in some vehicles.

How Does A Car Exhaust System Work?

Before we determine what makes the components in a car exhaust reach extreme temperatures, we need to understand how the exhaust system works.

What are the main functions of an Exhaust? To reduce noise levels, remove exhaust fumes, to improve fuel consumption and improve performance of the engine.

The exhaust system contains these elements: Exhaust manifold, resonator, catalytic converter, oxygen or lambda sensor, muffler, exhaust pipe and tail pipe. Depending on the make of your vehicle, the layout of the system can differ.

Let’s start from the exhaust manifold. Here, the toxic gases from the combustion chamber are collected from the cylinder head and are directed away from the engine into the exhaust pipe. Now, the gases are at very high temperatures, and due to the exhaust manifold being made of cast iron, it can withstand these hot fumes.

There are usually 3 or 4 cylinders that help remove the gases and then release through a single cylinder – called the front pipe.

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In modern vehicles, the exhaust gases will reach a first oxygen sensor. The oxygen sensor measures the amount of oxygen in the exhaust gas, sends this information to the ECU, the computer then uses that information to determine how much fuel is injected into the engine.

Next, the exhaust gases containing hydrogen monoxide and carbon monoxide go through the catalytic converter where they are converted into inert, less harmful gases. After this, the gases will pass through a second oxygen sensor and this will compare the amount of oxygen to the first oxygen sensor, making sure the catalytic converter is working.

The newly converted gases then pass through the resonator. The resonator changes and slightly mutes the sounds coming from the engine. It creates a more pleasant sound before it reaches the muffler without decreasing the power generated from the engine.

The muffler shapes and reduces the amount of noise coming off the vehicle produced by the exhaust. To cancel the noise of these sound waves, they are sent through a number of different sized chambers where the sound waves collide with the walls and are destroyed due to friction.

Finally, the exhaust gases consisting of less harmful gases along with considerably low sound waves move out of the tail pipe and into the atmosphere.

How Hot Can A Car Exhaust Pipe Actually Get?

Now that we have established the typical temperatures of the different components within the exhaust system, we can determine which different factors can cause the temperature to fluctuate in the exhaust pipe.

Condition Of The Exhaust System

The overall condition of the exhaust system must be satisfactory as it will determine the various temperatures that you will get in the pipe. The exhaust system must always be in a good state for maximum efficiency of fuel emission.

Abnormal high temperatures can be reached if there are many bends or constrictions on your exhaust system. This is because hot exhaust fumes are not allowed to escape easily.

Engine Speed

Of course, the combustion gases come from the engine. So, the faster the vehicle is moving, the faster the engine is working which means the exhaust valve sends more burnt gases with high temperatures heating up the exhaust pipe each time.

If the engine is at 2,000 RPM or more whilst driving, the temperature of the exhaust gases can significantly rise to 1100 Fahrenheit or even more resulting in a hotter exhaust pipe. However, if the engine is at 700RPM or less, the temperature of the exhaust gas will be 660 Fahrenheit or even less, which will result in a cooler exhaust pipe.

The higher the RPM, the hotter the exhaust pipe.

Tailpipe Length

The tailpipe has the job of taking the exhaust gases from the final silencer to the rear of the vehicle into the atmosphere.

The length of the tailpipe can determine how hot or cool the exhaust pipe stays whilst the vehicle is stationary or moving.

The longer the hot exhaust gases have to travel, the more heat will be lost before exiting the vehicle. On the other hand, the shorter the distance, it is more likely the gases will be warmer and thus, have a hotter exhaust pipe.

Having a longer tailpipe in some cases is more beneficial for the exhaust system as the exhaust pipes will be cooler rather than shorter ones.

Condition Of The Engine

To figure out if your engine is in optimum condition, the performance of the vehicle should be good, and it should be generating the right amount of heat within the exhaust gases. The engine will be consuming the maximum amount of fuel and producing the most amount of horsepower. Thus, temperatures naturally increase as RPM increases.

A faulty or older engine with technical issues will not perform well, which may result in overheating.

If the exhaust system is picking up combustion gases with higher temperatures than normal, the exhaust pipes will get hotter and will also under perform.

Tips On How To Prevent Damage To Components In The Exhaust

The temperatures of the exhaust system and exhaust pipes are very high, so the components around the exhaust are also at risk from being damaged.

Here are a few ways you can take precautions to avoid this:

Insulate The Exhaust Pipe

This is a very effective away of keeping the heat inside and preventing any heat to escape to other parts of the vehicle around the exhaust.

Although the heat is prevented from escaping, this doesn’t deter the performance of the exhaust system.

Exhaust wraps or tapes are wrapped in a spiral pattern around the exhaust pipe or manifold to insulate the pipes. Silica, fibreglass, basalt and ceramic are materials you can use for exhaust wraps which can withstand higher temperatures. Fibreglass starts melting at 1500 Fahrenheit.

These have been proven effective as tests have shown that exhaust wraps made of such materials can decrease engine bay temperatures by as much as 50%.

Use A Reflective Barrier Between The Engine bay and Exhaust Pipe

Sometimes preventing heat to space from the exhaust pipe can be difficult. In contrast, you can reflect the heat away from the engine bay and other components around it.

The heat can be reflected using a reflective barrier or material that stands between the engine bay and the exhaust pipe.

Heat control has been manifested in latest car models as car manufacturers have created embossed heat shields made from aluminium or steel. These shields are places 1-2cm away from the exhaust and exhaust manifold and this makes an air gap which helps to get rid of excess heat.

How To Insulate Components Around The Exhaust

Instead of insulating the exhaust directly, you can protect the components surrounding the exhaust. This, in relation to insulating the exhaust, will be easier and will not require an insulation without allowing excess heat through.

Components such as cables, wiring, hoses and hard lines that are near the exhaust can be insulated with heat sleeves. They reduce heat damage and are used in many new car engine bays.  The heat sleeves are typically made of aluminium foil and a backing of insulating fibreglass. The purpose of the reflective aluminium foil is that it repels heat that radiates from the exhaust.

A mylar foil outer layer is another popular material for heat sleeves. Mylar consists of a microscopic layer of foil laminated to an outside layer of polyester resin with insulating fibreglass backing. This polyester outer layer makes the Mylar very tough but can burn off at 400 Fahrenheit.

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However, with an additional, thicker outer layer of aluminium foil and insulating fibreglass, the heat sleeve is able insulate firewalls, motors or other components and can withstand higher temperatures, up to 1220 Fahrenheit.

What About Using Air?

When air is trapped in small pockets, it acts as a great insulator. Think about how double-glazing works.

In styrene foam and ceiling insulating batts, they trap air pockets and reduce heat conduction. As a result, like exhaust wraps and heat sleeves, the heat can’t be transferred through the material and acts a heat block. It is the air that is trapped between the fibres that reduces heat conduction.

How To Identify A Faulty Exhaust

A faulty exhaust can be identified through many signs and symptoms. If your exhaust pipe is hotter or cooler than the typical temperature it should be, then the driver can suspect that there must be an issue in the exhaust system or with the condition of the engine.

If you are experiencing any of the problems with your exhaust system listed below, then it must not be avoided and you need take immediate action.

Why is my Exhaust System making weird noises?

One of the obvious signs of a faulty exhaust system is the sound it makes. Different sounds reflect a different component of the exhaust system that is damaged.

If your exhaust makes a loud roaring noise, then check the muffler. Due to the muffler being the furthest away from the engine and condenses corrosive acids, the muffler risks of being corroded, allowing gases to escape and as a result makes this noise.

A chugging noise means that there could be a blockage in the exhaust system.

If there is a crack in the exhaust system, exhaust pipe or a leaking gasket, then this will result in a hissing or whooshing noise.

An exhaust system that has shifted out of place or is misaligned can create a rattling sound coming from under the vehicle.

Brackets and Hangers keep exhaust systems in place and provide support to the exhaust housing. If a support bracket, clamp or mounting has loosened then a loud metallic vibration will be produced. Something touching the exhaust pipe will also make this same sound. If any of the support elements become fractured, corroded or fall off then this can cause premature exhaust failure as the exhaust housing is not secure.

A Low Fuel Efficiency

A vehicle with an exhaust problem will consume more fuel than usual. This occurs when the Exhaust Emission Control Device is not working properly. The engine must work even harder to compensate for this and as a result drains the fuel to keep the vehicle moving.

To avoid this increase in fuel expenses check the entire exhaust system to get this problem fixed as soon as possible.

Fumes Leaking Into The Car

Many toxic gases are driven away from the engine, through the exhaust system and out of the tailpipe into the atmosphere. If, however, the fumes can be detected from the vehicle through smell, then there is something wrong with your exhaust.

Exposure to gases such as carbon monoxide can be very harmful when inhaled, causing drowsiness to passengers within the vehicle. In addition, a leaking exhaust pipe will also result in the smell of gas entering the cabin. Do not drive the car if this is the case.

Condensed Exhaust Pipes

Toxic gases are directed away from the engine to be converted into water and carbon dioxide in the catalytic chamber. However, if the water is not able to escape, tiny holes causing leaks and rust can form as a result of condensation in the muffler.

Condensed, leaking exhaust pipes should be regarded as hazardous and the entire exhaust system needs to be checked immediately.

Visual Check

Getting to know how a good and efficient exhaust system looks like is crucial to identifying any physical damage. An exhaust pipe that is out of place, dragging or hanging is abnormal. This can cause leaks in the pipe, and unattractive sounds. Hanging exhaust pipes can rip off at any time and cause damage to other vehicles and motorists.

When driving off-road or over potholes, the jolt of this on the vehicle can cause loss of parts on the exhaust system. Therefore, it is important to visually check the entire exhaust system for any irregularities and getting it fixed or replaced.

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Rusting

Another problem that can be identified through a visual check in rusting.

Rust is formed as a result when water comes into contact with the exhaust and combines with combustion gases, leading to corrosion of the system. Often, in the muffler, if the gases are not hot enough to vaporise, then internal condensation occurs because of water depositing which causes rusting inside the muffler. Environments that experience high snow and rainfall present rusting problems in cars more commonly.

Using your vehicle for short trips will lead to more corrosion in the exhaust system than longer distanced journeys.

If rust is found on the surface of on any of the components in the exhaust system, it may not look serious. The rust could possibly go through the components surface or be rusted from inside.

If one component is corroded, it is likely that other parts that were installed at the same time will corrode as well. In some situations, different components of the exhaust can actually merge together due to the heat build-up and will also be corroded together. Thus, separating these parts is extremely difficult.

By using a screwdriver, you can gently scrape the rust to see if any of the surfaces gave weakened. If a hole is formed easily then that components needs to be replaced.

Low Power and Acceleration

The exhaust system is connected to the engine. So, if the exhaust is underperforming, such as combustion gases overheating the system, then the engine will have to work harder. This will result in a reduction in power and acceleration from the engine.

Catalytic Converters

We know the typical temperature a catalytic converter should be. So, what damage can extreme temperatures do to the catalytic chamber?

Extremely high temperatures as a result of unburnt gases in the exhaust can cause damage to the fine catalyst material. As less chemical conversions take place, the catalytic converter becomes less effective and there is a decrease in engine performance. This is dangerous for the environment as there are now more harmful gases being expelled from the exhaust.

On the other hand, when the catalytic converter reaches cooler temperatures, this also poses issues. For example, if the chamber is submerged in water, the internal honeycomb structure can pull apart, meaning the exit to the exhaust pipe will be blocked. This will decrease engine efficiency and engine power.

Exhaust Systems and the Law

If your vehicle’s exhaust system is producing excessive amounts of exhaust gases, then a police officer has a right to warrant the removal of the vehicle from the road. In addition, if the exhaust system is too noisy and is broken, then your vehicle can come under scrutiny by the police. Incorrect emissions coming from the exhaust system can be identified in your MOT test and will fail until the fault is resolved.

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