Car Exhaust Systems: The In and Outs

When governments and certain groups complain of polluting car emissions, they usually talk about how cars have inefficient engines and exhaust systems which pollute harmful greenhouse gasses into the atmosphere. However, we aren’t here to talk about messy policies and subjective opinions but rather the way in which a car exhaust system works. We will firstly touch upon the cars intake in order to get a sense of the bigger picture and how the pieces all fit together.

McLaren 720S at HK Disneyland Car ParkThe McLaren 720S next to the legendary Ferrari F40 Hong Kong

Quite similarly to how we humans breathe, cars have to breathe too in order to produce useful energy. The air which they breathe is mixed in a combustion chamber with petrol and a spark to move the pistons and ultimately the engine. They breathe using what are called car exhaust systems which involve an intake to bring the oxygen in and an exhaust system to expel the used oxygen out.

Intake

Porsche 996 Turbo IntakeThe Porsche 996 has it’s intake vents on the sides due to the rear positioning of the engine

Intakes: the nose and lungs of the vehicle. This is where the magic starts. The intake, as it implies is what provides the air into the engine. Whether or not force induction is involved (which we will leave for another chapter), depends greatly on the vehicle however assuming it does not have one, an intake roughly comprises of the following components:

  • Air filter
  • Tubes
  • Intake manifold

Each of them have a significant purpose: The air filter cleans out any harmful particles to it’s best ability so that the oxygen is as pure and clean as possible (leading to more power and efficiency). The tubing connects the air filter to the intake manifold and acts as a “tunnel”. The intake manifold is then the system which equally divides the air up so all the cylinders get exactly the same amount of air. This air then goes into the engine and the combustion process begins.

Forced induction vehicles will usually have a turbocharger after the air filter to increase pressure and an intercooler to cool down the air to make it more dense.

Exhaust manifold: how exhausting…

2JZ-GTE Exhaust ManifoldAftermarket Exhaust Manifold meant for a 2JZ-GTE engine found usually in a Toyota Supra

After the whole internal combustion process (which you can read upon in one of my articles here), the engine now has to exhaust of the gasses produced, just like our bodies. This is done through the exhaust system which I’ll get into right away. Exhaust systems are not only a way to exhaust gas but expel it in a more efficient manner than without one.

The harmful carbon dioxide and residual gasses are exhausted through what’s called an exhaust manifold which is structured similarly to an intake manifold, just it does the opposite function. The exhaust manifold connects to all the exhaust ports with the help of flanges which make a very tight seal so no exhaust gasses can escape in the process. Gaskets are put in between each connection to ensure that this seal is as tight as can be. The exhausts than continue to the catalytic converter with the help of piping.

Catalytic Converter: What does a cat have to do with car?

Exhaust systemsThe catalytic converter reduces emissions and helps stabilize the hot fumes coming from the engine

The catalytic converter serves one major purpose and what policymakers are always concerned about, reducing emissions. Catalytic converters (along with the other few components) already do a good job by reducing almost 90% of harmful toxins which otherwise would have been directly exhausted into the atmosphere.

The catalytic converter, otherwise known as “Cat” for short, reduces the following toxins:

  • Carbon Monoxide (CO)
  • Nitrogen Oxide (NO)
  • Hydrocarbons

This is all done whilst affecting the air flow as little as possible and cooling the gas significantly.

Muffler and Resonator: Quiet or Loud?

Muffler on a 1967 Ford MustangExhaust system with a muffler on the 1967 Ford Mustang

The muffler and resonator are powerful and quite smart components of the exhaust system which aims to muffle and silence most of the sound coming from the engine without completely constricting air flow. It does so by creating a chamber in which the sound waves crash into each other using physics in order to almost cancel each other out. All while keeping the air flowing through the system without any constraints.

The resonator is another integral component which sometimes even replaces the muffler due to how effective it can be. Resonators function fundamentally the same but rather focus on a certain frequency range of the sound waves coming from the engine. Due to it’s limited frequency range cancellation, a resonator could work particularly well on a diesel vehicle due to it’s limited/smaller rpm range and thus smaller frequency range leading to a larger portion of the frequencies being cancelled out. In most vehicles, mufflers and resonators come as a standard. Funny enough, resonators can also be tuned to make the exhaust note louder for more exotic sports cars.

A hybrid between the two often exists: a muffled-resonator or a resonated-muffler which has the features and benefits of each component.

Tailpipe

Now for the part that is actually visible! Of course, the tailpipe! Now before I get into the actual technicalities of the tailpipe – you might have noticed that some tailpipes/exhaust tips on modern cars are fake and look detached from the entire exhaust system. In some cases that is true and is only due to aesthetic purposes. For example on the Mercedes C-class, the exhaust tips are clearly fake and are even blocked, leading to the actual ugly exhaust pipe peeping out from the bottom. Another culprit is the Audi RS6 seen below:

RS6 TailpipeAudi RS6 seen with a fake exhaust tips to embellish the real exhaust pipes 

Which leads me straight into it’s function… it doesn’t really have one other than for pure aesthetics. Since it’s at the end of the exhaust system, as long as the exhaust pipe is big enough for the fumes to leave the vehicle efficiently then the exhaust tips are purely for designers to play around with. Some just found a loophole and added fake exhaust tips to it just to look good whereas other can actually do a great job of making it look good!

What can good exhaust systems actually do?

Exhaust Tip AMG GTGood exhaust systems lead to increased overall performance

What does having a good car exhaust system actually do, you may ask? Well there is a myriad of different implications and effects they might have but the most significant ones are the following:

  • Higher power output
  • Better Throttle Response
  • Improved Fuel Economy

The reason for such is that have a good exhaust system implies that the gasses are passing through the system efficiently making it a lot easier for the car to breathe. As such, the car can now intake in more air and exhaust more fumes than what would normally be possible. This results in higher power output, also a better throttle response due to the freer air flow and improved fuel economy as the oxygen is being combusted and exhausted more efficiently. 

Maintanence:

Car exhaust pipeExhaust systems will experience acidic moisture regardless of how well-maintaned they are 

Another tip to keep in mind is due to all the fumes going through the exhaust system, it will be bound to create acidic moisture as a byproduct which isn’t all that great for the pipes themselves which is why they need regular maintaining and possibly changing, even if they are well cared for.

All in all, exhaust systems are some very important components in a vehicle which help it breathe, produce power and ultimately expel the byproducts of combustion. Some are better than others, some have different purposes and functions but each one ultimately has the same fundamental purpose.

I hope you found this quick introduction to exhaust systems useful and if you have any personal experiences with changing any of them or buying any aftermarket exhausts to your car, then please comment them down below!

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