How Does A Performance Exhaust Increase Horsepower?

How Does A Performance Exhaust Increase Horsepower?

Lots of car enthusiasts love upgrading their performance exhaust system, even if it just means making minor changes for style points. This fascination with large and loud pipes can be traced back to early car culture – notably American ‘Hot Rod’ culture – but the connection between big pipes and big power is much weaker, thanks to modern engine technology.

Despite the prevalence of vehicles pre-optimised by the manufacturer, hundreds of car enthusiasts still obsess over performance exhaust systems for improved horsepower. But is modifying your exhaust system the best way to improve performance, and what kinds of gains will you see from these, often costly, mods?

1. Do exhausts increase horsepower?

The main benefit of aftermarket exhaust systems is that they allow exhaust gases to flow more freely, supposedly allowing your engine to run more efficiently. The underlying philosophy of these oversized pipes is that by reducing resistance to exhaust gases, your engine can take in more fresh air, allowing for more efficient combustion and enhanced power.

However, the horsepower gains that a performance exhaust system could provide are likely much lower than the benefits of a turbo-charger, for instance. While most people will agree that these modified exhausts can provide a lot of benefits, it’s very hard to predict the horsepower gains you’ll see from changing your exhausts since the results vary greatly between models and engine types, as larger engines stand to gain the most.

If you’re uncertain of how a modified exhaust system could improve your car’s performance, we recommend asking an expert to give you an estimate based on your car model and specs.

2. What does an exhaust do?

Exhaust systems are vital for getting rid of the waste products produced by your engine –  including carbon dioxide and pollutants – so that your engine can cycle in the fresh air and continue the combustion cycle that powers your car. Exhaust systems are made of exhaust headers (intakes connected to your engine), mufflers and catalytic converters connected by pipes leading away from the engine and cabin.

All these components work together to transport exhaust fumes away from the engine, muffle the noise produced and filter out toxins before releasing them into the air. Without an exhaust, you would either choke on exhaust fumes, or your engine would fail altogether, making a good exhaust system vital and a performance exhaust system even better.

3. How does the exhaust affect performance?

In an ideal system, your exhaust will quickly and efficiently get rid of any waste gases from your engine, allowing it to cycle in the fresh air, combust fuel and get on with powering your car. However, a less-than-ideal exhaust system can cause a variety of problems, including reduced fuel efficiency and damage to your engine parts over time.

Because modern engines are designed to be a ‘closed system’ with all waste products being sent out the exhaust, any restriction or problem with the exhausts can ‘choke’ your engine, with potentially disastrous results. For these reasons, we recommend you get your exhaust system checked regularly and consider upgrading to a performance exhaust system if you feel your existing one is slowing you down.

4. How much HP does a performance exhaust add?

Aftermarket exhausts usually have wider pipes and other features that improve airflow to enhance engine efficiency, but how do these improvements translate into horsepower? Unfortunately, there’s no simple answer to this question, as the results will vary between different car models, engine specifications, conditions and more.

Depending on your car, an aftermarket performance exhaust system could give you as much as 50 extra horsepower or as little as 2-3 HP. To learn more about the benefits of upgrading your exhaust system or get an estimate of the horsepower benefits one might give you, try asking an expert.

5. What is the best performance exhaust system?

There is a wide range of aftermarket exhaust systems available, and they are typically grouped into categories based on how extensive the modifications are. From simple swaps of your exhaust tips and muffler to reworking your whole exhaust system, the different types of exhaust system modifications are:


Axle-back exhaust modifications involve replacing all the exhaust components from the rear axle (which typically includes your muffler), making it one of the easiest forms of exhaust modifications. As the least extensive type of mod, an axle-back exhaust system offers limited results, but is affordable and simple to fit, minimising the risk of mechanical issues.


Replacing all the components rear of your catalytic converter is known as a cat-back exhaust mod and provides considerable benefits to your car’s performance, noise and style. As an intermediate exhaust mod, cat-back systems are a great balancing point between low cost and drastic mechanical changes.

Header back

So-called ‘header back’ exhaust modifications involve replacing every part of your exhaust system, from the header to the tailpipe. These forms of modifications are the most comprehensive – and costly – option available, providing dramatic improvements to airflow but requiring significant mechanical work.


We recommend an axle-back exhaust mod for people who are new to car modifications, as they are affordable, simple to install and unlikely to cause any mechanical complications. If you’re unsure of where, to begin with your exhaust or are sceptical of the horsepower gains, we recommend asking an expert at DKU Performance who specialise in creating all kinds of bespoke performance exhaust systems.