When dealing with horsepower and torque, every system on your car relies on the exhaust system to work efficiently. It doesn’t matter how much you increase air flow or fuel delivery if you aren’t getting rid of exhaust gasses quickly enough; all those other upgrades will be for naught. Performance exhausts are a crucial first step when it comes to upgrading your vehicle.
Exhaust Systems
Your vehicle’s exhaust system works in two ways. It removes exhaust gasses from your engine whilst simultaneously creating back pressure to encourage the removal of those gasses. These two processes work hand in hand to keep your vehicle running smoothly and efficiently.
Improving these processes has a positive impact on your vehicle’s overall performance by increasing horsepower and torque.
Where is the best place to start, though? First, you need to understand how your exhaust system works.
There are three main components to each exhaust system, with some vehicles having pipes to connect these components together. They are the headers, catalytic converter, and muffler.
Before diving into the different components, the first thing to understand is the exhaust pipe diameter. In some vehicles like the Subaru BRZ, the pipes are narrow and have outrageous bends in order to navigate through small spaces within the engine bay. This type of design is detrimental to exhaust gas flow and actually limits horsepower.
So, increasing pipe diameter is a plus. However, increase it too much, and you reduce back pressure, which in turn reduces your engine’s performance.
The general rule of thumb when upgrading your exhaust is to increase the diameter by ½”. There are some other factors to consider, such as the type of engine (naturally aspirated, turbocharged, or electronic fuel injection, to name a few), cubic inch displacement, horsepower output, and whether your vehicle has a single or dual exhaust system. But without getting into all those factors, increasing the diameter by ½” is a good place to start.
Now let’s look at the first component of the performance exhaust system – the headers.
Headers
This is the part of your exhaust system the exhaust gases first enter when leaving the engine.
From the factory, your car most likely will have come with a cast exhaust manifold made from either iron, stainless steel, or aluminum. The main drawback to cast manifolds is their inherent design creates excessive backpressure by gathering all the exhaust gasses together before they exit the manifold to the turbo or downpipe, depending on the vehicle.
Now, some backpressure is necessary, but manifolds increase it too much, whilst headers create just the right amount through the use of individual tubes leading to collectors.
Manifolds are also quite rough on the inside as they are created through a casting process, whereas header tubing is smooth on the inside, allowing for a faster flow of exhaust gases.
Catalytic Converters
The second main component of the exhaust system is the catalytic converter. Some vehicles will have multiple converters, but all vehicles manufactured after 1986 will have at least one as they are mandated by law.
This component reduces emissions emitted by the vehicle at the same time; it also reduces the exhaust gas flow rate. This is usually one of the first components replaced when upgrading to a performance exhaust.
In some instances, a converter is contained within the manifold and can only be replaced by utilizing headers. In this case, the vehicle will have a secondary cat further back in the exhaust system.
This one is easily replaced. It comes as a section of exhaust, including the cat sandwiched between two pipes. This section of the exhaust is in the middle of the system.
Again, the pipe diameter is important and should be increased by ½”. Since it is illegal to remove the cat, the next best option is to buy this component with a high-flow cat. This type of cat uses catalysts designed to maximize flow whilst still removing carbon monoxide and nitrogen oxide.
The Muffler
The last component of the exhaust system is the muffler.
The muffler can, in some cases, be replaced individually, but often it is replaced with the pipes leading toward the catalytic converter in what is referred to as a cat-back performance exhaust.
The cat-back exhaust component is responsible for the sound and tone of the car. I’m sure you’ve heard those ‘boy racer’ cars cruising down the street with an exhaust that sounds like someone loudly passing gas with their fart-can mufflers.
That’s not the cat-back exhaust system being discussed here. A proper cat-back exhaust will have a muffler, or two, depending on if it’s single or dual exhaust, that has been finely tuned to create an enjoyable sound whilst you’re cruising down the road.
Not only that, but it will also have a larger-than-stock pipe diameter to increase exhaust gas flow. So not only will you sound good, but you’ll also have the increased horsepower to go along with your new awesome-sounding performance exhaust.
All this to say, there are a few different options when it comes to upgrading your stock exhaust system to a higher-performance one.
Upgrading Your Exhaust System
The first decision is which components you are going to replace and in what order.
It’s best to start furthest from the engine. This way, your exhaust tubing will increase in size as the exhaust gas flows through it. If you start at the front, you’ll end up going from larger tubing to smaller, which will create driveability and power problems.
Now you know the order, let’s look at the three types of performance exhausts and the components they replace.
A cat-back system is from the catalytic converter to the tip of the muffler.
A turbo-back system will go from the turbo (if your vehicle has one or from the manifold if it doesn’t) back to the tip of the muffler and replace the cat.
And lastly, an engine back system encompasses the entire exhaust system.
So, figure out what your budget will allow and go buy your vehicle a new performance exhaust system. It will thank you.