Exhaust modifications and upgrades are among the more popular ways for riders to spruce up their bikes. They're easy on the eyes and relatively easy to install, so that could explain why we see aftermarket exhausts on a lot of motorcycles these days. While it may look and sound good, does changing the exhaust affect bike performance? Several factors go into this, and we'll cover them in this article.
The stock exhaust that comes with your motorcycle was carefully designed to integrate with every part of the bike. While it may not bring out the maximum performance, it usually balances power with noise and emissions. If you want to eke out more power with little regard for the other stuff, then you could install an aftermarket exhaust on your motorcycle. Whether you pick up an aftermarket exhaust for your adventure bike, or your scooter, as long as there is an engine these rules apply.
The two types of motorcycle exhaust
There are generally two main types of exhaust systems available in the market, slip-on or full exhaust.
A slip-on muffler can be easily attached and removed from the motorcycle. This type of exhaust attaches to the stock system and replaces the muffler or tailpipe. While slip-on exhausts are usually cheaper than full systems, gains in performance are minimal. Installing a slip-on is great for changing the look and sound of a bike, but don't expect massive boosts in power. At the very least, increased throttle response is possible if the muffler produces less backpressure.
The second type is known as a full system exhaust. A full system replaces the stock header, mid-pipe, and muffler. Aftermarket full exhausts are typically made from lightweight metals, and when installed, can take some serious weight off your bike. Installing a full exhaust that flows well can also decrease engine load when expelling gases, which may increase efficiency. This option can bring noticeable performance gains, but it can also be significantly more complex.
Installing a full system exhaust
When installing a full system, procedures differ based on whether you have a carbureted bike or a fuel-injected motorcycle. This is because most aftermarket full exhausts require changes in fuel management to work at their best.
The goal of changing the fuel management system is to prevent the engine from running "lean," which, in this case, happens when more air is entering the cylinder, yet the amount of fuel per stroke remains the same.
When an engine runs lean, it tends to overheat quickly and may even backfire when the bike is decelerating. Needless to say, any hope of performance gains would be gone in this scenario.
The opposite of this is running "rich," in which the engine receives more fuel per stroke and not enough air. Stock exhausts do generally well at walking the line between performance and fuel economy, but full exhaust systems need an extra step to ensure optimal function.
This is where fuel system management comes in. If you have a carbureted bike, you will need to acquire a jet kit. A jet kit is a collection of parts that allow you to reconfigure a carburetor's fuel delivery. Installing a jet kit is usually straightforward, although it will take some time and effort.
On the other hand, fuel-injected motorcycles come equipped with engine control units (ECU) that determine the bike's air-to-fuel ratio automatically. In this case, you will need a fuel controller. A fuel controller intercepts the signal coming from the ECU and relays its own information to the fuel injectors. The result is an air-to-fuel ratio that's appropriate for your bike and the exhaust. Keep in mind that the fuel controller may need to be mapped with computer software, so consult with a professional for best results.
Some higher-end motorcycles are equipped with oxygen sensors that feed the correct data to the ECU. With an O2 sensor, you could do without a fuel controller, but we still recommend it.
The type of exhaust you should get
We've established that changing the exhaust can indeed affect a bike's performance. Whether you should go with a slip-on or full exhaust system depends entirely on yourself. If your goal is simply to change the look, feel, and sound of your bike, then perhaps a bolt-on exhaust will do the trick. They’re easy to install, come in a variety of looks, and usually won’t harm your engine.
If you want the performance boost that comes with less weight, reduced back pressure, and a reworked fuel system, then you could go with a full exhaust. By some accounts, power gains from a full exhaust system can reach up to 15%. However, achieving anything close to that number can only be possible with proper fuel system management. So, if you're considering an upgrade, make sure you get that jet kit or fuel controller along with your aftermarket exhaust to maximize your returns.
As always, choose original parts from established brands, and check with your motorcycle's manufacturer to find out if installing a slip-on or full exhaust system could void your warranty.