Can Aftermarket Exhausts Increase Motorcycle Horsepower?

One of the most popular modifications that bike owners make is adding a custom exhaust to their motorcycle. Trying to find a used motorcycle with a stock exhaust is like trying to find a used car with 100 miles on it. You’re going to have a hard time.

So why do people swap the exhaust on their motorcycle? Is it just so that it sounds better or louder? Or do aftermarket exhausts actually increase horsepower rideability of the motorcycle? These are all great questions that we’ll answer in this post.

What Are The Benefits of Aftermarket Exhausts?

The job of the exhaust is to provide an escape for the combustion gases from the engines cylinder. In a four stroke engine, the exhaust valves will open and then the piston will move upwards. This will push all of the fumes in the combustion chamber out through the exhaust. A properly tuned exhaust can help extract combustion fumes and seal in the new air fuel mixture that the engine sucks in. This can improve efficiency and power at specific engine speeds. It is a much more involved and beneficial modification than an exhaust wrap. In general, An aftermarket exhaust usually provides three things:

  • Less weight due to a lighter exhaust system
  • A louder and better sounding engine
  • Claims of increasing engine horsepower
  • Better looking exhaust system

Why Are Aftermarket Exhausts So Common?

An aftermarket exhaust is one of the easiest modifications yo can make to your motorcycle. It is literally a bolt on modification. Not only can the exhaust improve the aesthetics of your bike, but it can improve the rideability and sound of your motorcycle. Depending on what materials the exhaust is made of, it could be a significant reduction in weight.

Another reason why so many people modify there exhausts is because they are a cost effective modification to increase engine power. A slip-on exhaust can be had for several hundred dollars, while a full racing exhaust system like this one for a Kawasaki ZX10R can cost up to $2,000.

Slip On Vs Full System Exhaust

So what’s the difference between a slip on and a full exhaust system? A slip on or end can is the rear portion of the exhaust furthest from the engine while a full exhaust system covers everything from the engine’s exhaust valves all the way to the tip of the muffler.

An end can exhaust is cheaper and easier to install since you’re only replacing the end of the exhaust system. A slip on can provide an improvement in sound, and it will likely make the bike louder. The end can/slip on contains a muffler which can greatly improve your bikes sound. While a slip on can give your bike a deeper growl, it will provide little to no improvement in engine performance. A full exhaust system is what you need if you are looking for an improvement in horsepower.

How Much Horsepower Can A Full Exhaust System Add?

Motorcycle exhaust systems can provide a substantial improvement in engine performance. Aftermarket exhausts can improve horsepower by providing better airflow for the engine. The engine will have an easier time extracting spent combustion gases from the cylinder with an aftermarket muffler.

Since the aftermarket gases can leave faster, it allows more fresh air from the intake to get sucked into the combustion chamber. This improves the amount of fresh oxygen that is in the cylinder and allows the fuel to burn more efficiently.

A typical aftermarket exhaust can improve power by 7-10hp on a sportbike! That’s a massive improvement considering 7-10hp is a nearly 5-8% increase in total engine power, and that this is done from a simple bolt on exhaust.

One of the big reasons why aftermarket exhausts can make so much more power is because stock exhausts are very restrictive. The stock exhausts are restrictive to meet strict noise requirements whereas almost any aftermarket exhaust will be much louder than stock. Stock motorcycles are required to operate under 84 dbs on the highway. Most aftermarket exhaust systems will exceed this. So if you do modify your bike be sure to make sure that your exhaust system is street legal.

A full exhaust system can dramatically change the dyno curve of your bike. Depending on your bike you may not see a huge increase in peak power, but your engine could make more hp and torque and lower rpms than before.

While the peak horsepower gain might not be impressive, the bike could have noticeably more power before redline. I’ve seen plenty of before and after dyno runs on Harley Davidsons that show big increases in power in the 2000-4000 rpm range but top out at a similar peak power as stock. In summary aftermarket exhausts can improve rideability of your motorcycle and give you an increase of 5-10hp.

Do Aftermarket Exhausts Save Weight?

Many after market exhausts like those made by Akrapovic can actually be 30-40% lighter than the stock exhaust! In other words a full exhaust system on a Ducati Panigale can save you approximately 10lbs. Which is significant for a racing motorcycle. A lot of this weight savings comes from the fact that the exhaust is made from titanium. The benefit of the Akrapovic exhaust is that you don’t have to remap your fuel system when you install it. Other brands my require remapping. So that is definitely something you should be aware of when shopping for a new exhaust.

Conclusion

An aftermarket exhaust is one of the best modifications you can make to your motorcycle. It can improve the overall rideability of your bike and increase peak power by 5-10hp depending on the bike and exhaust system. Not only will it help your bike make more power, it can also reduce the weight of your motorcycle. Titanium exhausts can take more than 10lbs off of your motorcycles weight. Since this mod makes more power, makes your bike weigh less, sound better and sometimes even look better, an aftermarket exhaust is one of the best modifications you can do to your bike!