Aftermarket Exhaust Motorcycle
Aftermarket Exhaust Motorcycle – Perhaps the most common modification out there, a tuned exhaust system can boost your street cred. But what about performance gains? Here’s what you need to know.
Standard motorcycle exhaust systems are built to meet strict noise and emission standards. They channel toxic gases from the engine to the outside world and should be done in the least dangerous way possible. So they are limited, although much of the limitation can be focused on influencing power characteristics with headers and down pipes.
Aftermarket Exhaust Motorcycle
The exhaust system must remove gases as efficiently as possible for optimum intake. The better the flow of gases through the system, the larger the exhaust can scavenge, the greater the vacuum in the combustion chamber and the stronger the subsequent intake.
Cb400x / Cbr400r Modified Stock Exhaust
Pressure waves play a big role in optimizing the flow of gases. The sound of the exhaust gas being expelled from the exhaust valve creates a high pressure wave that travels down the pipe. When it reaches the open end, it reflects back down the pipe as a low pressure wave.
If the low pressure wave approaches the exhaust valve as it reopens, it improves engine efficiency and helps eliminate the aftercharge of gas. As the low pressure waves travel back up the pipe they become high pressure waves once again. If these reach the time the exhaust valve closes, they can force any fresh inlet charge back into the cylinder, which also improves engine efficiency.
The length of the header pipes determines where the pressure waves are located and they must take engine speed into account. The low pressure pulse that can reach the exhaust valve at 4,000rpm is only halfway there at 8,000rpm, so the low pressure waves arrive at the exhaust valves when you need higher pressure.
Other factors come into play; A larger pipe bore allows more gas to flow, thus increasing top end, while a smaller bore draws burnt gases from the cylinder faster to increase low-end power. Tapering of pipes also accelerates the flow. Structure also affects properties; The 4-1 system boosts the top end, while the 4-2-1 broadens the powerband.
Suzuki Gs550 Performance Exhaust Motorcycle Mufflers Flare Tip Chrome
Ultimately, the exhausts are designed for optimum power at low or high revs. Some manufacturers install electronically controlled valves in their exhaust systems to control the flow pressure waves at low revs without sacrificing too much top end. They’re usually lost with an aftermarket system, but since they only do their job up to about 4,000rpm or so, losing them doesn’t sacrifice as much drivability as you might think.
Race systems, on the other hand, work on the assumption that you want to sacrifice drivability for maximum power. Although it can add up to 15bhp in the higher rev ranges, the bike falls short below 8000rpm. Meanwhile, standard downpipes deliver more usable than ultimate power.
If the exhaust system is improved without a fueling remap, the engine may not be able to take in as much fuel, instead drawing in more air, diluting the mixture. However, clever design, taking advantage of the bike’s rich standard fueling setup optimized to meet emission norms means that some complete systems work well on standard bikes without any modifications.
A more popular and less radical modification is changing the end canister (slip-ons). A standard silencer directs the noisy gases back and forth through a series of energy-sapping chambers before quietly releasing them. By not maintaining noise levels, an aftermarket can allows gases to flow more directly, reducing the average gas pressure (back pressure) in the system so gases escape more easily.
How To Install An Aftermarket Exhaust
Results will vary depending on the bike’s standard setup, but as long as the canister is well designed the engine will produce more power even without a remap. An aftermarket can alone is usually not enough to run an engine dangerously lean.
A full race system gets you more power but at the expense of drivability, while an aftermarket finish puts out less power but without drastic effects on the powerband – or the absolute need for a remap.
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Recently I found, purchased and set out to install a new exhaust system on a 2018 Kawasaki Z900RS Cafe. The result I wanted with this project was twofold. First I wanted a system that would change the look of the bike. Second I wanted a bit more bite from its 948cc inline-four. Here’s how I went about it…
Aftermarket Exhaust Buying Guide
As I already mentioned I have 2 goals with my exhaust upgrade. The first is to get the look I’m after.
My Kawasaki Z900RS wore a cafe gray and black paint scheme and the silver colors on the bike seemed a little off-putting. I fixed most of them by painting them black or swapping them out for black alternatives, but the elephant in the room is definitely the exhaust system. I also want a muffler that looks like the aftermarket systems riders used to fit a Kawasaki Z1 in the seventies. Don’t get me wrong, Kawasaki did a fantastic job with the Z900RS exhaust. It’s not as “retro” as I would have liked.
My second goal was to increase the performance of the bike. I’m no hoon, but I know the Z900RS has more to offer and I want to taste it.
There are many ways to do this, but an exhaust upgrade will always give you the best bang for your buck. To make sure I get an exhaust that will definitely improve the bike’s performance, I searched for a brand that developed a system specifically for the Kawasaki Z900RS. After scouring the internet, Z900RS forums and reaching out to Facebook groups I came across Brock’s Performance website.
Custom Motorcycle Exhaust
Brocks Performance offers a range of performance-oriented parts and accessories for a wide range of motorcycles, including a variety of the latest modern classics. In the case of the Kawasaki Z900RS, they are selling a tailor-made system that was developed when the Z was first released. They call it StreetMeg.
Similar to the bike’s stock exhaust, Brock’s Performance Z900RS Streetmag 4-into-1 system. 4 header pipes merge below the engine and are distributed with the stock catalytic converter. Sitting at the end of the headers is a classic drag race style 20 inch ‘sidewinder’ megaphone muffler. And, as fate would have it, the Brocks Z900RS Streetmag also comes in a Black Cerakote finish.
Conveniently the StreetMeg exhaust bolts directly into the Z900RS using the factory mounts. It won’t interfere with any other components (like footpegs or hoses) and you won’t lose any corner clearance. The system also offers huge weight savings. The Z900RS Streetmag exhaust and all its hardware weighs just 10.9 pounds. That’s a massive 58% reduction compared to the bike’s stock setup.
As for performance, each Brock’s exhaust system is specifically designed with performance in mind, including the Streameg, but more on that later.
Dunex8 Tec 2 Into 1 Stainless Aftermarket Exhaust
For those who haven’t heard of Brock’s Performance, the company was started in 2002 by American drag racer Brock Davidson. Brock started building and racing motorcycles at the drag strip from a young age, but the year 2000 changed everything for him.
First, he and a group of his friends built a motorcycle to compete against Kawasaki’s own race team in the 2000 AMA ProStar Superbike Championship. Despite a huge difference in budget and some seemingly insurmountable odds, Brock took home the first place trophy. That same year he became the first racer to complete a 7-second quarter-mile pass on a street-legal motorcycle, riding a modified ’97 Suzuki Bandit 1200. Those 2 wins combined with extensive knowledge of motorcycle performance modifications gave Brock the confidence to start his own brand.
Brock’s performance catalog focuses on engine, driveline and chassis performance components. As well as selling their own products, they also stock many parts (filters, engine control modules, suspension parts, carbon wheels, etc.) from partner brands that complement their products. All components can be purchased individually, but Brock also offers complete performance packages to suit the needs of different riders.
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