Trends come and go in the automotive industry, but one thing that has always been cool is flames. Sometimes shooting flames is completely unavoidable and sometimes flames are purposely created on deceleration for show, either way, flames are cool. When you combine flames with an awesome sounding exhaust, you have a winning combination. Check out this video below from Topracing Garage. It features their customer’s GTR with a Topracing Garage tune and an Armytrix exhaust. The result is a lot of noise and a lot of flames!
As an enthusiast, you probably know that an aftermarket exhaust will add power to your car, or at least that’s what the internet says. The idea is that with a less restrictive exhaust your car gains power. What confuses many people is why a less restrictive exhaust gains power. Things like thermal efficiency, scavenging, velocity, and total flow all matter and can separate a great exhaust from a bad one. In this short article, we’re going to dive in-depth on everything you need to know about Armytrix exhaust systems and how they increase power.
As you probably know, exhaust gases are a byproduct of combustion. After the engine goes through the intake, compression, and ignition cycles, it now has hot gases it needs to expel to continue the cycle. The exhaust valve opens, and the piston comes up, forcing the air out of the engine and into the exhaust system. The purpose of the exhaust system is to route these potentially harmful gasses away from the cab of the vehicle and to the rear or sides.
Bigger is Always Better, Right?
Once the exhaust gases are forced out of the cylinder, they flow through the exhaust ports of the cylinder head(s) to the exhaust header(s). The gases come out in pulses, and if the headers are correctly designed, the low-pressure zone behind the pulse can help pull the next pulse along at a faster rate. This is known as scavenging and is one of the critical components to an aftermarket exhaust making more power compared to the stock exhaust.
After the header(s) is the rest of the exhaust system, which is typically comprised of a catalytic converter, mufflers, and resonators. In turbocharged cars, the exhaust gases flow through the exhaust housing of the turbocharger, then exit through a downpipe which mates up to the rest of the system. Depending on the size of your engine, how much power you’re trying to make, and a variety of other factors, the size of the piping will effect exhaust flow. The general idea is that a larger diameter is always better, but the law of diminishing returns applies; for example, a 5” exhaust on a four-cylinder engine is unlikely to make a difference in power compared to a 3” exhaust.
Heat is Energy
In case you didn’t know, heat is energy. As exhaust gas cools, its velocity decreases. Harnessing this energy isn’t extremely important for a naturally aspirated vehicle, but it’s important for turbocharged vehicles. With hot, high-velocity exhaust gases entering the turbocharger, the turbine can be spun faster resulting in better spool times, more power, and ultimately much better thermal efficiency. You can harness even more of the energy by using an exhaust wrap which is designed to keep the heat inside the header instead of it dissipating to the air under your hood.
Back Pressure Myth
All over the internet are “experts” claiming that four-stroke engines need ‘x’ amount of back pressure to run properly. This is entirely false. You see, with less back pressure the gases can exit the cylinder faster, resisting the upwards force of the piston less, and allowing the engine to rotate easier and ultimately make more power. The reason so many internet “experts” claim that you need back pressure is that unless a huge amount of time is spent on research and development, creating an exhaust system with no back pressure, great scavenging, and a great sound is basically impossible.
In general, a well-designed exhaust system is designed with a focus on improving scavenging and back pressure is not as large of a concern. To put it simply, most performance exhaust systems have a small amount of back pressure, as tuning that absolutely nothing is borderline impossible unless you are just running some sort of open header system which will be incredibly loud and is not something you want for the street. The real gains are in improving scavenging as much as possible, with decreasing back pressure also being a factor to power improvement.
How we do it
In general, larger piping diameter means more power, but that does not mean all exhaust systems are created equal. Armytrix focuses on not only improving flow, scavenging, and decreasing back pressure, but also on fine-tuning the exhaust note and keeping the entire design lightweight. Not only will an Armytrix exhaust increase power, but it will also be lighter than the stock exhaust, and our Valvetronic system allows you to quickly and easily change the exhaust note on the fly.
As Porsche moves towards turbocharged engines across their lineup of vehicles, including their coveted 911, a lot of enthusiasts were worried that these new Porsches would sound terrible compared to the old naturally aspirated Porsches. Although there may be some people out there who refuse to think turbocharged engines sound good, most of us have accepted this new turbocharged sound from Porsche and have learned to love it. Straight from the factory, the Carrera sounds pretty good, but it’s on the quiet side. The problem with many aftermarket exhausts is finding a middle ground between the exhaust being too loud and too quiet. This is where the Armytrix Valvetronic exhaust comes in, which allows you to change the volume on the fly.
Our Valvetronic system works by using a valve to direct the exhaust gases through a muffler or to bypass the muffler. With the valves closed, your Carrera with still be relatively quiet, but with the valves opened it turns in an absolute monster. On top of the awesome sound under loud, while engine braking these new Carrera’s love to pop and spit flames. Check out the quick dyno run below showing off this exhaust!
As an Armytrix fan, customer, or potential customer, you have likely heard of Valvetronic. It’s one of the prominent selling features of Armytrix exhaust systems and has shifted the entire exhaust industry towards adopting similar technology in all exhaust systems. The whole point of the Valvetronic system is to give you an option for how loud you want your car to be. If you leave early in the morning for work, you probably don’t want your car to be excessively loud, as it will upset your neighbors. Once you’re out on the open road or shredding a canyon road, you want to hear those awesome noises your car makes.
The Valvetronic system allows you to switch between being quiet and being loud with the push of a button via the included remote or through the smartphone application; this works by tapping into a vacuum source on your engine and connecting it to the control module. When you press the button on the remote or smartphone application, you are communicating with the OBDII module via Bluetooth. This OBDII module tells the exhaust valve module to allow the engine vacuum to open or close the exhaust valve. You can also set the exhaust valve module to an automatic mode which will open/close the exhaust valve based on predetermined RPM range or throttle position.
Aside from getting a brutal sound with the Valvetronic system open, you can also gain power, especially if your car is turbocharged. Depending on the car, modifications, and tune you have, the valve being open will also the exhaust gas to flow more freely, as it does not have to pass through any muffler. If your vehicle is turbocharged, you may see a slight increase in boost pressure depending if you are running an open or closed boost cycle, resulting in more horsepower.
As time goes on, emissions restrictions are forcing automobile manufacturers to use smaller and more efficient engines. Cars that used to have six-cylinder engines now have turbocharged four-cylinder engines, with more and more consumers picking the smaller engine over the larger engine. A big concern that many enthusiasts have is how the smaller four-cylinder engine will sound when compared to the six-cylinder of the same car. This exact situation is affecting the BMW G30/G31 520i/530i.
Armytrix decided to show the world just how awesome the 520i and 530i sound with a proper exhaust system. Now that the development is completely finished up, this new Valvetronic exhaust system for the G30/G31 is available for purchase. One of the great things about the Valvetronic system found inside an Armytrix exhaust is the ability to change the volume of your exhaust on the fly. This is great if you don’t want to upset your neighbors, but want to let your exhaust sing out on the road.
Separate from the Valvetronix catback exhaust is a new high-performance downpipe. These are offered without a catalytic converter for maximum performance, but a cat simulator is included to keep your engine light from coming on. With increased horsepower, Valvetronic mufflers, and a lightweight construction, the new Armytrix exhaust is a perfect addition to your 520i/530i.