Aftermarket Exhausts: More Complicated Than You Might Think
If you’re anything like me, you probably enjoy powerful and sporty cars (especially of the big engine displacement or forced induction type), and you might even be thinking about upping the soundtrack of your drive with an upgraded exhaust.
We’ve all heard cars buzz by us with all sorts of exhaust systems (or lack thereof), and sometimes it’s just nothing but unenjoyable noise, like two beehives having a fight inside a coffee can, or grandpa’s flatulence after soft serve ice cream. Most common, cheap, ready-made exhaust systems are—to be frank—crap, and most of the cars you hear those on are crap, too (or are owned by those who have no idea or care what they’re slapping on their cars).
Exhaust systems are supposed to be more than some pipe and a round can with a little bit of sound deadening. The majority of car manufacturers put significant effort into R&D, desiring a specific sound (or lack thereof) from their exhausts via the use of various mufflers, resonators, equalizers, and flow dynamics. Different materials make different sounds. This is lost on many aftermarket exhaust companies since they’re trying to sell basic crap in mass quantity to the naïve. On the other hand, there are many companies who value style, design and quality materials, and who create quality products for your vehicle.
Why would you want an aftermarket exhaust anyway? It goes FAR beyond just a good soundtrack. Car companies have to make exhausts fit their vehicles so sometimes good dynamics are not top of the list. They have to fulfill emissions and noise requirements, among other requirements. Some low-quality products are made of crush bent metals, making them extremely restrictive. When exhaust is restricted, the engine has to work harder to expel used exhaust gases. Using a quality exhaust, perhaps with larger piping and fewer restrictions, you are freeing up that previously restrained power. Also, factory exhaust tends to be heavy, and when you get into the more exotic materials (like 304 stainless and titanium), you see fewer weight savings as well.
Again, why would you want an aftermarket exhaust? The answer is simple: more power, better sound, less weight AND better fuel economy. Yes, better fuel economy! It can, however, be a double-edged sword, because the engine doesn’t have to work as hard to make the same power, so you can be lighter on the long pedal, BUT the sound from the upgraded exhaust is usually so enjoyable that you’ll find yourself accelerating more than usual, so those fuel savings can go right out the window!
When picking your exhaust system for your vehicle education is important, so let’s review types of exhaust and materials used in them.
Cat-back exhausts vs. Axle-back exhausts vs. Full exhaust systems
Typically, there are two types of exhausts available: axle-back and cat-back.
Axle-back systems, which are usually a rear section only, are becoming rarer. Cat-back means an exhaust system from the rear-most catalytic converter to the exhaust tip. They usually bolt or slip onto the flange or outlet right behind the rear-most catalytic converter.
There are also full exhaust systems out there that replace the factory catalytic converters or delete them entirely, but they’re not frequently used on street cars because they tend to be uncomfortably loud and require more extensive additional modifications such as engine tuning and you can pretty much guarantee your not going to pass your next emissions renewal. These racing-style exhausts are usually the ultimate in seeing power gains, especially on turbocharged vehicles as they usually involve new turbo downpipes as well and you will not only gain power you will also see less turbo lag. When NOTHING matters except maximum power and performance this is your best choice.
Types of exhaust materials used in MOST aftermarket exhaust systems
Let’s start with the most common: 409 stainless steel, used by many major exhaust manufacturers.
If you’re thinking to yourself, “Stainless steel is good stuff! It doesn’t mark or stain!” then all I can tell you is that not all stainless is created equal. 409 can degrade and deteriorate just like mild steel can. 409 is common and cheap to make, so it is the choice for many budget exhaust systems. Its lifespan is probably much shorter than you would think. If you live in an area with variable weather, frequent grime and grit, or even lots of salt, the lifespan will be significantly shortened.
409 lacks chromium and nickel, which provide much-needed corrosion resistance for something that is under your car and constantly exposed to high temperatures and the elements of nature.
304 stainless has a higher chromium and nickel content (around 20%, and 10% nickel), which makes it nearly impervious to rusting and corrosion. Additionally, the low ferrous content gives it an awesome gold color when exposed to heat over time. The weight difference between the two is negligible and depends on how thick the sidewall of material used is.
Top-end stainless steel exhausts are most commonly made from 304.
Stainless exhausts generally sound similar or identical to mild steel exhaust. The difference is that stainless systems are mandrel bent, which allows for better flow. Stainless exhausts are a great choice for cost-effective products, but you’ll need to ensure that you’re getting what is advertised. Some companies advertise their systems as 304 stainless, but only the muffler or tip is made from the advertised material. Many times, you will find that the resonators and the flanges are made of 409 instead of 304, as well. Read the fine print and ask questions if the manufacturer does not specify.
Titanium exhausts, on the other hand, have the best of everything going for them.
They’re corrosion-free, 40% lighter than stainless, and the sound is throaty and metallic. Titanium exhausts also tend to be works of art (Agency Power exhausts for example) because you cannot bend the material. Instead, bends are achieved by pie-slicing pipe and welding it back together again in sections to achieve the desired bend. Titanium also changes color with heat from blue to purple and bronze, and sometimes even green. Being significantly lighter, this is the choice of materials for cars where every bit of weight savings counts. This may not matter for your 4500-pound street car. Unfortunately, they’re more expensive, but if you want the very best of everything, it usually comes with a price tag. But the sound they make, like a freaking robot Pavarotti, will surely be intoxicating and rousing to almost anyone who has any appreciation for this type of thing
The sound of an exhaust depends on several factors: material types, muffler types, resonator lengths, flow restriction, and exhaust tuning.
The main factor in creating sound, however, starts in the engine.
No matter what, you will not be able to make a 4-cylinder sound like a Ferrari v12. You can, however, change the way it sounds with different combinations. Resonators in exhausts often look like catalytic converters but are actually free-flowing, straight-through mufflers packed with sound deadening. The longer the resonator is, the more effective it is.
The second thing to consider is muffler type. There is one universal truth when it comes to mufflers: the quieter it is, the more restrictive it is. Mufflers use a combination of baffling and sound-deadening materials to absorb and reduce sound, but the more of these baffles there are, the more restrictive the muffler is to exhaust flow. On a forced induction car typically the less restricted the exhaust is, the more power you will see but, the downside is the vehicle is going to be louder This is where your preference comes in: you have to choose your desired balance between sound and power. Keep in mind what you and any not so car loving passengers can tolerate on a daily basis. (Take it from my experience: it’s really hard to sneak home late at night when your car can be heard from four blocks away).
A newer trend is exhaust systems with built-in adjustability. These systems typically rely on adjustable valves and baffles, which changes the sound according to your settings. Most of these can be adjusted electronically on the fly, so when its time to drop gears and go, you can free up that power and unleash hell with the push of a button.
Applications are limited, and you can expect to pay a higher price than your typical exhaust system, but these systems are a great compromise when you want to stay undercover most of the time but be able to set off every car alarm in the parking garage when the mood strikes.
This author has a love for ARMYTRIX Valvetronic exhausts of this type for good looks and great sound, but there are MANY great companies such as ROUCH and Varex and others. This is not the same as an “electric cutout” tunable exhaust systems control flow changes internally to vary sound and exhaust flow with a switch or with a nifty remote and various modes.
It all comes down to the universal truth of the aftermarket world: you get what you pay for. This doesn’t mean you have to buy THE most expensive unit available for your vehicle. Different exhausts serve different purposes, and unless you have a car made in very limited numbers, you probably have a veritable cornucopia of options at your fingertips. Hopefully, with this knowledge in hand, you will be able to pick whatever is best for you, your budget, and other peoples hearing!