Exhaustive Series #1: Exhaust 101--Da Parts

A Beginner's Guide to Everything Exhaust

Considering upgrading your Exhaust? A number of truck enthusiasts choose to start here and for good reason. You can improve everything from your horsepower to your fuel economy (well, sorta) by upgrading your Exhaust system. But first, it may be important to know what all these parts even do. If you've already got that covered, you are likely ready for Part 2 in this Series: Performance Exhaust Systems.

Getting to Know Your Exhaust

Before you actually start replacing parts, you should make sure you know a little about what each part does and why it is worth upgrading in the first place--as well as what you should expect once you get that aftermarket Turbo-Back Exhaust System installed. We'll have a quick look at each part to just give you a general understanding of each, for a general understanding you really should have before you start taking stuff apart--my shop teacher always said, anyway. Your Exhaust in a nutshell is the system that takes any gases that are a byproduct of your combustion engine and expel them from your vehicle out your tailpipe. But along the way, your stock system throws a lot of restrictions in the way that are both due to Federal regulations (like your catalytic converter or DPF) and designed to reduce sound (such as your muffler), which in the grand scheme of things clog the flow of said gases. All these restrictions actually build up something called backpressure, which cuts down on your overall horsepower and performance, and may even (say it ain't so) cause your engine to use some extra power to force your exhaust fumes through this intricate series of pipes and machinery. This may make you wonder if it is really all worth it. Ideally, at least in some enthusiasts' minds, your engine’s exhaust would be a system of pipes that cross each other at least once and end in two straight tailpipes. But it might all be a bit more complex than this. But before we decide what is ideal for your exhaust, let's just take a general trip along the piping to discuss the various parts of this vital system before you decide if you actually could go without that muffler (unadvisable).

Let's take this baby apart: one piece at a time!  

Headers or Exhaust Manifolds

The source of your exhaust river: your Headers (a.k.a. exhaust manifolds). These babies attach to your combustion chambers. You should have as many tubes coming off your head as you have cylinders. For instance, if you have an 8 cylinder, you'll have 4 tubes coming off each side (note that in our picture here we've only shown one side, so half of an 8 cylinder header). Each design is different, some merging more quickly into a single large pipe while others are more gradual. Length wise headers come in full-length and shorty. Which you choose will be up to your engine and how much room you've got to work with. Your headers are responsible for scavenging spent gases from your engine, which is a fancy way to say they guide the hot exhaust away from your cylinders, but good headers do this at such a rapid speed (do to a lack of restriction) that the gas flow actually creates a mini vacuum which pulls excess fumes from your engine--out of the next cylinder. This cuts down on backpressure, increasing performance right from the get go. This is why truly maximized exhaust systems start with your headers (also called Header-Back Aftermarket Exhausts). Your stock exhaust manifolds are likely made using "crush bends," whereas a good Aftermarket Header and Head Pipe will be made using Mandrel Bends. Cush bending is a cheap method of bending pipe that actually produces more friction within it--restricting airflow. Mandrel bending uses a flexible rod and prevents any kinking, keeping friction to a minimum, allowing maximum gas/air flow throughout your exhaust system. If you are shopping for an aftermarket exhaust, you want Mandrel Bends for all your piping.

UpPipe & Turbo (on Turbocharged Engines Only)

Next up after some Head Pipes will be your Turbocharger, if you have one. These marvels of machine goodness are actually composed of two little wind turbines (the one on the Air Intake side is actually called a compressor, but it's basically the same thing). As the hot air from your exhaust pushing past this turbine, it spins forcing the compressor side to turn because--yeah--they are mounted on the same shaft, thus sucking in more "cold" air into your intake: increasing horsepower by forcing more air into your cylinders, which in turn increases fuel consumption. These babies basically take wasted energy (your engine's hot exhaust fumes) and pump that energy (not the fumes) back into the system, conserving power. While most don't think of their turbocharger as being part of the exhaust system, it certainly is as it is connected to the head pipes by an UpPipe or sometimes even a Pre-catalytic converter. If you don't already have a Turbo and are considering re-doing your entire exhaust system, you should really consider including one in your plans. These bad boys increase horsepower and may even give you a jump in miles per gallon. Any aftermarket part that increases power and MPGs is alright in my book! Some studies even claim turbochargers cut down on air pollution.  Kinda a win-win, am I right?

Downpipe

Next up is your Downpipe. If you don't have a Turbocharger, this may be the first set of piping right after the head pipes which come off the headers (or right after the pre-catalytic converter). Technically the downpipe runs pretty much the rest of the exhaust system and is interrupted periodically by a number of additional components such as your muffler and catalytic converter (love 'em or hate 'em). Again, your stock downpipe is likely bent using a crush method, which means it is prone to kinks and produces more friction as the hot gases of your exhaust push through it--more restriction means less horsepower and more backpressure. Again if you are ordering an aftermarket downpipe it should be mandrel bent, so make sure it states that it is, as this eliminates most of the extra friction, creating a free flowing pipe. The other thing to consider in your downpipe is the diameter. Aftermarket downpipes tend to have a larger diameter than stock ones, increasing the volume and hence the air flow--once again cutting down on backpressure and increasing performance. I know it can be hard to believe that just changing pipe size can improve your vehicle's horsepower, but it is science, man! And it's true. You will need to make sure you get the proper diameter to mesh up with your manifold or hopefully new headers and to match your engine size. After all, there is no need to overdo it either. Maximizing your diameter is not just about ordering the widest pipe, but the right width for your ride. Going too big can actually cause the exhaust air to cool, slowing the flow. In general if your engine has 350 horsepower or less, your pipes should be 3 to 3 1/2 inches in diameter. If you're pushing out 400-550 horses, go with a 4 inch. More than 550? Time for a massive 5 inch!

DPF (Diesel Particulate Filter--on Diesel Only)

If you're rocking a diesel truck that was manufactured in or after 2007, guess what--you've got one of these. Here at Midwest Aftermarket we are all about being eco-friendly (don't get me wrong), but you (and we) likely think these @#$%ers kinda suck. But rules is rules, and we don't go around bucking Federal laws left and right nor would we ever tell you to attempt to do so yourself. But you also know our viewpoints on it being your truck and all, so I guess freedom and all that--do what you want. This article isn't about telling you how to remove one of these bad boys (for active cleaning only, of course), but rather to tell you what all the parts are and what they do and where they are located in your exhaust system. So let's get on that. Your DPF or Diesel Particulate Filter (along with its DOC component) will show up on your Downpipe next (though sometimes one of the two to three catalytic converters comes first). These filters are only on diesel vehicles from 2007 on, so if you are rocking a classic, you may not have one and should probably count yourself blessed. Since you can't (legally) remove these, I really have only included it here as a point to illustrate where your DPF-Back Exhaust System will start: here. Next up is the other Federal mandated piece of exhaust equipment that everyone has on their daily driver: the Cat.

Catalytic Converter

You may have two or three of these scattered along your Downpipe. It is illegal to remove your Catalytic converters (a.k.a. Cats) and we would never instruct you to do such a thing, though it is possible to purchase a replacement and modify your Cat with one that is less restrictive. And really that's the whole issue here. Again, we all like fresh air and both your DPF (if you're rocking a Diesel) and your Catalytic Converters help to keep harmful air pollutants from getting into your and my lungs. The problem is that they tend to be restrictive and hence increase backpressure, preventing maximum flow, and all of that terribadness that we've been talking about so far. Not only can you replace the stock Cat with a better aftermarket part, but you also need to know where this baby sits on your Downpipe because this is where any Cat-Back Exhaust System beings--after your FINAL Cat (not the first one and maybe not even the second if you've got three, so locate carefully).

For all you nerds out there, let's talk briefly about how these bad boys work. Typically there are two separate honeycombs of catalyst inside the Cat. One reacts with the nitrogen oxide (smog producing emission) breaking it down into nitrogen and oxygen. The other adds oxygen molecules to carbon monoxide (that nasty poison stuff) making CO2 and water. Much of the stuff the catalytic converter tackles cause cancer and produce dangerous fumes that lower our immediate air quality, so it's probably a good idea to have 1 or 2. Also, I once knew a guy who claimed he found God in one of these puppies, but I think he was on a long crazy road trip and stopped in Topeka late at night hopped up on Monster Energy.

Muffler

Nearing the end of our journey through the exhaust system, we find your muffler. These standard stock parts reduce exhaust noise or muffle it. Pretty clever name, right? Mufflers typically use a number of baffles and chambers to cause harsh sounds to reverberate back at each other, cancelling out the sound waves. Enough tech babble. A good aftermarket muffler is responsible for making your truck sound super sweet, giving it that awesome performance growl. We find some customers are more concerned with the sound of their truck or Jeep than that actually performance or horsepower, and there's nothing wrong with that. If you are that guy, start here with your exhaust modification. While you could just replace your muffler with one that sounds the way you want your vehicle to sound, you could also opt for a full Axle-Back Exhaust system, which will include your muffler and an exhaust tip and typically a mid-pipe to connect into existing downpipe. If you are looking for performance, there are mufflers that produce great tone or growl while minimizing their backpressure, but there is always going to be some backpressure with a muffler because of their sound deafening nature. Find the sound you love and run with it, man!

Tailpipe or Exhaust Tip

Finally we right the bitter end, the part most non-enthusiasts most often think of when they hear the word "exhaust"--the tailpipe. Also known as an exhaust tip, this piece is likely the only part of the exhaust system that will be visible while you are driving, unless if you have a massive lift kit installed. This piece thus becomes all about aesthetic choice. If you like chrome, there are a number of exhaust tips for you. Prefer something in a darker color? Check out some black polished finished tailpipes. These pieces also come in variety of shapes, but they don't really effect your performance as this is the part of the exhaust system that opens up to the world and lets the hot gases escape. So just pick on that you think looks the sickest and go with that one. You really can't screw this part up... much.

Helping You Pass Exhaust 101

Is this gonna be on the test?

Don't worry there is no test. Well, technically life is the test in this case. And now that you know some of the basics, you are ready to graduate to replacing some or even all of your exhaust to aftermarket upgrades. The question may be which is right for you: a Header-Back Exhaust, Downpipe Back, Turbo Back, Cat-Back, Axle Back, or DPF Back? And if you don't know what all of those terms mean, we'll be covering that in our next article in the Exhaustive Series: Performance Exhaust Systems! Ready to make a purchase already? Click on the item above to be taken to a category page to shop for those specific products or enter your make/model and do a search for what you want. Either way we've got what you need at Midwest Aftermarket.