Are aftermarket Exhausts Even Worth It?

(car engine revving) - Oh, it sounds like a BMW N55. (car engine revving) That sounds like an RB25. (car engine revving) Oh, that's a baby Toyota 2JZ. (car engine revving) (Eddie speaking without microphone) - Is something wrong? I did not hear anything. How did I know that without seeing any of those cars? Well, for one, because I wrote this episode and those are my cars and my roommates' cars, but two, because I could hear them. The sound of the car's exhaust is basically its mating call. The sound of your car is a big part of who your car is.

It's like his signature. Having a fresh, recognizable exhaust sound is one of the main reasons why an

aftermarket

exhaust is one of the first upgrades many people make to their car. They come in different shapes, sizes, and of course prices, but they all promise more or less the same thing: a little more power and an overall better and generally louder sound. But will they always give you more power? And if so, how? And why does one pipe sound different from another? Today we're installing a $600 MagnaFlow rear cat exhaust on the Miata. And along the way, I'll answer all of those questions and more and then we'll test drive it and I'll give you my opinion on whether or not it was

worth

it for the old Money Pit Miata.

And hopefully, that will give you enough context to make the same decision for yourselves. I'm Zach and this is Money Pit. Let's do it. (thunder) (car engine revving) Now today's challenge is to make the Miata sound like this. Alright, so we're kicking around with our original exhaust right now. Listen. (car engine revving) It really doesn't seem like much. So we want to put an exhaust on it that flows better than the original and sounds better than the original. So let's go back to the garage and I'll show you what we have. Alright, this is the exhaust we have, it's a MagnaFlow.

It costs around $590. It is made of stainless steel so it should not rust or corrode. Let's remove the bubble wrap and see what we're looking at. Court! Bright. As you can see, we have some welds here. They look good. I think this is welded by robots, robots tend not to make mistakes. So that's great. So the build quality seems pretty good and it should really cost $600 for a jack, not the cheapest thing in the world. Let's get the rest out. Oh what is this? A little stopper for a homeless man. So this is our resonator. They are used to cancel harsh and drone frequencies.

And you know a scrape. That's a great scarf. We have a big horn and a resonator and we just have what is it? A 1.8-liter four-cylinder. I think this should be pretty quiet, which is honestly what I want. I don't want to make so much noise with the Miata. Yeah, man, it's a 100-horsepower four-cylinder. We don't need to shout about it. We can just be quiet. We can just (speed up) Like this. So the way a resonator works, basically the exhaust flows through and you can see this resonator directly. But this outer shell is packed with material.

Sometimes like fiberglass or something that absorbs sound and energy. So as the exhaust passes through, the packaging material absorbs a lot of sound. It's really simple. This is a cat back exhaust for a 1994 Miata. Now when I say cat back, what does that mean? It means what it says. The exhaust starts at the end of your stock jack and runs the rest of the way to the rear. We'll stick with the stock cat because, again, we're only making 100 horsepower right now. So we agree with the emissions team. It might gain us a horsepower or two. It should at least give us some sound.

But the installation will take us about 10 minutes. Ten minutes to install. - Do you want to place a bet? - No. Oops too far. So my driveway is sloped down and we are lifting the back end to put in an exhaust. That's why I put something in front of the front wheel so it couldn't roll. It's always good to give it a little shake. Make sure your job is stable. Alright, let's get this old piece of (bleep) out of the way. Alright, this is our catalytic converter. So let's replace everything from here back. So I'm going to start here and pull out these nuts.

But the first thing you should do is use some penetrating oil, ideally the night before or

even

a few days before you start. And this will seep into those threads and help release the rust so you don't end up stripping the hardware or rounding off any of the nuts. Good, now our balls are loose. Now we need to remove the exhaust from its rubber mount. So we'll add a little bit of lubricant and then force it in with some pliers, screwdrivers, and our hands. Okay, I think we have one more left. Okay, now (laughs) Is there a ridiculous way to do this?

Now, there has to be a way. Oh, so close. Do you think it will be enough? Eddie thinks so. - I know. -Eddie knows it. Eddie is the smartest guy who ever lived. Whoa (bleep) Okay. The old exhaust is out. That was pretty easy. Even with a couple of small hiccups. I think it's been 15 minutes. So disassembly, installation, all this is not so bad. So so far it's

worth

it. Alright, let's talk about some of the pros and cons of an

aftermarket

exhaust to see what all the fuss is about and see if it's really worth it.

The objective of these is to let the engine breathe better. The exhaling part increasing the diameter of the pipe. They will also make the muffler design flow a little more freely and eliminate any unnecessary curvature or, you know, sharp turns that you don't need to have. Just to try to decrease the restriction and improve the overall flow in the exhaust system. Now, improved flow and less restriction can mean, you know, some extra horsepower up top. They also tend to be louder than the originals due to the decreased restriction and change in muffler design. That part is obviously awesome as long as the muffler is designed to sound good and the engine you're putting it on is capable of making good noises.

That's a big part of it. Visit YouTube and Google and find examples of your car with specific

exhausts

. Chances are, if someone makes an exhaust for your car, someone bought it and someone took a video of it. Now, in addition to being louder because we like it, being louder can also save your life. You may have heard the phrase loud pipes save lives and that can be true, especially on a motorcycle or in a small car like the Miata, making a little noise can cause someone who didn't see you coming to hear you coming and do not throw away. in front of you or run over you all together.

Well, usually aftermarket

exhausts

are made from aluminized steel or stainless steel, both materials that last a long time, which is why many aftermarket exhausts come with lifetime warranties like this because the materials are just good. Now, okay, let's talk about the cons. Some disadvantages of the matter. Let's talk about disadvantages, honey. Scammers can be expensive. This, just for the Miata was $600. It's not cheap, it's nothing. Generally speaking, the price of the exhaust and replacement parts in general are proportional to the price of your rig. So, cheap cars, their exhaust gases will be a little more expensive.

Other than that, you know, there are some people who just don't want to make any more noise. I know it sounds ridiculous, but what I'm talking about is drones. (buzz) That's a drone. Automakers and OEMs invest a lot of time, money, and brainpower into manufacturing original parts, and the truth is that original parts are often really impressive in many ways. They always tend to land squarely at the crossroads of comfort, reliability and power, which is pretty impressive. Once you replace the exhaust, you move away from that crossroads of comfort and reliability and toward power, which is a fun path, but it's definitely a lot louder.

But how do you know if you need an escape? Honestly, it really depends on the platform. So you'll have to do some research. Some cars, like old big V8s or cars that have a very restrictive factory exhaust, can gain a lot of power with just an exhaust, while some cars don't gain much. So what kind of exhaust do you need? A jack backrest, an axle backrest, a headrest backrest, a turbo backrest? Literally, the AL on those just means that the escape starts at the end of that thing and continues to the end of the escape.

And what you need depends on your goals. The more of the exhaust system you replace with free or flowing parts, the more power you can make. So what size exhaust do you need? Well, the answer is that there is a lot of math involved in figuring it out, but in practice, there are many online calculators and graphs that will help you determine what diameter pipe to use for a given power level and engine displacement. So in that sense, it's pretty simple. Simply search for the exhaust diameter calculator and you will find everything you need. Let's put this on.

First we will install this tube to the catalytic converter. I think you should be able to do it this way and then we'll put the back half on since the MagnaFlow comes in two pieces. Now, this brace is coming back up. Isn't the alignment so perfect? So, giving it the old persuasion, sometimes we will have a car that stinks. Like right now. (laughs) Before we finish installing this exhaust, let's take a minute to talk about one of the most enduring myths in all of automotive history. Back pressure. The myth is that you need back pressure to generate power or more specifically, low end torque and back pressure is the resistance that the exhaust fights as it exits the tailpipes.

Back pressure is actually counterproductive to generating power. You don't want any restrictions on your escape. Think of a Top Fuel dragster with open heads. There is no back pressure there. Okay, but then why do people lose some of that precious low-end torque by increasing the diameter of their exhaust? Well, first we must understand that the exhaust flowing through the pipes is not a constant stream of exhaust. It's pulse. Every time a cylinder completes an exhaust stroke, a pulse, a pulse, a pulse, pulse, pulse, pulse. And every time one of those little baby pulses shoots out the exhaust, it creates a little vacuum pocket behind it.

And just like in the NASCAR draft, if you can catch up to the guy in front of you, you can take advantage of his little vacuum pocket. Now we want a lot of vacuum behind each of our exhaust pulses so that the vacuum created can help pull the next exhaust pulse out of the combustion chamber. So this little vacuum bag, NASCAR writing material, is called a scavenger hunt. And it's most effective at low RPM because once you reach higher RPM, the exhaust starts to flow, more like a steady stream than a pulse. Okay, so how do we increase the speed of the escape pulse?

Well, think of your exhaust as a garden hose. Okay, so we increase the exhaust gas flow rate. Damn, I gotta... You got a weak flow, man. - Yes I know. Well, I got it, I got it. Oh God. (Laughs) Now, when the hose is fully open, we use the entire diameter of that hose. We have a very good flow. There is very little back pressure and this progresses quickly. We have a lot of flow here, but what we don't have is a lot of speed. This is coming out pretty slowly. Now, when you decrease the diameter of the hose without changing anything else, you clearly change the speed at which the fluid travels there.

The same goes for the exhaust, if you decrease the diameter the exhaust gases will be forced to travel faster than when the exhaust pipe is fully open. Great flow, terrible speed. Okay, wait a minute. We want a small diameter exhaust to increase velocity and increase vacuum behind each pulse. So we get the sweep effect, but we want a large diameter so we don't have back pressure? Exactly. And the problem is that you obviously can't have it both ways. So an agreement must be reached, like so many things in the automotive world. So it's been a long road to say you don't want counterpressure, but you want speed to get some knockout effects and it turns out you get each of those things in opposite ways.

Well, the end. Let's put this on. Before we install this, we're going to make sure it's really clean because if we get any big old handprints or smudges here, and then we heat it up for the first time, those things are going to burn all the way through. So if I put a fingerprint there and we drove for the first time, that fingerprint would be there pretty much forever. So you don't want that. Just wipe it off quickly before it gets hot. So, put some lubricant on our hangers. Always helps. So whenever we do an exhaust installation or something where there are multiple pieces, you want to leave all the hardware you're working with not completely tight so you can adjust a little bit.

Now we have all the pieces in place and all we have to do is tighten the exhaust fittings. So, this hardware and that hardware there. And then the time comesto make some noise. Well, then let's listen and see if all this has been worth it. (car engine revving) Oh, that sounds pretty good. (car engine revving) It's not that bad. It's not unpleasant, it's not very noisy. Complements the intake sound. I can still hear the entrance. (engine revving) That sounds pretty good. Let's take him for a ride. (engine revving) You know what? That's exactly what I wanted from an escape.

It's discreet, it's not terribly loud. Oh, it has a nice base tone. (engine revving) Makes this sound good. (engine revving hard) (engine revving smoothly) Now, I don't feel any difference in power. I'll tell you that. But I didn't expect it. The goal of this exhaust, in our case, is not to give us more power now, but to allow us to make more power later when we add a turbo and whatever else we do to this thing. Well, sweet. And on that note guys, I want to say thank you very much for watching the show. I hope you are learning.

We are learning a lot by doing it. Make sure you subscribe to Donut and ring the notification bell so you know what's coming. We are posting things every day. And I appreciate you guys being so involved in the comments and talking about what's going on and telling me what you're working on. Keep it up. Tell me what you're doing, how you're spending your time in quarantine. Add the comments, I'll be there commenting. I'm always there. And, if you like this super sick and totally awesome t-shirt, you can buy it at shop.donut.com. Join our gang with impulse creeps and you can be one of us.

Follow me on Instagram @zachjobe Follow Donut @donutmedia and see you in the comments. Bye bye.