Straight Piping 101: What You Should Know

If you’re modifying your car for more power, upgrading your exhaust system is one of the first things you should do. Upgrading your exhaust can be a relatively cheap modification to make, and is an easy way to squeeze a little more power out of an engine that already has a few performance mods.

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A straight pipe exhaust is a serious modification that is generally only seen on race-tuned cars. This kind of exhaust is the most free-flowing type of exhaust system, which is useful for cars that spend most of their time high up in the rev range. These exhausts are also the loudest type of exhaust system available.

In this article, we’ll be taking an in-depth look at straight pipe exhausts and explaining what they do, how they work, and other information you might need if you’re thinking of installing this type of exhaust on your own vehicle.

What’s a Straight Pipe Exhaust?

As you probably know, a regular exhaust system is more than just a simple pipe. Modern exhaust systems typically contain multiple catalytic converters and mufflers, with the goal of reducing harmful emissions and making the engine run more quietly.

Straight pipe exhaust systems, on the other hand, literally are just simple pipes that run from the exhaust manifold out to the end of the car. They contain no catalytic converters or mufflers and are a lot louder than other types of exhaust systems.

As we’ve mentioned, straight pipe exhausts are very free-flowing, meaning there is usually little to no back pressure within the system. This is good for performance engines that tend to rev pretty high since high-revving engines produce a large flow of exhaust gas that can negatively affect engine performance if it is restricted.

Having a free-flowing exhaust for a high-revving engine is important for proper scavenging. When talking about engines, “scavenging” is when the exhaust gas leaves the cylinder and the air/fuel mixture flows in.

In an engine that is scavenging properly, the exhaust gas leaving the cylinder creates a vacuum effect that helps to pull the air/fuel mixture into the cylinder.

Scavenging only happens when the exhaust gasses are flowing at the right speed, however, and this is determined by both the size and restrictiveness of the exhaust system and the speed at which the engine is turning.

If the exhaust isn’t flowing quickly enough, it’ll fail to create any kind of vacuum, and if it’s flowing too quickly then the scavenging process isn’t nearly as efficient.

Why Would You Need Straight Pipes?

If we’re being honest, there’s no scenario where you’d ever need a straight pipe exhaust specifically. Certainly, there are situations where having a straight pipe exhaust makes a lot of sense, but there’s no situation where installing a straight pipe is your only option.

In general, you’ll only want to install a straight pipe exhaust on a car that has been tuned for performance. Straight piping a regular street vehicle doesn’t really offer a ton of tangible benefits, and in fact, can have several disadvantages.

OEM exhaust systems in street cars are optimized for scavenging, and installing a straight pipe exhaust that isn’t optimized for the engine it is attached to is a great way to mess up your scavenging. Exhaust that flows too freely for the engine can decrease your low-end torque and actually make your car a bit slower during everyday driving.

Straight pipe exhausts really only work with race cars, but straight pipes aren’t your only option in this situation. You might also want to consider installing a performance exhaust system in your car, which offers a few advantages over a straight pipe system; we’ll go into more detail about performance exhaust systems later in this article.

Pros and Cons of a Straight Pipe Exhaust System

We’ve already talked a little bit about some of the advantages and disadvantages of straight pipe exhaust systems, but in this section, we’ll go into even more detail about them. Here’s what you should keep in mind when deciding whether or not you want to install straight pipes in your car:

Pros:

Improved performance: The main reason why anyone would install a straight pipe exhaust system in their car is the performance benefits. As we’ve already mentioned, having a free-flowing exhaust is necessary for high-performance engines, as it helps reduce back pressure within the engine.
Reduced weight: OEM exhaust systems typically contain a bunch of extra components like mufflers and catalytic converters that make the car more usable for everyday driving. However, these extra components add weight to the vehicle. Since straight pipe exhausts don’t contain any of this stuff, they’re usually lighter than regular exhaust systems.
Better sound: If you like hearing the pure, unadulterated sound of your engine, you can’t go wrong with a straight pipe exhaust. Many OEM exhaust systems dilute the sound of the engine through the use of mufflers and resonance chambers, but with a straight pipe exhaust you’ll be able to hear your engine as it was meant to be heard.
More aesthetically pleasing: The simple truth of the matter is that most OEM exhaust systems just don’t look that cool. Straight pipes, on the other hand, almost never fail to make a car look sportier and more aggressive. If looks are important to you, you’re probably going to prefer the style of a straight pipe exhaust.
Improved fuel economy: Believe it or not, straight piping your car can actually make it more fuel efficient. This is mainly due to how the decrease in back pressure allows for more efficient combustion. You may not see huge gains to your fuel economy, but you’ll definitely see at least some improvement.

Cons:

Excessive noise: Straight pipe exhaust systems do let you hear the pure sound of your engine, but they also make your engine a lot louder. Aside from the fact that most cities have laws restricting how loud your engine can be, you might find that an excessively loud car is just kind of annoying and tiresome to drive.
Increased emissions: As you know, OEM exhaust systems are designed to eliminate as many harmful byproducts as possible from your car’s exhaust, while straight pipe systems are designed for no such thing. A car with straight pipes is going to be a lot worse for the environment.
Added expense: Replacing your car’s exhaust system isn’t the most expensive modification to make, but it’s certainly not a cheap one either. If you find a shop that is willing to do this for you, expect to pay at least a few hundred dollars for a low-end straight pipe exhaust. Because of the questionable legality of straight pipes, many shops won’t even perform this kind of modification at all.
Affects resale value: If you’re planning on selling your car at any point, it’s a good idea to hang on to your old exhaust system so you can swap it back in before selling. Even if they make the car faster, modifications generally decrease the resale value of cars. Plus, there’s no guarantee that the person buying your car actually needs or wants a straight pipe exhaust system.
May not be legal: We’ve mentioned this already, but straight pipes on street cars are usually illegal to have. Not only can they violate noise restrictions, but because they lack any kind of emissions control they also produce illegal amounts of harmful emissions. If you take a straight piped car to a smog check, odds are it’s not going to pass.

Is a Performance Exhaust System Better Than Straight Pipes?

While straight pipe and performance exhaust systems are both designed with performance in mind, these two types of exhaust systems are considerably different.

Straight pipes do away with parts that can restrict airflow like catalytic converters and mufflers, while performance exhaust systems retain these parts or replace them with less restrictive alternatives. Essentially, performance exhaust systems toe the line between OEM exhaust systems and straight pipes.

You may see performance exhausts referred to as “cat-back” exhausts. This term refers to the fact that performance exhausts usually replace everything that is located behind the catalytic converter. These parts include the muffler, the length of pipe connecting the catalytic converter to the muffler, and the exhaust tips.

Let’s do a quick comparison between straight pipe exhausts and performance exhausts and see how they differ in terms of their key areas.

Noise

Straight pipes deliver a purer sound than performance exhausts, but at a much higher volume. If you’re installing a straight pipe in a track-only car, this isn’t a big deal, but for a road car you’re probably going to want to install a performance exhaust instead.

A performance exhaust will definitely make your car a bit louder, thanks to a less restrictive muffler, but not so loud that it can’t be driven on the street. If you want your car to be tolerable during daily driving, a performance exhaust is definitely the better option.

Emissions

As we’ve mentioned, straight pipes don’t contain any catalytic converters or anything else that can be used to reduce emissions; they’re just straight lengths of pipe leading from the exhaust manifold. In contrast, performance exhaust systems usually include everything necessary to make the car emissions-compliant.

In terms of emissions, there’s really no contest. If you want your car to be road-legal and as environmentally friendly as possible, you’ll need to go with a performance exhaust.

Performance

The question of which type of exhaust actually performs better is probably the most important one when it comes to comparing these two exhaust types. After all, both straight pipes and performance exhaust systems are built to make increased power before anything else. So which type of exhaust is actually better at it?

Straight pipes have the potential to offer bigger power gains than performance exhaust systems, but only if the car is tuned properly. With an untuned car, the difference in power you’re going to get from a straight pipe exhaust versus a performance exhaust is going to be negligible.

Cost

If you’re comparing a straight pipe exhaust and a performance exhaust in terms of price, they’re generally about the same, as long as you’re buying them from an actual parts manufacturer. However, if you want to go the DIY route, you might be able to save yourself a ton of money in parts and labor costs.

The downside to this, of course, is that you actually have to put in the work yourself to fabricate and install your exhaust system, but if you’re an experienced mechanic and you like doing this sort of thing then this might not be such a huge downside for you.

Summary

So, which one of these exhaust types is actually better? Overall, we think that performance exhaust systems are better, although it really depends what you’re looking for in your exhaust upgrade.

If your primary concern is just making more power, then a straight pipe exhaust is probably the option you’ll want to go with. The same can be said if you’re mainly concerned with keeping the cost of your upgrades down, especially if you choose to go the DIY route and fabricate your own straight pipes.

However, if you want your car to actually be tolerable as a daily driver, you’re probably going to prefer a performance exhaust. The sheer volume of a straight pipe exhaust can make your car borderline undrivable on regular roads, and there’s also the fact that straight pipes are illegal to have on road cars in most places.

To put it simply, if you just want to make power and are planning to use your car only on the track, straight pipes are the best choice. Otherwise, a performance exhaust system will likely fit your needs a lot more.

How Much Does a Straight Pipe Exhaust System Cost?

The price of a straight pipe exhaust system can vary like crazy, depending on several factors. The materials used to make the pipe make a difference, as does the model of vehicle you’re installing the exhaust on, the city you live in, and whether or not you’re trying to make these modifications yourself.

You can save some money by fabricating and installing the exhaust yourself, although you really shouldn’t attempt this modification on your own unless you’re skilled at welding and working on vehicle exhausts. Getting a shop to handle this is usually a better idea, although you then have to factor in the cost of labor.

At the low end, a straight pipe exhaust system will probably run you somewhere around $300-500, but again, depending on a few things you may end up paying somewhere in the area of $1,000-1,500 to straight pipe your car.

As for the performance exhaust, expect paying around $600 – 5,000

What Size of Straight Pipe Do I Need?

This depends on the size of your engine and how much power it makes, but there’s a general rule of thumb you can follow that will help you determine approximately what the diameter of your exhaust should be.

Basically, for every 100 horsepower your engine makes, you’ll need 1 inch in diameter within your exhaust pipe. Therefore, for a car with, say, 600 horsepower, you’ll need an exhaust system with a total diameter of 6 inches (or two 3-inch pipes if you’re running dual exhausts).

This 1 inch per 100 horsepower rule is just for rough estimates, however; if you want a more accurate estimate of the size of the exhaust pipe you’ll need, we’d suggest checking out this handy exhaust size calculator.

You can use this to calculate the size of the pipes you’ll need based on your car’s power output and the number of exhaust pipes you have. You can also use the calculator to determine the maximum amount of power your car can handle based on your exhaust diameter and the number of pipes you have, which is pretty cool.

Can I Sell a Straight Piped Car?

This is a slightly tricky question to answer. Ultimately, this depends on what the laws are regarding straight pipes where you live. Not every place requires emissions testing for every car, so in many areas it’s totally legal to sell a straight piped car.

Other places prohibit dealerships from selling cars that aren’t road-legal, but these laws might not necessarily apply to private sellers.

The real question here, though, is how easy is it to sell a car with straight pipes? In most cases, it might be harder than you think. Heavily modified cars don’t usually retain much of their original value, and there’s also the fact that most people probably aren’t interested in a car that is too far removed from its stock form.

Even if you’re trying to sell your car to another automotive enthusiast, you have to take into account the fact that your vehicle preferences and theirs are probably going to be quite different. People generally prefer to modify cars to their own liking, not someone else’s.

If you do plan on straight piping your car, you should hang on to the original exhaust system so you can swap it back in if you ever plan on reselling.