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Cat-Back vs Straight Pipe: Which Is Best for You?

Close up of a dual exhaust pipe with smoke coming out on a black car

If you’re looking into different performance-boosting mods for your car, you might have stumbled across exhaust system swaps. Two of the bigger options for everyday drivers are cat-back and straight piping exhaust systems.

Straight piping should be reserved only for track cars since it’s an illegal mod to perform on daily drivers. It’s illegal because it removes the muffler and catalytic converter as part of the swap. For most people, a cat-back system will achieve everything they’re looking for, and it’s legal. Either option can boost your performance, improve your fuel efficiency, and give you a better exhaust note.

In this guide, I’ll explain the difference between the two, describe why people swap their exhaust systems, and help you to understand which option is best for you.

How Your Exhaust System Works

Before getting into specifics, I want to run through a quick definition. By understanding how your car’s exhaust system works, you’ll be able to make the right decision on which system is right for you.

In any vehicle that uses an internal combustion engine (ICE), toxic gases are created in the engine thanks to the combustion going on. In addition, a ton of noise is created.

Your car’s stock exhaust system is there for two purposes:

  1. Keep the noise as low as humanly possible
  2. Remove all of the toxic elements in the smoke byproduct

The noise is kept down through the muffler. The muffler is a housing that’s filled with different components like a resonator, perforated plates, and different chambers. It uses acoustic engineering to dissipate most of the noise.

The toxic scrubbing is done in the catalytic converter. This is another block that gets installed in your exhaust line. It comes before the muffler, and it uses patterns of precious metals and chemistry to strip away the toxic elements. You’re left with breathable air coming out of your tailpipe. The cat does nothing to dampen the noise of the exhaust.

Hi resolution illustration diagram of the exhaust system of a car including the catalytic converter, pipes, muffler, resonator, hangers, and clamps

Looking at Your Stock Exhaust System

In a stock exhaust system, a smaller diameter pipe runs from your engine to the catalytic converter, then the muffler, then out of your tailpipe.

Typically, a stock exhaust system is an afterthought when it comes to designing your vehicle’s undercarriage. As a result, you’ll see the line do multiple turns and sometimes sharp turns just to fit on your car.

It’s held together with different pipe hangers, fasteners, and mating flanges. The assembly has to be airtight and sealed, or else toxic gas can escape and lead to serious health issues.

What Is Straight Piping?

Now it’s time to start explaining the alterations you can make. First up, let me address straight piping.

If your car has a straight-piped exhaust system, then you might not spot any of the parts I was just talking about. That’s because part of the straight pipe conversion entails removing the muffler and catalytic converter.

In a car with straight piping, a pipe carries the exhaust from the engine, directly to the tailpipe. There is no sound dampening since the muffler is removed, and there’s no scrubbing of the toxic chemicals since the catalytic converter is removed.

Due to these two facts, it’s illegal to have straight piping on a streetcar — it’s reserved for racecars.

The reason behind straight piping is that the lack of bends, muffling, and converting gives a big performance boost. There is no backpressure issue, and air flows very freely away from the engine. This results in more horsepower and a more immediate throttle response.

It also means that your car will be significantly louder and boast a deeper exhaust note.

Fabrication and installation of a stainless steel straight pipe exhaust with a bi-furcation and custom welding visible from the underbody

What Is a Cat-Back System?

Cat-back is a term that comes from “catalytic converter” and the back of your car. By definition, it’s the stretch of exhaust piping after the cat all the way to the exhaust pipe.

When you do a cat-back conversion, you’re basically replacing all the pipes after the catalytic converter.

Compared to stock, a cat-back exhaust system has larger diameters, smoother curves, and improved mufflers. It’s important to note that mufflers are still included in a cat-back system.

The main purpose of a cat-back is to reduce backpressure, keep your car quiet, give the exhaust a better tone, and give you a performance boost. You might also notice better fuel efficiency and a slightly lighter car.

Car chassis on the lift with the exhaust system, brakes, and wheels all visible from the underbody cat-back exhaust with muffler

Quick Comparisons, Catback vs Straight Piping

To better understand which option is best for you, let’s do a quick comparison. I’ll look at some different categories and compare the two options.

Installation Price

The price of installation can vary a lot, especially if you DIY the swap. In general, you’ll spend more for an entry-level straight pipe conversion, but a high-quality cat-back is way more expensive.

The rough cost range near me for a mechanic to do the work is about $1,000 to $2,000 for a straight pipe swap and $250 to $4,000 for a cat-back conversion.

For straight piping, you just need the right kit which includes a run of pipe from the engine to the tailpipe. For cat-back conversions, there are a few pieces that need to be purchased and installed together.

Overall Noise

The noise difference is staggering between these two options, especially if you compare them both to your stock exhaust system.

Your stock system aims to make the exhaust noise as quiet as possible. After all, auto manufacturers are trying to sell their cars to everyone on the market, and a lot of people hate loud exhausts.

A straight-piped car is the loudest option, by far. With a complete lack of a muffler, there’s nothing dampening the sound at all.

A cat-back system is louder than stock, but that’s just because it uses a different kind of muffler. The end result will still be legal to drive, even during quiet hours in your area.

Total Emissions

Your car’s emissions can determine its legality. It’s a measure of how many harmful gases come out of your tailpipe when your car is running. With a functioning catalytic converter, your emissions should be fine, and your car will pass inspections.

With no catalytic converter, the smoke will be toxic and your car will be illegal to drive on public roads. You can probably see where I’m going with this.

Straight piping removes the catalytic converter, so its emissions are much higher. That means more greenhouse gasses, more toxic fumes, and more legal trouble if you drive on a public road.

A cat-back system doesn’t touch the cat at all. The modification starts where the cat ends. As a result, your emissions will be fine and unchanged.

Car emissions test being performed on a white hatchback car with the diagnostic computer visible and the emissions hose hooked up to the muffler exhaust

Performance Enhancement

One goal for both of these conversions is to boost your car’s performance. With that said, either option is great, and either will boost your performance.

The difference is that a little bit of tuning can further improve your performance if you have a straight pipe system. It has fewer bends and fewer components to go through, hence the bigger boost.

Final Fuel Efficiency

Both of these options will improve your fuel efficiency by a little bit. Keep in mind, it won’t be a huge difference.

This happens because the swap will reduce your back pressure and strip some weight from your exhaust system. With less weight and a better flow, every gallon of fuel burnt can get you further.

Street Legality

The biggest comparison, in my opinion, is the legality of the mod. As I’ve mentioned a few times so far, a straight-piped car is illegal to drive on public roads, and it’s impossible to hide the mod. The noise will be extremely loud and the lack of a catalytic converter can get you in huge trouble.

A cat-back is fully legal, as long as you replace the muffler when you take off the old one. This system still improves the noise and tone of your exhaust, but it does it legally. Since it leaves the catalytic converter intact, you don’t have anything to worry about.

The Impact of Your Exhaust Piping

Although it might not seem like it, swapping your exhaust piping can make a significant difference. When I was younger, I swapped to a cat-back system with exhaust tips and I could feel the difference when I got the car back.

Everything felt smoother, the throttle was more responsive, and the noise was more impressive. Just a few hundred dollars can make a pretty big difference.

Your exhaust system is responsible for a lot. By improving the system, you are improving features such as:

  • Throttle response
  • 0-60 time
  • Acceleration and overall performance
  • Fuel efficiency
  • The noise and tone coming from your tailpipe

Which Is Best for You?

By now, you probably have a good idea of which option is right for your needs.

Straight piping is perfect for people who need to get some extra power on their track car. Since it’s an illegal mod, you can’t do it on your daily driver or weekend ride. However, it will give you the biggest performance boost for a car you only use on the track.

You should go with a cat-back system if you want to boost the performance, fuel efficiency, and sound of your daily driver. It’s a reliable mod, so you aren’t risking a big problem in the future (which can be an issue with other mechanical modifications).

Can You DIY An Exhaust Swap

When I was talking about pricing earlier, it might have come as a shock. As a result, you’re probably wondering how much of this swap you can DIY.

Well, if you’re an experienced welder, designer, and fabricator you can DIY the whole project from start to finish. You won’t even need a kit, assuming you have piping experience.

To do the swap, start by removing your current setup. For a cat-back, it could be as simple as loosening a flange and a few pipe hangers. Doing so should free up the tail-end of your exhaust system, allowing you to remove everything.

With straight piping, uninstalling starts at the exhaust manifold. From there, you’ll need to bend, weld, and install a new run of pipe that goes all the way to the tailpipe. Kits are designed with certain bends to avoid parts of your specific car’s undercarriage, but the run could also be designed on your own.

To install the new parts of a cat-back system, you’ll need more. You would need larger pipes to run to the mufflers, new mufflers, new pipes to go from the mufflers to the tailpipe, and new tailpipes.

To get the performance-boosting results, you’ll have to upgrade the size of the line for all of these replaced parts.

If you want a simple answer, there’s nothing stopping you from DIY’ing a full exhaust swap, as long as you’re not afraid of welding and fabrication. If you purchase a new kit, then the swap might be as easy as installing a few bolts and pipe hangers.

I’ve done my own cat-back swap in the past, and it wasn’t really tricky. Maybe you should get a quote from your local shop and make the decision from there. If they’re charging you hundreds more for their manpower, then it might be worth thinking about DIY’ing it.

Young guy welder in a checkered red shirt welds a stainless steel exhaust pipe for a car using a welder gloves and helmet on a workbench

Will An Exhaust Swap Void Your Warranty?

Another question I get a lot is which modifications can void your car’s warranty. If you didn’t know, newer cars have warranties that cover a lot of expensive repairs within a certain mileage and year range.

In the past, I had parts of a new-ish car fail, and the warranty covered every penny of a thousand-dollar repair. To put it simply, it’s a great way to save a lot of money if there is a defective part within your vehicle.

It’s separate from insurance, and you’re not paying directly for a warranty — it’s just a courtesy that car manufacturers extend to protect you from any mistakes within their vehicle.

With that being said, certain actions can void the warranty, or make it so that the warranty doesn’t cover you anymore. If you loosen all the bolts in your engine bay and take out all the sensors, it would be insane for the car manufacturer to cover the cost of whatever damages happen.

Following that train of thought, certain modifications will cause the manufacturer to stop covering repairs.

The rule of thumb is this: if your modification can be directly linked to the damage caused, then the repair is outside of the warranty. There are plenty of cases that go against that rule, so you should do more research if you want an exact answer.

For swapping your exhaust system, it’s the same story. Generally, as long as you do a cat-back swap, then the warranty will still be intact. If you do a straight pipe exhaust swap, then there’s a good chance that the auto manufacturer will deny your claims and void your warranty.

Conclusion

Now you know everything about cat-back exhaust systems and straight piping systems. I just covered what they are, how they compare to your stock exhaust, why people perform the swap, and which option is right for you.

If you have any questions, please leave a comment below. For people who want to learn more about their car and the different mods that can be done, check out the rest of my blog. In addition, see a list of products that I highly recommend.

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References:

Complete Car

Straight Pipe vs. Catback Exhaust: Which One Is Best For You?

Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

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