A cat or catalytic converter is essential to every car’s exhaust system. It allows you to drive without worrying about releasing toxic exhaust fumes or getting fined for failed emissions tests.
However, a cat can also restrict the maximum power that your car has in store. In doing aftermarket exhaust mods, you’ll have the option to either go catback vs catless.
You may already know that both catback and catless exhaust will boost your car’s power, but there are other pros and cons you should consider further. Read on as we give a helpful comparison of these popular exhaust mods below.
| COMPARISON | Catback Exhaust | Catless Downpipe |
| Catalytic converter | Yes | No |
| Road legal | Some states | No |
| Performance | At least 2-3hp to 50hp boost | Up to 25 hp increase (without tune)
Additional 50 or more horsepower (tuned) |
| Emission testing | Stock cat will pass emission tests
High-flow cat may pass visual and OBD2 test but may fail sniffer |
Zero chance of passing emission tests |
| Sound | Loud but slightly muffled | Bigger and louder sound than catback |
| Cost | From $300 and up | Starts from $150 |
Table of Contents
Catback Exhaust
A catback exhaust is an aftermarket modification made to gain a few powertrain boosts. The term “cat back” denotes the section where the mods are made– at the back of the catalytic converter through the exhaust tips.
Here are some essential details about catback exhausts:
- Going catback means swapping your stock pipes with wider, less bent pipes and a less restrictive aftermarket mid-pipe or muffler. These alleviate the back pressure and promote better exhaust airflow for better performance.
- This exhaust system allows for better sound improvement. It boosts horsepower without affecting the car’s emissions since it does not remove the catalytic converter.
But while the catalytic converter isn’t removed, you can still swap the stock cat with a less restrictive aftermarket one or use a system with only one cat. Pairing it with sports unit mufflers will give a more aggressive and sporty note.
Catless Exhaust
A catless exhaust system is exactly as it sounds. This aftermarket exhaust completely removes the catalytic converter from the system to significantly relieve back pressure.
The lack of a cat allows maximum exhaust flow and a quicker spool for the turbo.
- Once you go catless, expect that you’ll get some power boost due to a less restricted exhaust system, not to mention the reduced weight of not having a catalytic converter.
- You’ll also get a louder exhaust note as this system is usually paired with larger piping that also contributes to better sound flow. However, you just have to deal with the smell of gasoline as your fumes don’t get emission treatment.
The major downside of going catless is that you can no longer drive your car on public roads, as it’s illegal to do it without a catalytic converter in all 50 states. A catless downpipe is usually used for track only and not for a daily driver’s car.
Differences Between Catback and Catless
To better compare catback and catless exhaust systems, we differentiate them in their most distinctive aspects below.
1. Performance
When car enthusiasts do exhaust mods, they are most likely after the powertrain boost that an aftermarket pipe would give. Here, we look at actual dyno tests to see how performance is improved between a catless vs catted downpipe.
Catback
Generally, a cat-back exhaust is expected to deliver as low as 2-3 horsepower up to 50 hp boost or a 2-5% power increment on average. One test on a 100% stock Civic Type R FK8 netted an 11.5 wheel horsepower increase after installing a 3” catback exhaust.
Another owner revealed he gained 40 more horsepower in his 2016 Civic, which is tuned and installed with a catted downpipe.
Catless
Catless exhausts are estimated to provide a 15-20% increment from the original horsepower. Or up to around 25 hp without tuning and 50 hp tuned.
For reference, one BMW F10 M5 peaked at 586 whp from its baseline result of 527 whp– an impressive 59 whp jump after a catless downpipe installation.
This particular M5 is also tuned and equipped with other performance mods like center pipes, four 102mm exhaust tips, and an aftermarket intake while sporting an AMS performance downpipe.
In contrast, one dyno test on a stock BMW 335i N55 registered an average 18 hp and 24 ft-lbs torque increase at the peak.
2. Emission
In a cat-back, you have zero worries about failing emission tests if you stick with the factory cat. Stock exhaust typically comes with two cats to break down toxic exhaust gasses fully.
But if you go for a high-flow aftermarket cat, you’ll still have a controlled emission, although reduced. As long as the test is visual or only uses an OBD2 port, your catted downpipe will likely pass but may fail in front of a sniffer test.
In contrast, a catless downpipe will have zero chance of passing any emission tests, from visual, OBD2, and especially a sniff test. The catless exhaust’s non-compliance with emission regulations is what makes it illegal on public roads.
3. Noise Level
Both catless and catted downpipe will give you a louder and sporty exhaust note. But in terms of noise level, a catless downpipe will register a more aggressive and louder sound than a catback.
This difference in sound level and quality is highly affected by the presence or absence of a catalytic converter, which restricts and dampens the sound flow.
4. Price
A catback exhaust price will range from $300 to $1200. This cost can include the pricing for an aftermarket muffler and tips that are dependent on the materials and brand you’ll choose.
A catless downpipe will be cheaper as it lacks a catalytic converter. It will cost from $150 dollars or more, depending on your product preference.
Which is Better?
Weighing between catless and catted exhaust will lie heavily on the purpose of your mods.
- As discussed, a catless downpipe is used for track-only cars as it gives a better powertrain boost but is illegal on the road due to emission problems.
- On the other hand, a catback mod will suit you well if you’re looking to gain a few more horsepower while remaining emissions-compliant. This is best for a daily driver car that needs a little more power tweak and improved visual and sound aesthetics.
- Ultimately, a cat-back exhaust will increase power without limiting your car to use track-only. Besides, aftermarket exhaust is not the only performance mods you can bank on to improve power. There’s a custom intake, header, and engine tuning, to name a few.
Thoughts on catback exhaust and catless downpipe?
byu/jamesrsg15 inFocusST
Conclusion
The debate between catback vs catless remains a hot topic among car enthusiasts. Your decision to go either way should anchor on knowing what you and your car need and how these mods will benefit you.
Remember that an exhaust mod is but another performance modification you can do. If you are really into power increase, try looking at other mods and perhaps invest in them as well.
Working with Vernon and Ryley has been a great experience for me. Together with the rest of the team, I hope to create reliable and useful information for our readers, no matter where they are and their experience with car maintenance.
