Catted vs. Catless Downpipes: Performance Gains, Sound, and What You Need to Know
You’ve installed a beautiful aftermarket exhaust, the car sounds incredible, but you’re still craving more. More turbo spool, more aggressive sound, and most importantly, more power. If you’re driving a modern turbocharged car—whether it’s housing a BMW S58, a Toyota B58, or an AMG V8—the next logical step in your build is upgrading the downpipe.
But as soon as you start shopping, you’re hit with the ultimate debate: catted vs catless downpipes?
Upgrading your downpipe is the gateway to "Stage 2" power levels, but making the wrong choice can leave you with either a car that's too obnoxious to daily drive or one that leaves horsepower on the table. Here is everything you need to know to make the right choice for your build.
What Exactly Does a Downpipe Do?
In a turbocharged engine, the downpipe is the section of exhaust tubing that bolts directly to the turbine housing of your turbocharger and connects to the rest of your exhaust system.
From the factory, automakers install incredibly dense catalytic converters right in this downpipe to meet strict emissions standards. Imagine trying to sprint while breathing through a thick wool blanket—that’s what your turbo is doing. Factory cats create immense backpressure, trapping heat against the turbo and choking top-end horsepower.
High-Flow Catted Downpipes: The Street-Smart Brawler
If you daily drive your car or want massive performance gains without the aggressive side effects, a high-flow catted downpipe is the premium choice. Instead of a dense 600-cell or 800-cell factory cat, aftermarket catted downpipes typically use performance-oriented 200-cell or 300-cell metallic cores, also known as a high-flow cat.
The Pros:
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Massive Power Gains: You still eliminate the bottleneck in the factory catalytic converter.
A high-quality 200-cell cat flows so well that the horsepower difference between it and a catless pipe is almost negligible on a street car (often just a 5-10 hp difference).
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Refined Sound: It dramatically increases the volume and tone of your exhaust but keeps the raspy, ear-piercing frequencies in check.
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Less Smell: The catalytic converter does its job, helping reduce the strong fuel smell that a catless downpipe can produce in a garage or at idle.
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Better Daily Use: For many drivers, a high-flow catted downpipe is the best balance of performance, sound, and livability.
The Cons:
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Price: High-flow catalytic cores require precious metals (like rhodium and palladium), making these downpipes more of an investment.
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Still May Need a Tune: While some ultra-premium catted downpipes are designed to reduce check-engine lights, most will still benefit from tuning to maximize the hardware.
Catless Downpipes: Maximum Flow, Maximum Trade-Offs
A catless downpipe removes the catalytic converter entirely, which gives exhaust gases the straightest path out of the turbo. That usually means the least restriction, the sharpest turbo response, and the potential for more power than a catted downpipe—though the difference is often small on many street builds.
The trade-off is just as real: catless setups are louder, smellier, and much more likely to be illegal for street use in the United States. They can also produce a harsher tone that some drivers find too aggressive for daily driving.
catted vs catless downpipe: Which One Is Better?
If you want the best all-around setup for a street car, a catted downpipe is usually the smarter choice. It keeps the car more refined, reduces exhaust smell, and still delivers strong gains in power and sound.
If your priority is maximum exhaust flow and you care less about smell, legality, or noise, a catless downpipe may be the better option for track-focused builds.
Is a catted downpipe worth it?
Yes, for most enthusiasts it is. A high-flow catted downpipe delivers a strong blend of performance, sound, and daily drivability without the major compromises of a catless setup.
Is a catted downpipe illegal?
It depends on your state and local emissions laws. In the U.S., replacing or removing the catalytic converter can make a car illegal for street use in many situations, so always check your local regulations before buying.