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 or Catless?

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.

The Pros:

• Massive Power Gains: You still eliminate the bottleneck in the massive factory. 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).

• Refined Sound: It dramatically increases the volume and tone of your exhaust but keeps the raspy, ear-piercing frequencies in check.

• No Fuel Smell: The catalytic converter does its job, keeping your garage and your clothes from smelling like a gas station.

The Cons:

• Price: High-flow catalytic cores require precious metals (like rhodium and palladium), making these downpipes more of an investment.

• Still Requires a Tune (Usually): While some ultra-premium catted downpipes guarantee no CEL, most will still eventually throw a code and require a tune to maximize the hardware.