An exhaust upgrade can add power, but how much depends on the engine. On a naturally aspirated engine, a cat-back system usually adds only a small amount, mainly near the top of the rev range, while headers make a bigger difference. On a turbocharged engine, the exhaust before and right after the turbo matters most, so a less restrictive downpipe together with matched engine calibration gives more than a cat-back alone. For most owners, a cat-back’s real benefits are sound, weight and looks.
What each part of the exhaust does
| Section | Effect on power |
|---|---|
| Headers or manifold | Largest effect on naturally aspirated engines; shapes the torque curve |
| Downpipe (turbo engines) | Large effect, since back pressure after the turbo slows spool; needs calibration |
| Mid-pipe and resonator | Small to moderate |
| Cat-back | Small; mostly sound, weight and appearance |
| Axle-back or muffler only | Very small; mostly sound |
Is a cat-back exhaust worth it?
A cat-back is worth it if you want a better sound, lower weight (especially with titanium) and a modest top-end gain without affecting emissions equipment. It is not the right buy if your only goal is a large power increase; see axle-back vs cat-back and cat-back exhaust systems.
Cat-back vs full exhaust
A cat-back replaces everything after the catalytic converters; a full exhaust may also replace headers or the downpipe. Full systems can add more power but are more involved to install, and any change upstream of the converters must keep the emissions equipment and comply with your state’s rules.
What does a downpipe do?
On a turbocharged car, the downpipe connects the turbocharger’s outlet to the rest of the exhaust and, on many modern cars, contains a catalytic converter. A larger, smoother downpipe lets the turbo spool more freely. High-flow versions that retain a catalytic converter are available for many cars; removing the converter from a road vehicle is not legal, and an engine calibration is needed to take advantage of the change.
Does a louder exhaust mean more power?
Not necessarily. Sound comes mostly from the muffler design; a loud system can make the same power as a quieter one. If highway drone is a concern, see exhaust drone.
Measuring the gain
The only reliable way to see a gain is back-to-back dyno runs in the same conditions; see what is a dyno? and horsepower vs torque.
Our cat-back systems
We carry cat-backs for the WRX and STI, BRZ, 86 and GR86, Civic Si and Integra, such as the MAPerformance cat-back for the 2015-2021 WRX/STI ($999.99); see WRX exhaust, BRZ exhaust and Civic Si exhaust.
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