Top 7 Best 9th-Gen Civic Si Mods

The 9th-gen Civic Si is one of the most fun-to-drive compact sedans Honda has ever produced. With a rev-happy 2.4L i-VTEC engine, a slick-shifting 6-speed manual, and Honda’s legendary reliability, it’s no surprise that the 2012–2015 Civic Si has become a favorite among tuners and weekend warriors alike.

But, answer us honestly: Is stock enough? If you’re here, you’re probably looking for the best 9th-gen Civic Si mods to wake your car up, improve response, and take your driving experience to the next level. We’ve got you covered. Below are the top seven performance upgrades for those who want to go all-in.

The 7 Best Mods for the 9th-Gen Civic Si

1. Exhaust Upgrade

Upgrading your exhaust is one of the easiest, most affordable, and most rewarding mods you can make to your Civic Si. A high-quality cat-back exhaust system improves exhaust flow, reduces backpressure, and gives your Si an awesome, aggressive tone. It can also increase horsepower, torque, and throttle response when paired with a proper tune.

The Invidia N1 Catback Exhaust System is a go-to choice. With a 76mm stainless steel pipe and titanium tip, it balances performance with daily-drivable sound. Expect strong mid-to-top-end power gains and a deeper, louder tone that doesn’t drone.

2. ECU Tuning

If you’re still on a stock tune, you’re leaving some potential performance on the table. The KTuner ECU Flash unlocks the full potential of the Si’s 2.4L engine with gains of up to +16 horsepower and +8 lb-ft of torque. It sharpens throttle response, eliminates rev hang, and improves low-and midrange torque, reshaping how your car behaves.

Best of all, the KTuner allows you to switch back to stock at any time and offers room for custom tuning as you add more bolt-ons or pursue forced induction down the line.

3. Cold Air Intake

A cold air performance intake allows your engine to breathe better. It increases airflow and improves combustion efficiency while also creating a deeper sound from the engine bay. The Skunk2 Cold Air Intake is specifically designed for the 9th-gen Civic Si, using a molded polymer tube rather than aluminum in the name of better heat insulation. Cooler airflow nets you more power.

It also offers excellent fitment and positions the filter for improved ground clearance over some other kits, which is a nice touch for those worried about daily driving in bad weather.

4. Short Shifter Assembly

The factory shifter isn’t bad. After all, most performance Honda transmissions are excellent. But if you want a race-car feel every time you change gears, an aftermarket shifter assembly is a must. The Hybrid Racing Shifter cuts down shift throw by up to 50%, reduces gate spacing, and gives you a much tighter, more precise feel from gear to gear.

But remember that it’s not just about faster shifts. A short shifter is about enjoying every gear change, and the Hybrid Racing Shifter is a great choice.

5. Clutch Release System

Upgrading your clutch master and slave cylinders can drastically improve your shifting feel, especially at high RPMs. The Hybrid Racing Clutch Release System replaces weak factory components with durable, high-performance parts, giving you a more direct pedal feel and helping eliminate missed shifts.

This mod isn’t flashy and only you’ll know you did it, but you’ll notice the difference every time you row through the gears, especially with a tuned ECU and short shifter.

6. Forced Induction Kit

Want a real boost? A forced induction kit – like a turbocharger or supercharger setup – can turn your Si into a torque-happy monster. While the 9th-gen’s engine isn’t factory-boosted, the platform has a stout bottom end and is well-known for handling forced induction with the right supporting mods and tuning.

If you’re going this route, you’ll need a complete kit, an upgraded fuel system, and serious tuning, but the payoff is massive gains in power and overall performance in a car that doesn’t weigh that much.

7. Handling Upgrades

What good is power if your Civic Si can’t handle corners? Improve your driving feel with a combination of:

• Coilovers for adjustable ride height and damping
• A rear sway bar for flatter cornering and reduced understeer
• A rear motor mount to reduce engine movement and improve traction under throttle

Whether you’re daily driving or hitting canyon roads, these handling upgrades make your Si feel more planted, responsive, and track-ready.

Build the Civic Si You Want

There’s no shortage of 9th-gen Civic Si mods to explore, especially if you’re aiming for full bolt-ons or looking to prep for track days. It’s a great tuner car with plenty of aftermarket support. Whether you want to sharpen your shifts, improve your cornering, or add serious power under the hood, these upgrades are the perfect place to start.