HARDmotion Hyper-Flow Catless Downpipe 2012–2015 Honda Civic Si / 2013–2015 Acura ILX (4.5" Bellmouth )

Built for enthusiasts who want more from Honda's 2.4L platform, Hyper-Flow combines a large exhaust entry, a catless flow path, precision TIG welds, and a satin stainless-steel finish. The assembly is designed for direct bolt-on installation on the specified applications, without cutting or fabrication.

Engineered Around a 4.50-Inch Cast Bellmouth

The bellmouth is the heart of Hyper-Flow. Its oversized 4.50-inch opening provides a generous entry at the engine's exhaust outlet, followed by a transition into the downpipe tubing. Mandrel bends maintain the tube's cross section through the curves, while the 3-inch outlet carries exhaust toward the rest of your system.

The result is an exhaust layout designed to reduce restriction and support engine breathing throughout the RPM range. For a K24 build with the right supporting modifications and calibration, that means more room to develop torque, throttle response, and high-RPM power.

Performance Features

• 4.50-inch oversized cast bellmouth: a large entry designed for K24 exhaust flow.
• 3-inch exhaust outlet: a high-flow connection to the downstream exhaust system.
• Catless construction: removes the catalytic-converter restriction for competition applications.
• Mandrel-bent tubing: maintains a consistent tube profile through each bend.
• Stainless-steel assembly: satin surface finish with precision TIG-welded connections.
• Braided flex section: accommodates movement within the exhaust assembly.
• Dual oxygen-sensor bungs: sensor provisions located on the bellmouth.
• Direct bolt-on design: application-specific flanges and mounting provisions.
• Tuning compatibility: pair with an appropriate ECU calibration to optimize your combination.

Unlock More Power with Hondata FlashPro

Give your tuner the control to match the calibration to your exhaust upgrade. Hondata FlashPro supports tuning and datalogging for the 2012–2015 Civic Si and the applicable 2013+ ILX 2.4L ECU family. Build the hardware and calibration together for a more complete performance package.

On the HARDmotion FlashPro listing, select the 2012–2015 Honda Civic Si application, FP-2012SI-US, and confirm ECU compatibility before ordering. Acura ILX customers should confirm their ECU/application with HARDmotion.

Shop Hondata FlashPro at HARDmotion

Vehicle Fitment

2012–2015 Honda Civic Si | 2.4L K24Z7

• 2012 Honda Civic Si Coupe / Sedan
• 2013 Honda Civic Si Coupe / Sedan
• 2014 Honda Civic Si Coupe / Sedan
• 2015 Honda Civic Si Coupe / Sedan

2013–2015 Acura ILX | 2.4L / 6-Speed Manual

• 2013 Acura ILX 2.4L
• 2014 Acura ILX 2.4L
• 2015 Acura ILX 2.4L

Application exclusions: Not intended for Civic 1.8L models, ILX 2.0L or hybrid models, or the 2016+ ILX 2.4L with an 8-speed dual-clutch transmission. Confirm exhaust connection and sensor compatibility with your existing setup before installation.

Stainless Construction. TIG-Welded Craftsmanship.

Hyper-Flow pairs satin stainless-steel tubing with precise welded connections, application-specific mounting brackets, sensor provisions, and a braided flex section. The finish keeps the assembly clean and understated, while the welds and casting put the construction on display.

For auxiliary wideband monitoring, have your installer confirm sensor thread, clearance, placement, and whether an additional bung is required. The two existing sensor provisions should not be assumed to provide a spare port.

HARDmotion: Honda Acura Racing Development

HARDmotion is focused on the Honda and Acura performance community. Hyper-Flow brings that focus to a purpose-built exhaust upgrade for the ninth-generation Civic Si and the matching ILX 2.4L platform.

Why Buy From HARDmotion?

• Buy directly from the HARDmotion brand.
• Find complementary Honda and Acura performance parts in one place.
• Pair your exhaust upgrade with the correct Hondata FlashPro application.
• Contact the HARDmotion team for application and product questions.

Product Specifications