HKS 31006-BH002 Hi-Power Cat-Back Exhaust for 2017-2020 Honda Civic Si (FC)

Vehicle Fitment

• 2017-2020 Honda Civic Si Sedan (FC, L15B-turbo engine)

Features

• Premium SUS304 stainless-steel muffler and tip for corrosion resistance and durability
• Straight-through "Hi-Power" muffler design with minimal bends for improved exhaust flow
• 65 mm center-pipe (main section) for reduced back-pressure and enhanced power delivery
• Dual 97 mm exhaust tips for aggressive sporty appearance and deeper exhaust tone
• Direct-bolt-on installation with OEM hangers - plug-and-play for Civic Si (2017-2020)
• Includes all necessary gaskets, clamps, and hardware for installation (mid-pipe, muffler, gaskets, bolts, etc.) :contentReference[oaicite:1]{index=1}
• Produces a full, sporty exhaust note while maintaining manageable vibration and throttle response for street use :contentReference[oaicite:2]{index=2}
• Optimized design to improve exhaust scavenging - can lead to improved throttle response and modest gains over stock exhaust flow characteristics :contentReference[oaicite:3]{index=3}

Specifications

• Part Number: 31006-BH002
• Muffler / Exhaust Type: Cat-back exhaust (Hi-Power muffler)
• Muffler Material: SUS304 stainless steel (muffler body & tip) :contentReference[oaicite:4]{index=4}
• Center-pipe (main section) diameter: 65 mm (with some configurations listing 60 mm for parts of the system) :contentReference[oaicite:5]{index=5}
• Tip diameter: Dual 97 mm tips :contentReference[oaicite:6]{index=6}
• System weight (approx): 19.0 kg (per manufacturer spec for Civic Si fitment) :contentReference[oaicite:7]{index=7}
• Exhaust idle noise level: ~92 dB (vs stock ~81 dB) - note: measured at idle, may vary with environment and ECU/fuel trims :contentReference[oaicite:8]{index=8}
• Minimum road clearance (stock suspension): ~115 mm - important if your vehicle is lowered or uses aftermarket suspension :contentReference[oaicite:9]{index=9}

Included Components

• 1x Mid-pipe section (front piece)
• 1x Mid-pipe section (rear piece)
• 1x Hi-Power muffler assembly (with dual 97 mm exhaust tip)
• 1x Gasket (phi62 flange)
• 1x Ring Gasket (phi65 flange)
• Mounting hardware: bolts, washers, nuts for installation
• Sleeve clamp, factory-style rubber stays / hangers (re-uses some OEM hanger points) :contentReference[oaicite:10]{index=10}

Product Description

The HKS 31006-BH002 Hi-Power Cat-Back Exhaust transforms your 2017-2020 Honda Civic Si Sedan's stock exhaust into a performance-oriented, high-flow system that blends sporty sound, improved flow, and OEM-style fitment. Thanks to its straight-through muffler design, 65 mm main pipe and SUS304 stainless construction, the system greatly reduces exhaust restrictions - improving exhaust scavenging, throttle response, and delivering a deeper, more aggressive exhaust note without being overly harsh for daily driving.

Installation is straightforward: the kit bolts directly onto the stock flange and reuses OEM hanger points, minimizing modifications. With dual 97 mm tips and polished stainless finish, 31006-BH002 enhances rear-end aesthetics while delivering a classic J-spec exhaust growl. For Civic Si owners building a spirited street or track-oriented car - especially those with mild tuning or want a more responsive exhaust - this Hi-Power exhaust is a popular and proven upgrade.