HKS 31006-KH001 Hi-Power Cat-Back Exhaust for 2023+ Honda Civic Type-R FL5 K20C

Vehicle Fitment

• 2023+ Honda Civic Type-R (FL5, FWD, K20C 2.0L Turbocharged DOHC I4)

Fitment Notes

• Direct bolt-on installation - no cutting, welding, or vehicle modification required; all stock rubber exhaust hangers are reused
• This system is valveless - the FL5's OEM exhaust uses an electronically controlled valve that will trigger an error code if removed or left disconnected; the supplied HKS actuator must be installed with the stock valve motor to prevent error codes
• The check engine lamp will not illuminate from this system, but error codes may be visible via OBD diagnostic scanner; the included actuator prevents these codes from being set
• Stock rear undercover must be reinstalled after fitment; minimum clearance between tailpipe and rear bumper should be confirmed at approximately 14mm
• Note on power gains: the stock FL5 ECU manages engine output based on torque targets - exhaust replacement alone will not unlock the full power increase; ECU remapping is required to fully realize the 30% exhaust pressure reduction advantage

Features

• Full straight-pipe, valveless design eliminates flow restrictions - achieves 30% lower exhaust back pressure compared to the factory system
• 74.7mm main pipe transitioning to dual 60.5mm exits - free-flowing path optimized for the K20C's turbocharged output characteristics
• Bullet-shaped silencer design emphasizes both bass and treble frequency ranges simultaneously - delivering a more aggressive, full-spectrum exhaust note than the factory valve-equipped system
• Sound level increased by 13dB over stock and 9dB over the HKS LEGAMAX Sports (31021-AH005) - the most aggressive HKS FL5 exhaust option in the current lineup
• 119mm titanium-finish tail tip with HKS logo - triple-exit rear aesthetic matching the FL5's factory rear bumper opening layout
• Dedicated HKS actuator included - accepts the stock valve motor and replicates OEM valve movement, fully preventing the error codes triggered by a valveless exhaust on the FL5
• Power output exceeds stock from 5,000 to 6,000 rpm, with a measured peak increase of 3.6kW; torque increases up to 7.5 Nm at approximately 3,000 rpm and surpasses stock from 5,000 to 6,000 rpm
• Dual-material construction: SUH409 stainless steel for internal/hidden piping; SUS304 stainless steel for the tip and visible silencer sections

Specifications

• Muffler Style: Hi-Power (valveless, bullet silencer)
• Main Material: SUH409 Stainless Steel (piping) / SUS304 Stainless Steel (tip and silencer)
• Tip Finish: Titanium with HKS Logo
• Tip OD: 119mm
• Main Pipe Diameter: 74.7mm → 60.5mm x 2 (dual exit)
• Sound Level (Near Exhaust): ~93dB (OEM: ~80dB) - +13dB vs stock
• Sound Level (Idle): ~75dB
• Exhaust Back Pressure Reduction: ~30% vs stock
• Peak Power Increase: +3.6kW (5,000-6,000 rpm, HKS in-house measurement)
• Peak Torque Increase: +7.5 Nm (~3,000 rpm, HKS in-house measurement)
• Road Clearance: 125mm (from factory front under panel, stock suspension)
• Compatible Engine: K20C 2.0L Turbocharged DOHC I4
• Drive: FWD

Included Components

• 1x Main muffler with 119mm titanium-finish tip
• 1x #1 Mid pipe
• 1x #2 Mid pipe
• 1x HKS actuator (for stock valve motor - prevents error codes)
• Hook assemblies (left and right)
• Ring gaskets (D60 and D75)
• 3-hole gasket
• Mounting hardware (M10 bolts, nuts, spring washers, flat washers)

Product Description

The HKS 31006-KH001 Hi-Power Muffler is a cat-back exhaust system designed specifically for the 2023+ Honda Civic Type-R (FL5). It represents the most aggressive exhaust option in HKS's current FL5 lineup - producing 13dB more sound pressure than the factory system and 9dB more than the HKS LEGAMAX Sports - through a fully valveless, straight-pipe design built around a bullet-shaped silencer that expands both the bass and treble frequency response simultaneously.

The FL5's factory exhaust uses an electronically controlled valve motor that logs an error code if the valve is removed or disconnected. HKS addresses this directly by including a dedicated actuator that accepts the stock valve motor and replicates its movement, ensuring no error codes are generated during normal operation. The 74.7mm main pipe and full straight-through routing reduce exhaust back pressure by approximately 30% compared to stock - translating to measured gains of up to 3.6kW and 7.5 Nm, with the system outperforming stock from 5,000 to 6,000 rpm. FL5 owners looking to fully capitalize on the improved exhaust flow should combine this system with an ECU remap, as the stock ECU manages output on a torque-based target that limits gains from exhaust alone.