HKS 31021-BH001 for LEGAMAX Premium FC3/L15B

Vehicle Fitment

• 2016-2020 Honda Civic Coupe (FC3 platform - L15B 1.5L turbocharged, FWD - all trims including LX, Sport, EX, EX-T, EX-L, Touring)

Fitment Notes

• Fits the Honda Civic Coupe (FC3) only - does NOT fit the Civic Sedan (FC1), Civic Hatchback (FK7), or Civic Type R (FK8). The FK7 Hatchback (L15B) uses HKS 31021-BH002 / 31021-AH004; the FK8 Type R (K20C1) uses HKS 31021-BH003
• The Honda Civic Coupe (FC3) was discontinued after the 2020 model year in the US market - this exhaust is specific to the 10th-generation two-door coupe body style
• All L15B 1.5L turbocharged Civic Coupe trims are compatible - confirms fitment does not vary by trim for this exhaust
• Emissions equipment is maintained completely intact - no alterations, replacements, or modifications to catalytic converter or oxygen sensors; suitable for emissions-compliant street use
• Direct bolt-on installation - designed to connect to the OEM catalytic converter outlet with no cutting or welding required

Features

• Legamax Premium muffler design - vehicle-specific application engineering ensures each tailpipe tip configuration is studied from multiple design perspectives to achieve a balanced, high-quality visual focal point that complements the FC3 Coupe's rear styling without appearing generic or oversized
• Dual 3.0" (76mm) polished stainless tips, left and right - transforms the stock hidden-tip appearance of the FC3 Coupe into a distinctly sporty quad-tip rear exit layout
• 2.36" (60mm) dual center pipe routing - increased diameter over the restrictive OEM piping reduces exhaust back-pressure for improved turbocharged engine response and power delivery across the RPM range
• Full straight-through internal structure - the internal pipe layout of the silencer is engineered for efficient gas flow with minimal restriction, contributing to exhaust pressure reduction
• JASMA certified - meets Japan Automobile Sports Muffler Association sound and performance standards, confirming the exhaust delivers a tuned sound level without exceeding regulated noise thresholds
• Advantex glass wool packing - Advantex (fiberglass-type) acoustic packing is used inside the muffler body, chosen for its proven resistance to heat degradation, moisture, and compaction compared to standard steel wool, maintaining consistent sound quality over the life of the exhaust
• SUS304 grade stainless steel construction - provides high corrosion resistance, excellent heat tolerance, and a high-lustre polished finish that resists discoloration and pitting in all weather conditions
• Tip design is vehicle-specific to the FC3 Coupe - HKS studies each base vehicle model to select the tip specification that best balances visual impact with proportional integration into the vehicle's rear fascia design
• Emissions compliant - does not require removal or modification of catalytic converter or emissions sensors
• Engineered and manufactured in Japan by HKS

Specifications

• Part Number: 31021-BH001
• Series: Legamax Premium
• Exhaust Type: Cat-back
• Compatible Platform: Honda Civic Coupe FC3
• Compatible Engine: L15B 1.5L turbocharged inline-4
• Main Material: SUS304 stainless steel
• Center Pipe Diameter: 2.36" (60mm) x 2
• Tip Outer Diameter: 3.0" (76mm) x 2 (left and right)
• Exit Configuration: Dual tips, quad rear exit appearance
• Internal Structure: Full straight through
• Packing Material: Advantex glass wool
• Sound Certification: JASMA certified
• Emissions: All emissions equipment maintained intact
• Country of Manufacture: Japan
• UPC: 4957266923634

Included Components

• 1x HKS Legamax Premium cat-back exhaust assembly (pipes, muffler, tips)
• Mounting hardware and gaskets

Product Description

The HKS 31021-BH001 Legamax Premium is a vehicle-specific cat-back exhaust system for the 2016-2020 Honda Civic Coupe (FC3) equipped with the L15B 1.5L turbocharged engine. HKS developed the Legamax Premium as a premium-tier exhaust line that simultaneously delivers measurable performance gains and a class-appropriate sound character - louder and more distinctive than stock, but tuned to avoid the harshness and cabin drone that compromise daily drivability. The system uses 2.36" (60mm) dual center piping in a full straight-through internal configuration to reduce exhaust back-pressure compared to the restrictive OEM piping, which allows the L15B's turbocharger to spool more freely and improves throttle response and power delivery across the RPM band.

The tailpipe treatment is a defining characteristic of the Legamax Premium line: rather than applying a generic tip to a common platform, HKS engineers study each specific model's rear fascia geometry and design language to select a tip specification that creates a visual focal point while remaining proportionally balanced with the car's overall appearance. On the FC3 Coupe, this results in dual 3.0" polished stainless tips on each side - a quad-exit layout that sharply contrasts with the stock Coupe's largely hidden exhaust tips and adds an unmistakably sporty appearance from the rear. The SUS304 stainless steel construction provides corrosion resistance and a high-lustre polished finish that resists discoloration in all weather conditions, while Advantex glass wool packing inside the muffler body maintains consistent, deep sound quality over the life of the system by resisting the heat degradation and compaction that eventually cause the drone and tonal shift common with lower-quality muffler packing materials.

The system is JASMA certified, confirming compliance with Japan Automobile Sports Muffler Association standards for sound level and exhaust performance. All OEM emissions equipment - catalytic converter, oxygen sensors - remains completely intact and unmodified, making this exhaust suitable for street use in emissions-tested markets. This part is specific to the FC3 Coupe body style; the 10th-generation Civic Hatchback (FK7) uses a separate HKS application (31021-BH002 / 31021-AH004), and the FK8 Civic Type R uses a higher-specification system (31021-BH003) matched to its K20C1 engine and more extreme performance tuning targets.