HKS Header Back Exhaust System - 2013+ FR-S / BRZ / 86

Header Back Exhaust System for the 2013+ FR-S, BRZ, and 86

The HKS Header Back Exhaust System for the 2013+ Scion FR-S, Subaru BRZ, and Toyota 86 is a complete exhaust replacement from the header flange back, covering the full exhaust path between the header and the tailpipe. The header-back designation means this system replaces everything. The front pipe, the catalytic converter section, the midpipe, and the muffler, as a matched, engineered unit. This is the appropriate choice for builds that are also upgrading the headers, ensuring the complete exhaust path is optimized rather than mixing factory and aftermarket sections.

Specs & Highlights

• Header-back exhaust system
• Replaces complete exhaust path from header flange to tailpipe
• Matched engineering throughout: no mixing factory and aftermarket sections
• Optimized for use with aftermarket equal length headers
• Stainless steel construction
• Fitment: 2013+ Scion FR-S / Subaru BRZ / Toyota 86

50.8mm Throughout, Mandrel-Bent Stainless Front Pipe

The header-back system uses 50.8mm (2 inch) diameter main pipe, the same as the SPEC-L2 cat-back, ensuring consistent flow area throughout the system when combined with the HKS equal length headers. The front pipe section is mandrel-bent stainless steel with a flex joint section to accommodate engine movement without creating a rigid joint at the header flange connection. Total system weight from header flange to tip is approximately 11.5 kg, versus approximately 15 kg for the complete factory exhaust from header flange back.

Why the Header-Back Scope Matters for Paired Builds

A header-back system is the correct approach when you are already upgrading the headers. Running an aftermarket header into a stock cat and midpipe means you have an optimized flow area going into a restricted one. The improvement from the header is partially lost at the factory restriction downstream. The HKS header-back system ensures the flow path is consistent and engineered as a complete unit.

Complete the System: Pair with Equal Length Headers

The HKS33005-AT006 Equal Length Catted Header pairs naturally with this system for a complete header-back build. Together they constitute the full front-to-rear exhaust upgrade for the FA20 platform in HKS's parts catalog.

The FT Breakdown

The header-back exhaust is the complete exhaust solution for performance FA20 builds. It is more involved than a cat-back swap but the results reflect the more complete scope of the upgrade. If you are running equal length headers, a cat-back exhaust is leaving performance on the table by keeping the factory front pipe and cat. Pairing the header-back system with the HKS equal length headers (AT006) and the 50.8mm pipe throughout creates an exhaust system with consistent bore size from primary collector to tip — no flow transitions, no mismatched flanges. That complete-system consistency is what the best FA20 exhaust builds look like, and HKS designed the AT001 to complete that picture.