Vehicle Fitment

• 2012-2021 Subaru BRZ (FA20D 2.0L Naturally Aspirated H4, D-4S Port & Direct Injection)
• 2012-2021 Toyota 86 / GT86 (FA20D 2.0L Naturally Aspirated H4, D-4S Port & Direct Injection)
• 2012-2021 Scion FR-S (FA20D 2.0L Naturally Aspirated H4, D-4S Port & Direct Injection)

Fitment Notes

• Fits the FA20D (naturally aspirated, D-4S port + direct injection) engine ONLY — uses a 12mm gear set
• Does NOT fit the FA20F (turbocharged WRX) engine — the WRX requires the FA20F-14MM-OPG with a 14mm gear set
• Does NOT fit the FA20E/FA20DIT (turbocharged BRZ/86 swap) engines
• Available in two variants at checkout: No Treatment (standard billet) or MartenWear Treatment (extreme-duty surface hardening) — this listing covers the FA20D-12MM-OPG in both treatment options
• Inner and outer gears are machined and shipped as a matched set — sold as a complete gearset (1 set per unit)
• Made 100% in the USA with US-sourced materials

Features

• Chromoly billet steel construction — approximately 18x stronger than OEM sintered/powdered metal gears (Boundary billet steel approaches 110,000 PSI yield strength vs. ~6,000 PSI for OEM powdered metal)
• Hot quenched from extreme heat and tempered to an indestructible core for maximum toughness throughout the gear body
• ColdFlow surface hardening process applied after machining for a mirror finish with exceptional wear resistance on the standard (No Treatment) variant
• MartenWear Treatment (optional upgrade): a second-stage in-house heat treatment that hardens the exterior surface to Vickers 620-720 (Rockwell C 55-60), proven wear-free at 13,000+ RPM and highly resistant to debris ingestion
• Surface ground gears for the ultimate in dimensional accuracy, fitment, and oil flow efficiency
• Inner and outer gears machined in matched sets for zero tolerance stacking and optimal gerotor meshing
• Race-inspired gerotor design optimized for maximum oil flow and structural strength
• Mirror finish reduces friction and heat generation under sustained high-RPM operation
• Every set hand-inspected, machine-inspected, and hardness-tested, shipped with a Blueprinting Report confirming specs
• Made 100% in the USA at Boundary's Texas facility
• Backed by Boundary's Limited Lifetime Warranty

Specifications

• Part Number: FA20D-12MM-OPG
• Part Type: Billet Oil Pump Gearset (Inner + Outer Gerotor)
• Engine Application: FA20D 2.0L Naturally Aspirated H4 (Subaru BRZ / Toyota 86 / Scion FR-S, 2012-2021)
• Gear Size: 12mm
• Material: Chromoly Billet Steel (US-Sourced)
• Standard Finish: ColdFlow Mirror Surface Hardened
• MartenWear Surface Hardness (optional): Vickers 620-720 / Rockwell C 55-60
• Verified Maximum RPM (MartenWear): 13,000+ RPM (wear-free)
• Package Weight: 1.0 lb.
• Package Dimensions: 8.5 in. x 6.0 in. x 1.0 in.
• Sold: As a matched inner and outer gear set (1 set per unit)
• Includes: Blueprinting Report confirming dimensional and hardness specifications
• Country of Origin: USA

Included Components

• 1x Inner Oil Pump Gear (FA20D 12mm, billet chromoly)
• 1x Outer Oil Pump Gear (FA20D 12mm, billet chromoly, matched to inner gear)
• 1x Blueprinting Report (dimensional and hardness inspection documentation)

Product Description

The Boundary FA20D-12MM-OPG is a billet chromoly oil pump gearset purpose-built for the naturally aspirated FA20D engine found in the Subaru BRZ, Toyota 86/GT86, and Scion FR-S from 2012 through 2021. The FA20D's factory oil pump uses sintered (powdered metal) gears — a cost-efficient OEM manufacturing method that results in a porous, structurally weak gear material with a yield strength of approximately 6,000 PSI. Under the sustained high-RPM operation that the FA20D is frequently subjected to — particularly in motorsport, track day, and forced-induction applications — these OEM gears represent the most vulnerable point in the engine's lubrication system. Boundary's response is a gearset machined from solid chromoly billet steel, hot quenched and core-tempered to a yield strength approaching 110,000 PSI — approximately 18 times stronger than the OEM sintered gear material.

Every FA20D-12MM-OPG set is produced entirely in-house at Boundary's Texas manufacturing facility using US-sourced chromoly billets. The inner and outer gerotor gears are machined as a matched set — a critical manufacturing discipline that eliminates tolerance stacking between gears and ensures optimal oil flow geometry and meshing efficiency that a mismatched pair cannot achieve. After machining, Boundary applies their ColdFlow surface hardening process, bringing the gear surfaces to a mirror finish for reduced friction and improved wear characteristics. The optional MartenWear upgrade adds a second stage of in-house surface heat treatment, hardening the exterior to Vickers 620-720 (Rockwell C 55-60) — a surface that Boundary has validated to be wear-free at 13,000+ RPM and exceptionally resistant to the contaminated oil conditions that can accelerate OEM gear wear. Every completed set is hand-inspected, machine-inspected, and hardness-tested before shipping, accompanied by a Blueprinting Report that confirms all key dimensional and hardness specifications.

This part number is specific to the FA20D naturally aspirated engine — identified by its D-4S combined port and direct injection system — and uses a 12mm gear set. It is not compatible with the FA20F turbocharged engine used in the WRX (2015-2021), which requires a 14mm gearset under part number FA20F-14MM-OPG. Confirm your engine code before ordering. Backed by Boundary's Limited Lifetime Warranty and made 100% in the USA.