HKS Replacement Pistons

2013–2020 Subaru BRZ / 2013–2016 Scion FR-S / 2017–2020 Toyota 86 FA20 2.1L Stroker Kit

21003-AT003

Overview:

The HKS Replacement Pistons are engineered specifically for the 2.1L FA20 stroker upgrade found in the 2013–2021 Subaru BRZ, 2013–2016 Scion FR-S, and 2017–2020 Toyota 86 models. Designed as a direct replacement for the pistons included in the HKS 21004-AT002 stroker kit, these pistons are intended for use only with the corresponding rods and crankshaft of the HKS 2.1L capacity upgrade.

Built for enthusiasts seeking reliable high-performance upgrades, these pistons support both naturally aspirated and forced induction setups. They offer optimized compression ratios and durability to handle increased power and boost levels, making them ideal for track-focused builds or high-output street applications.

Key Features:

These replacement pistons incorporate advanced design and materials to ensure strength, efficiency, and compatibility with the FA20 engine platform.

• Manufactured from carefully selected, specially forged raw materials for enhanced strength and durability.
• Compression ratio optimized through rigorous strength analysis and testing to accommodate high power and boost levels.
• 3D-designed piston crown tailored to work seamlessly with the stock direct injection system for improved combustion efficiency.
• Short-height piston design reduces skirt overhang, minimizing potential mechanical issues and improving reliability.
• Engineered to reduce friction and weight, enhancing engine response and longevity.
• Compatible with the factory 86mm piston bore, maintaining block strength without requiring boring, honing, or sleeve installation.
• Supports both naturally aspirated and forced induction applications by enabling head gasket replacement as part of the upgrade.

Construction & Design:

The pistons are forged using premium materials selected for their strength and resistance to the stresses of high-performance operation. The short-height design minimizes piston skirt overhang, which can cause wear and reliability issues in high-revving engines. The piston crown features a sophisticated 3D design that complements the FA20’s direct injection system, promoting efficient combustion and power delivery.

By retaining the stock bore size of 86mm, these pistons allow for a cost-effective installation without the need for additional machining such as boring or honing. This approach preserves the structural integrity of the engine block while providing the necessary strength for increased displacement and power.

Installation & Fitment:

This piston kit is intended exclusively as a replacement for the pistons included in the HKS 21004-AT002 2.1L stroker kit. It is not compatible with rods or crankshafts outside of the HKS 2.1L capacity upgrade components. Installation requires professional engine assembly knowledge and should be performed by experienced technicians familiar with FA20 engine modifications.

No additional boring, honing, or sleeve installation is required due to the pistons’ compatibility with the factory 86mm bore, making this a cost-effective upgrade option.

What's Included:

• Set of specially forged replacement pistons designed for the HKS 2.1L FA20 stroker kit

Ideal For:

• Performance enthusiasts upgrading their Subaru BRZ, Scion FR-S, or Toyota 86 with the HKS 2.1L stroker kit
• Builders seeking reliable pistons capable of handling high boost and increased power levels
• Those looking to maintain factory bore size for a cost-effective engine upgrade
• Applications requiring pistons optimized for direct injection and high-performance combustion