HKS FA20 2.1L Upgrade: Power & Precision

The Subaru FA20 engine, found in popular models like the BRZ and WRX, is renowned for its boxer-twin configuration and engaging driving experience. However, for enthusiasts seeking more power and a more potent performance envelope, the aftermarket offers a variety of upgrades. Among these, the HKS FA20 2.1L capacity upgrade kit stands out as a comprehensive solution for those looking to significantly boost their engine's displacement and, consequently, its output. This article delves into what this kit entails, the feasibility of a novice mechanic undertaking such a project, and the essential components and considerations for a successful engine rebuild.

Understanding the HKS FA20 2.1L Capacity Upgrade Kit

At its core, the HKS FA20 2.1L capacity upgrade kit is designed to increase the engine's displacement from the stock 2.0 litres to 2.1 litres. This increase in displacement is achieved through a combination of carefully engineered components that allow for larger pistons and potentially a revised crankshaft or connecting rods. A larger displacement generally translates to an engine that can inhale and exhale more air and fuel mixture per cycle, leading to an inherent increase in torque and horsepower. HKS, a globally recognised name in automotive performance tuning, is known for its meticulous design and high-quality manufacturing, ensuring that their kits are built for both performance and reliability.

The kit typically includes:

• Oversized Pistons: These are the primary components responsible for the increased displacement. They are precision-machined to higher tolerances and often feature specific crown designs to optimise combustion.
• Forged Connecting Rods: While not always included, stronger connecting rods are often recommended or supplied with such kits to handle the increased stress and power.
• Crankshaft Modifications or Replacement: Depending on the specific kit and intended power output, modifications to the stock crankshaft or a fully forged replacement might be part of the package to accommodate the increased stroke or simply to enhance durability.
• Bearings and Seals: High-performance bearings are crucial for maintaining oil pressure and reducing friction under increased load. New seals are also essential for preventing leaks.
• Gaskets and Hardware: A complete set of high-quality gaskets and necessary hardware, such as head bolts, is vital for a proper seal and secure assembly.

Can a Novice Mechanic Rebuild an FA20 with This Kit?

This is a crucial question for many aspiring tuners. While the desire to enhance one's vehicle is strong, the complexity of modern engines, especially a boxer engine like the FA20, cannot be understated. Rebuilding an engine, particularly one with upgraded components like the HKS 2.1L kit, is a significant undertaking that requires not just mechanical aptitude but also a meticulous approach, patience, and the right tools.

A novice mechanic, defined as someone with limited experience in major engine work, might find this project extremely challenging. The FA20, as noted in enthusiast forums, has specific intricacies. The reliance on precise sealant application, specific torque sequences, and the potential need to "back out" bolts before final torquing are all steps that demand a high level of attention to detail. Mistakes in these areas can lead to catastrophic engine failure.

Factors to Consider for Novices:

• Complexity of the FA20: Unlike simpler inline engines, the boxer layout can sometimes present accessibility challenges. Furthermore, the FA20's specific design features, such as its direct injection system, add layers of complexity.
• Precision Required: Engine building is a science. Tolerances are tight, and any deviation from specifications can have severe consequences. This includes torquing bolts to exact specifications, ensuring proper ring gap, and critical assembly lubrication.
• Tooling: A comprehensive set of specialised tools is essential. This includes, but is not limited to, a high-quality digital torque wrench, engine stand, engine hoist, appropriate socket sets (including 12-point sockets for head bolts), and various gasket removal tools.
• Learning Curve: Even with detailed instructions, the actual hands-on experience of rebuilding an engine involves a steep learning curve. Understanding how parts fit together, identifying potential issues, and knowing how to correct them are skills developed over time.

Recommendation for Novices:

Given these factors, it is generally advisable for a novice mechanic to approach an engine rebuild of this magnitude with caution. Options include:

• Gain More Experience: Start with simpler engine rebuilds or maintenance tasks on less complex engines to build foundational knowledge and skills.
• Seek Professional Guidance: Work alongside an experienced mechanic or consider having a reputable workshop perform the more critical aspects of the rebuild, even if you plan to assist.
• Consider a Pre-Built Short Block: As suggested by some experienced members, purchasing a pre-built, upgraded short block from a reputable tuner like IAG, which often features improved oiling systems (a known Achilles' heel of the FA20), and then assembling the rest of the engine yourself, can be a more manageable approach. This allows you to focus on the familiar components while leveraging the expertise of specialists for the core engine internals.

Essential Components and Considerations for an FA20 Rebuild

Whether you're a seasoned professional or a determined novice, a successful FA20 rebuild, especially with an upgrade kit, requires careful attention to detail and the use of high-quality replacement parts. Based on common practices and recommendations from the Subaru community, here's a breakdown of essential items:

Critical Internal Components:

Ancillary Components and Fluids:

• Full Engine Gasket Kit: Beyond head gaskets, all other seals and gaskets (intake, exhaust, oil pan, etc.) should be replaced.
• Direct Injector Seals: If applicable to your FA20 variant, new seals for direct injectors are often necessary.
• Clutch, Pressure Plate, and Throw-Out Bearing: With the engine out and the transmission potentially needing to be removed, it's an opportune time to replace these wear items, especially if planning a power increase. A new flywheel is also a wise consideration.
• Water Pump: Another component that benefits from replacement while the engine is disassembled to prevent future cooling system issues.
• Spark Plugs: Replace with new plugs, ensuring they are gapped correctly for the new engine configuration.
• Larger Injectors: If the capacity upgrade and subsequent tuning necessitate more fuel delivery, larger capacity fuel injectors will be required.
• Assembly Lube: Essential for lubricating bearings, journals, and cylinder walls during assembly to prevent damage during initial start-up.
• Sealants: High-temperature RTV sealants (e.g., Permatex The Right Stuff, ThreeBond) are critical for specific areas like the oil pan and timing cover. Use the correct type and apply it precisely as per the service manual.
• Loctite: Blue Loctite is typically used on various fasteners to prevent loosening due to vibration.
• Cleaning Supplies: An abundance of brake cleaner, shop towels, and plastic scraping tools are needed for thoroughly cleaning mating surfaces of old gasket material. This is often the most time-consuming part of the process.

Tools Required for the Job

A successful engine rebuild hinges on having the right tools. For the FA20, expect to need:

• Digital Torque Wrench: Accuracy is paramount. A torque wrench with digital readout provides precise measurements.
• Engine Stand: Essential for safely supporting and manipulating the engine during the rebuild.
• Engine Hoist: Necessary for removing and reinstalling the engine into the vehicle.
• Socket and Wrench Set: Including metric sizes (10mm, 12mm, 14mm are common) and a larger size for the crankshaft bolt (often 22mm). 12-point sockets are specifically needed for the cylinder head bolts.
• Piston Ring Compressor: To safely install pistons into the cylinders.
• Micrometers and Calipers: For measuring bearing clearances, piston-to-wall clearance, and other critical dimensions.
• Gasket Scrapers and Sealant Applicators: Plastic scrapers are preferred to avoid damaging aluminium mating surfaces.

Frequently Asked Questions

Q1: What is the primary benefit of the HKS FA20 2.1L upgrade kit?
A1: The primary benefit is an increase in engine displacement from 2.0L to 2.1L, which generally leads to improved torque and horsepower figures across the rev range.

Q2: Is the HKS FA20 2.1L kit suitable for naturally aspirated or forced induction setups?
A2: While the kit increases displacement, its suitability for naturally aspirated (NA) or forced induction (FI) depends on the overall build strategy and supporting modifications. For FI, higher compression pistons might be used, or the kit may be designed with forced induction in mind.

Q3: How much more power can I expect from this kit?
A3: Power gains are highly dependent on supporting modifications (exhaust, intake, tuning, intercooler, etc.) and the specific configuration of the engine. A well-executed NA build might see modest gains, while a forced induction setup could benefit significantly more.

Q4: What is the most challenging aspect of rebuilding an FA20 engine?
A4: Many enthusiasts cite the precise application of sealants, the specific torque sequences for critical fasteners, and the overall cleanliness required during assembly as the most demanding aspects. Ensuring the FA20's oiling system is robust is also a key consideration.

Q5: Should I consider an aftermarket oil pump and pickup with this upgrade?
A5: Yes, given the known vulnerabilities of the stock FA20 oiling system, upgrading the oil pickup tube and potentially the oil pump is highly recommended, especially when increasing power or operating the vehicle in demanding conditions.

Conclusion

The HKS FA20 2.1L capacity upgrade kit offers a compelling pathway to enhanced performance for Subaru owners. It represents a significant mechanical endeavour that demands precision, patience, and a thorough understanding of engine building principles. While the allure of a more powerful engine is strong, a novice mechanic should carefully assess their skills, available resources, and willingness to learn before embarking on such a project. For those who undertake it, meticulous attention to detail, the use of high-quality components, and adherence to factory or specialist specifications will be paramount to achieving a reliable and potent outcome. Consider starting with simpler upgrades or seeking expert guidance to ensure a successful build.