The FA20 engine is a distinctive four-cylinder boxer engine that’s been the power source under the hoods of some of Subaru and Toyota’s most engaging vehicles.
Designed through a collaborative effort by Subaru and Toyota, this versatile engine has powered a variety of sports cars known for their balanced performance and driving enjoyment.
The most prominent cars equipped with the FA20 engine are the Subaru BRZ, Toyota 86, and the Scion FR-S. These models share a common enthusiasm for a lightweight, rear-wheel-drive layout, and the FA20 engine contributes significantly to their low center of gravity and high power-to-weight ratio.
Our interest in the FA20 engine stems from its unique attributes and the niche it occupies in the sports car segment.
The engine employs a boxer configuration—where the pistons move horizontally—which results in a distinctive sound and vibration characteristic. This layout also aids in achieving a lower center of gravity, which in turn enhances vehicle stability and handling.
The Subaru BRZ showcases this engine in a naturally aspirated form, prioritizing linear power delivery and high-revving excitement, while in the turbocharged variant found in some Subaru models, it provides a significant increase in power and torque.
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Exploring the FA20 Engine
In our exploration of the FA20 engine, we’ll focus on its design philosophy, the distinct variants available, and the technical specifications that define its performance.
Fundamentals of FA20 Design
The FA20 engine stands out for its unique layout and construction. Originating from the collaboration between Subaru and Toyota, the horizontally opposed configuration, or ‘boxer’ engine, allows for a lower center of gravity, directly benefiting vehicle handling and stability. It features a lightweight aluminum alloy for its block and heads and includes a direct fuel injection system that contributes to its efficiency and power output.
FA20 Variants Comparison
- Naturally Aspirated: Utilized in the Subaru BRZ and Toyota 86, where it’s known as the 4U-GSE.
- Turbocharged (FA20DIT): Used in the Subaru WRX, which provides enhanced performance thanks to its forced induction.
While both derivatives of the FA20 incorporate similar fundamental engineering, the FA20DIT variant boasts a turbocharger, contributing to a significant increase in torque and horsepower. This is especially evident when looking at the substantial peak torque of 257 lb-ft, which the turbocharged version delivers.
Technical Specifications
Here’s a glance at the technical specs of the FA20 engine:
| Specification | Naturally Aspirated FA20 | FA20DIT |
| Displacement | 2.0 L | 2.0 L |
| Bore x Stroke | 86 mm x 86 mm | 86 mm x 86 mm |
| Compression Ratio | 12.5:1 |
10.6:1
|
| Horsepower | 200 HP @ 7,000 RPM | 268 HP @ 5,600 RPM |
| Torque | 151 lb-ft @ 6,400 RPM | 257 lb-ft @ 2,000-5,200 RPM |
Both variants have their combustion chambers equipped with four valves per cylinder and utilize connecting rods designed for their respective power outputs. The naturally aspirated version shines in higher RPM ranges, while the turbocharged FA20DIT excels with low to mid-range torque.
Technical Enhancements and Modifications
The FA20 engine, when subject to technical enhancements and modifications, can demonstrate marked performance improvements. Let’s explore the specifics of turbocharging, optimizing the intake and exhaust systems, and ECU tuning that enthusiasts and experts often apply to this platform.
Turbocharging the FA20
is a common upgrade for FA20 engines to significantly increase power. Enthusiasts typically use a twin-scroll turbocharger to leverage exhaust gas pulsations and reduce turbo lag. This, combined with a robust intercooler, can manage the increased boost pressure, ensuring temperature stays within safe operating limits. These changes necessitate a rework of the factory engine software to handle the altered air and fuel mixtures reliably.
Intake and Exhaust Optimizations
For us to maximize airflow, we often replace the factory intake with a shorter intake manifold designed to minimize restriction. A 4-2-1 exhaust manifold can also be employed to optimize exhaust flow, allowing quicker expulsion of exhaust gases and enhancing engine breathing. The result is a more responsive throttle and a more efficient power delivery. Modifying the exhaust system not only improves performance but also can give the FA20 a more satisfying exhaust note.
ECU Tuning and Aftermarket Upgrades
ECU tuning is paramount to harmonize the engine’s behavior with its new capabilities, particularly following substantial modifications. An aftermarket tune adjusts the factory engine software to optimize fuel maps, ignition timing, and sometimes, variable valve timing controls. Upgraded fuel injectors and a higher-capacity fuel pump are often required to meet the increased fuel demand created by higher boost levels. The goal is to achieve a balance of power, reliability, and efficacy.
Performance and Reliability
In this section, we explore the Subaru FA20’s efficiency and power output, as well as the engine’s long-term durability concerns. We’re focusing on tangible factors like fuel system design and the implications of direct injection technology.
Efficiency and Power Output
The Subaru FA20 engine has gained accolades for its balance of efficiency and performance. Our engine, leveraging direct injection technology, optimizes the fuel delivery process for more power per combustion cycle, leading to a leaner operation and boosted efficiency.
Key Aspects of FA20’s Performance:
- Power Output: The engine is designed to provide a high power-to-weight ratio, offering a spirited driving experience without excessively compromising fuel economy.
- Fuel Injectors: Direct injection plays a pivotal role in achieving an efficient burn, contributing to the engine’s admirable horsepower figures.
Long-Term Durability Concerns
While the FA20 has strengths, it’s not without reliability concerns.
One issue that we’ve taken notice of, synonymous with many direct-injected engines, is carbon build-up. This can potentially lead to reduced engine performance or even engine damage if not addressed appropriately.
Acknowledged Issues and Actions:
| Concern | Manufacturer Action |
| Carbon Build-Up | Technical Service Bulletins, Advisories |
| Fuel Pump Failures | Recalls and Warranty Extensions |
It’s crucial to keep abreast of these concerns to ensure longevity and reliability in the engine’s lifespan.
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