Subaru FA20: Everything You Need To Know

At the start of the year 2012, Toyota and Subaru collaborated on an engine development venture that produced two-way products for both parties. Akin to the FB machines, FA holds the same concept, but the main effort is to reduce the weight while maintaining durability. Hence, reaching the goal and develops it more and more.

Known in the Subaru BRZ, this engine is called the FA20.

Join me as we discuss the engine’s reliability, design, issues, potential, and many more.

Let’s get right to it!

What are Subaru FA20 Engines?

The Subaru FA20 engine is a development project and a joint venture between two of the most recognized automakers out there, Subaru and Toyota. FA20 is a naturally aspirated engine with different versions, including turbocharged releases that were an alternative to the aging EJ engines. To add, the Toyota has the same concept machine in 4U-GSE, which was installed in the Toyota 86 and Scion FR-S; the FA20 Subaru powered the light and sporty coupe Subaru BRZ model.

The FA20 engine has an aluminum cylinder block and heads with four valves per cylinder. The cylinder heads featured several technologies from Toyota, such as the direct fuel injection system Toyota D4S, all while being adorned as part of the Wards’ Auto as one of their “Ten Best Engines” list in 2013.

Subaru engines are designed to use high-octane fuel.

Engine Specifications and Design:

  • Production Run: 2012 – Present
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: Flat-4 (Boxer type)
  • Bore: 86 mm
  • Stroke: 86 mm
  • Valvetrain: DOHC four valves per cylinder
  • Displacement: 2.0 L (1998 cc)
  • Compression Ratio: 10.6 for turbo versions and 12.5
  • Weight: 377 lbs.
  • Maximum HP: 300 HP at 5,600 RPM
  • Maximum Torque: 295 lb-ft at 2,000 – 4,800 RPM

 FA20 D

Inspired by the under square FB20 engine framework, the FA20 is modified into a perfectly square bore/stroke ratio paying homage to the iconic Toyota AE86. A square machine has equal bore and stroke dimensions giving an equal bore/stroke value of exactly 1:1 proportions. It uses a port and direct fuel injection.

FA20 engine has a cylinder bore of 86 mm, piston stroke of 86 mm, and a compression rating of 12.5. FA20 machines are a lot shorter than an average upright inline-4 or V-configuration engines, with the large DOHC cylinder heads sitting very low down in the chassis.

The heads are also equipped with a variable valve timing system AVCS, by Subaru, on both intake and exhaust camshafts. Apart from being a more balanced engine than the FB20, FA20’s engine features a better and restyled bottom, new crankshafts, connecting rods, and pistons. The exhaust system includes a steel 4-2-1 exhaust manifold and is available on this FA20D version.

FA20D can produce 200 HP at 7,000 RPM and 151 lb-ft of torque available at 6,400 – 6,600 RPM.

Applications of FA20 D engine:

  • 2012 – 2016 Subaru BRZ/Toyota GT86 197 HP at 7,000 RPM and 151 lb-ft torque at 6,400 – 6,600 RPM
  • 2017 – 2020 Subaru BRZ/Toyota GT86 205 HP at 7,000 RPM and 156 lb-ft torque at 6,400 RPM

FA20DIT, FA20F, and FA20E

FA20DIT, FA20F, and FA20E are the turbocharged versions of the FA20 engine, which, as we mentioned earlier, came to replace the aging EJ205 and EJ207 engines; an alternative. These engines have Subaru’s own direct fuel injection system; FA20DIT has a Garrett MGT2259S twin-scroll turbocharger with a 15.9 psi maximum boost pressure and a lower compression rating 10.6; a redeveloped head that contributes better airflow and optimized combustion chambers.

Turbo engines have new camshafts with additional functions and a plastic intake manifold with (tumble generator) TGV valves inside. The FA20F was awarded one of the “Ten Best Engines” list by Wards Auto in two consecutive years, 2015 and 2016.

Applications of FA20F, FA20DIT, and FA20E engines:

296 HP at 5,600 RPM and 295 lb-ft of torque at 2,000 – 4,800 RPM

  • 2012 JDM Subaru Legacy 2.0GTDIT
  • 2014 Subaru Levorg
  • 2015 JDM Subaru WRX S4
  • 2014 – 2018 USDM Subaru Forester or Forester XT 250 HP at 5,600 RPM and 258 lb-ft at 2,000 – 4,800 RPM
  • 2014 – 2018 JDM Subaru Forester 276 HP at 5,600 RPM and 258 lb-ft at 2,000 – 5,200 RPM
  • 2015 USDM Subaru WRX 268 HP at 5,600 RPM and 258 lb-ft at 2,000 – 5,200 RPM with Rev Limit at 6,700 RPM.

Engine Tuning, Upgrades, and Modifications

FA20 engines are also excellent platforms for engine tuning and upgrades. You are fortunate if you get your hands on an already turbocharged FA20 like the FA20 DIT because it will be easy for you to increase the engine’s power production. Since you will just need to buy a 3-inch aftermarket cat-back exhaust system, boost controller, cold air intake, and adjust the ECU.

If your car is installed with an automatic transmission, it is better for you to install an aftermarket radiator and a frontal intercooler. That would suffice and enough for active driving, but increasing the power to 400 HP requires a turbo kit for the naturally aspirated one.

Owners of BRZ and GT86 are the ones who needed turbochargers since stock FA20 does not come with it. You need to purchase a straight exhaust system, install a cold air intake, adjust the ECU and gain an additional 20-25 HP. That would be enough, and don’t overbuild your engine with a high rev naturally aspirated because it is expensive. The turbo variants are way faster and more performance-focused.

The wisest choice for the Toyota 86 is a supercharger kit, and install it on the FA20 stock internals. These kits have a maximum boost pressure of 9-10 psi, and that is enough power to kick you in the back and feel the gains at 300 HP at maximum. It is the simplest and the optimum choice to receive great power.

For more than 350 HP gains, you will need a new fuel pump, pulleys, water/methanol injection, fuel injectors, a transmission cooler, and an aftermarket radiator. You can also opt to install a turbo kit based on Garrett GTX3076R instead of the standard supercharger kit. This kit is possible to install on stock internals and gain 400 HP on wheels, even reaching 500 HP using a higher octane fuel.

FA20 stock internals is highly reliable, can withstand larger power production of more than 500 WHP and even 600 HP with the correct fuel and ECU adjustments.

Problems Surrounding FA20 Engines:

Perfect engines don’t exist even the most intricate engineering marvels; there are no exceptions to the rules. The same concept applied to the Subaru FA20, which are competent engines, but there are some issues and problems that we must be informed about, even the most minor portion.

The first issue is the carbon build-up. This problem is more prevalent in the FA20DIT version, the turbocharged one. So why does it affect the FA20DIT only? With direct injection alone, all fuel is directed towards the cylinder. However, engines naturally produce blow-by oils that move through the intake tract. These oil blow-bys eventually make its way to the intake ports and valves where it starts to form carbon deposits. Fuel is sprayed in this particular location with the port injection, so oil deposits are pushed away.

The thing is, once this carbon build-up becomes excessive, the engine would find it hard to breathe and can no longer receive optimal airflow. This happens because the deposits block the airways of the intake ports, making them smaller over time which can lead to more drivability issues. Expect these build up every 60,000 – 100,000 miles.

Next is valve spring failure. This is a more common issue on the naturally aspirated FA20. Subaru and Toyota issued a recall campaign for valve springs of the Subaru BRZ, Toyota 86, and Scion FR-S. Yeah, sure, Subaru fixed the thing after pulling the engines and almost 10 hours of labor. But, there’s more to that, and some owners run into more problems beyond that. There have been reports that techs applied too much sealant, which caused this excess amount to mix with engine oil leading to a few complete engine failures.

Another one is factory tune issues. There are reports that some owners are not happy with the factory engine software or the tune that comes with the car. Some say that it runs roughly, runs too lean, runs too rich, is pretty hard on boosting, and many more. However, this issue is slightly subjective since FA20s run on either direct or direct and port.

The last and certainly pops up around 325-350 torque is the connecting rod linking to an engine problem. Since FA20 engines are easily tuned and modded, some put a ridiculous amount of power. Though the internals is solid and reliable, entering a foreign territory beyond stock power levels is damaging to the internals, most commonly the connecting rods – and this is serious. Anyway, if a rod is bent and knocking starts to happen, you might need to rebuild your FA20 engine.

Summary

The Subaru FA20 engines, apart from being a good platform for tuning and modifications, gained an exemplary reputation as a flat-4 heavyweight that, with the right hands, can end up reaching the heights of 600 HP. Toyota and Subaru joined forces and integrated technologies such as the direct injection system and the AVCS variable valve timing to make the engine more efficient and consume less. Also, this engine has a constant development for its succeeding machines over the years, and progress is relentless. The aftermarket support and items are not hard to come by, which other engines are not known for.

Some troubles might arise to the FA20 engine, such as misfiring, connecting rods issue, and carbon build-ups; some are not satisfied with their ECUs, and they take it as an engine weakness. However, these problems are all part of being a quality engine since they will find a way to make it better.

I hope that this brief and straightforward discussion helped you understand the engine design, architecture, issues, engine potential, reliability, and overall impact on the automotive industry.

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