The FA24 Engine Manual. When Subaru revealed the new 2022 WRX, there was only one question on everyone’s mind: Would it feature the FA24? When the answer was yes, WRX fans celebrated by throwing up their hands. Finally, the FA20DIT from 2015 was receiving a significant improvement.
Subaru first unveiled the FA24 boxer engine in the Subaru Ascent in 2019, to generally positive reviews. They did, however, re-tune the engine for use in the 2022+ WRX, reducing torque while increasing horsepower. Subaru also developed a naturally aspirated variant of the FA24 for use in the 2022+ Subaru BRZ.
Despite the fact that the FA24 is still a new engine, we’ve compiled everything we know about it in this guide. We’ll examine at its history, specifications, design, dependability, and, most significantly, performance below. Let’s get this party started.
*Because the FA24 is almost spanking new, we’re sure to obtain some more information in the future. Check back here for updates on a regular basis.
FA24’s Past
The FA24DIT has only been in production since 2018, when Subaru debuted it. They started with the 2019+ Ascent, then moved on to the 2020+ Outback XT and Legacy XT. Subaru will use it for the first time in the performance-oriented WRX in 2022. The FA24D naturally aspirated version for the Subaru BRZ and Toyota GR86 is also new for 2022.
Initially, it was widely assumed that Subaru will also include a high-performance version of the engine in the 2022 WRX STi. However, Subaru announced earlier this year that the STi would be discontinued for the 2022 model year, shocking many rally fans. Instead, it means that the FA24-powered WRX is now the top performer in Subaru’s lineup.
Subaru typically modifies their WRX engines every 3-4 years, so we are unlikely to see any changes for a time. However, early reviews indicate that the engine is already capable and enjoyable.
Subaru 2.4 L Engine Specifications
The 2.4L Subaru FA24 engine specifications are as follows:
Applications for FA24
The FA24 engine can be found in the following models:
- Subaru Ascent (2019+)
- Subaru Legacy XT 2020+
- Subaru Outback XT 2020+
- Subaru WRX 2022+
- Subaru WRX GT 2022+
- Subaru Levorg 2022+ (Only available in Europe, Asia, New Zealand, and Australia)
Design of the FA24DIT Engine
The FA24, like nearly all other Subarus, is powered by a horizontally opposed “boxer” engine. The FA24DIT is based on the outgoing FA20DIT (FA20F), a 2.0 L engine developed by Subaru in 2012. The FA24 is powered by a 2.4 L turbocharged flat-four engine with direct injection. Subaru expanded the bore from 86mm to 94mm in order to gain 0.4 L over the FA20DIT. It has an all-aluminum block and head, as well as dual overhead cams that are controlled by a timing chain. The compression ratio remains constant from the FA20DIT at 10.6:1, and certain versions include an oil cooler to regulate oil temperatures. The utilization of a twin-scroll turbo is also similar.
Twin-scroll turbos outperform single-scroll turbos in terms of efficiency and performance. The twin-scroll design separates the exhaust gas pulses coming out of the exhaust manifold into two ports, or scrolls, that feed into the compressor wheel separately. This results in a smoother flow of exhaust into the turbo, allowing for improved cam timing and more pulse energy. Subaru’s tune takes advantage of this, along with direct injection, to significantly enhance power output and efficiency on the FA24. It produces a flatter, earlier torque curve while enhancing horsepower throughout the power band.
The FA24D is a naturally aspirated version of the FA24. The FA24D adds port injection to the engine’s direct injection using the Toyota D-4S fuel system. This minimizes carbon buildup while also giving more fuel for peak power. To compensate for the loss of forced induction, the compression ratio on the FA24D has been increased to 12.5:1. Subaru also modified the torque curve in the FA24D to be significantly earlier than in its naturally aspirated predecessor, the FA20D.
Direct Injection of Gasoline
The continuation of direct injection is the most significant carryover from the FA20DIT to the FA24DIT. Gasoline direct injection, or GDI or DI for short, is a relatively new technology developed by Bosch in Germany in the 1950s. Subaru, on the other hand, did not begin to utilise the technology until the 2010s, with the FA and FB series of engines.
GDI fuel systems operate at significantly higher pressure rates than conventional port fuelling systems. High pressure gasoline pumps pressurize fuel at 2,000-3,000 PSI, which is 50 times more than port fuelling systems. Instead of injecting atomized fuel upstream, GDI injects it directly into the combustion chamber. This enables extremely precise fuel injection timing, which significantly cuts emissions while improving fuel efficiency and performance.
The disadvantage of GDI is the significantly greater production costs, as well as the increased complexity of the systems. GDI fuel injectors are significantly more expensive than regular counterparts, and GDI systems include an additional fuel pump. The typical in-tank fuel pump is included, as well as a high-pressure fuel pump located directly upstream of the injectors and fuel rails. Unfortunately, these high pressure fuel pumps have not always been reliable, and they are costly to replace. Furthermore, DI engines are prone to carbon buildup on the intake valves.
FA24 Dependability
Early indications of the FA24’s reliability are promising, but the engine is so new that data is scarce. Nobody has driven the naturally aspirated FA24D, so it’s anyone’s guess what to expect from that engine. However, if the previous FA20s are any indication, there are a few things to keep an eye out for.
The carbon buildup on the intake valves will surely be number one. Carbon accumulates on the intake valves of GDI engines because the placement of the fuel injectors prevents them from spraying gasoline on the back of the intake valves to clear the carbon away. Typically, this is not a major issue, and 95% of owners will never have problems due to excessive carbon buildup. In severe circumstances, it can result in poor idling, misfiring, and power loss. The only way to avoid this is to get your intake valves cleaned on a regular basis using a process known as walnut blasting. However, these issues are highly unlikely to affect the average driver, as they rarely caused serious problems in previous GDI Subarus.
Another concern with the current FA20DIT is faulty connecting rods. Early 2015-2016 WRXs with modified engines were known for throwing rods at little mileage. The FA24, on the other hand, is said to have improved piston design and stronger connecting rods, which should presumably alleviate any remaining concerns.
Aside from those, there have been no widespread reports of FA24 engine problems. That may change now that it is being pushed to its performance limits.
FA24DIT Performance and Improvements
Now for the most interesting aspect of the FA24DIT: performance and modifications. Depending on the application, the FA24 produces 260-271 horsepower and 258-277 tq from the manufacturer. It achieves peak torque as early as 2,000 RPM and has a red line of 6,100 RPM, which is 600 RPM lower than its predecessor. Depending on the BRZ options, the normally aspirated FA24D produces 228-234 horsepower and 184 tq. The BRZ produces torque at 3,700 RPMs, but it lasts till red line.
On the track, the FA20DIT accelerates from 0 to 60 mph in 5.5 seconds, while its normally aspirated sibling takes 5.9 seconds. The FA20DIT is also faster at the 14 mile, clocking it at 13.9 seconds at 103 mph. The BRZ, on the other hand, finishes it in 14.3 seconds at 98 mph. The FA24 only uses 12 PSI of boost, which is 4 PSI less than the FA20, yet it produces nearly comparable power. The FA24 is substantially more responsive and forceful off boost than its predecessor, because to its bigger displacement.
One of the most common complaints about the new FA24 is that it isn’t any more powerful than its predecessor, and that argument has some merit. The torque output is the same, however the horsepower is only raised by 3. According to several dynos, the FA24 produces fewer horsepower than the FA20. While the peak numbers may not be flattering for the 2.4 L, the entire powerband has been greatly improved. The FA20’s terrible torque dips and inconsistent power distribution are no longer an issue. The new engine expands the car’s mid-range and allows it to attain peak torque earlier and keep it for longer.
Related : The EJ257 against FA20DIT
FA24 Improvements
Unfortunately, neither variant of the FA24 has a lot of aftermarket support as of yet. It is unknown whether FA20 WRX parts will fit the new engine, but they are unlikely to be direct fits. With the new FA24s, it appears that the industry will have to start from scratch, as there is no well-known tuning option.
However, we do know a little bit about the FA24’s power limits. As part of a massive build, Prime Motoring installed an FA24 engine from an Ascent into a Subaru Crosstrek. It made around 500whp on the stock block and has allegedly held up well without serious difficulties. While it’s a stretch to say the FA24 is now capable of consistently producing 500whp, it does show that these motors can withstand some future modifications and abuse.
FA24 Engine Overview
The FA24 engine is still in its early stages, but it appears to be a fantastic motor thus far. It has already demonstrated some major potential in terms of performance, and it is no slouch in its stock forms. The combination of direct injection, a twin-scroll turbo, and greater displacement will undoubtedly make the FA24 competitive in the near future.
Much is unclear about the FA24, and there is essentially no aftermarket support – for the time being. But, as we’ve seen the Subaru community do time and again, it’s only a matter of time before someone cracks the code. It’ll be interesting to see how the FA24DIT ages alongside the WRX and how the Subaru community evolves alongside it.
