FA24 Engine Reliability: Complete Guide for WRX Owners
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FA24 engine reliability is well-regarded because the motor uses a robust semi-closed deck block design that resists cylinder wall flex far better than the open-deck FA20 it replaced. Factory internals comfortably handle 350-400 wheel horsepower with proper supporting modifications before the stock block needs upgrading. Known concerns include excess RTV sealant in the oil pickup tube and a plastic charge pipe that can blow off under higher boost, but both have straightforward fixes. With routine maintenance and targeted modifications like an air-oil separator and upgraded charge pipe. The FA24 delivers dependable daily power that the Subaru community is only beginning to fully explore. Crawford Performance offers built FA24 short blocks and long blocks for owners ready to push well beyond stock limits.
FA24 Engine Specifications and Design
The FA24 engine marks a major shift in how Subaru builds performance powerplants. This 2.4-liter horizontally opposed boxer four-cylinder motor features a cylinder bore of 94 mm and a piston stroke of 86 mm. Which creates a total displacement of 2,387 cc. Unlike older Subaru motors that used a square or long-stroke design, the larger bore of this block allows for larger valves and improved airflow. This design helps the turbocharged variant (the FA24DIT found in the 2022 and newer WRX) produce 271 horsepower at 5,600 rpm and a broad torque curve of 258 to 277 pound-feet of torque that peaks from 2,000 to 4,800 rpm. To learn more about how this motor behaves in real-world driving, you can read our guide on FA24 reliability modifications for street builds.
A Stronger Semi-Closed Deck Block
One of the most vital upgrades for FA24 engine reliability under boost is its semi-closed deck design. Older engines, like the 2.0-liter FA20DIT from the 2015 to 2021 WRX. Used an open deck where the cylinder walls had less structural support at the top of the block. The semi-closed deck on the FA24 adds cast-in metal reinforcements around the upper cylinder bores. This reinforcement prevents the cylinders from stretching or distorting when you run high boost levels. These thicker walls also reduce the risk of head gasket failures, which are issues that historically plagued boxer layouts as noted in engineering reviews from Tunxis Community College.
Advanced Induction and High Compression
The FA24DIT uses a twin-scroll turbocharger mounted low in the engine bay to minimize spool times. By separating exhaust pulses, the twin-scroll setup forces air into the cylinders much faster than a standard single-scroll unit. This turbo works alongside a direct fuel injection system to spray fuel straight into the combustion chambers at extreme pressure. This direct mist cools the intake charge, allowing Subaru to run a high 10.6:1 compression ratio on the turbocharged engine. This high compression ratio provides rapid throttle response before the turbo even builds full boost. But because the turbo model is direct-injection only, you must manage oil mist in the intake tract to keep carbon from forming on the valves.
How the FA24 Compares to Prior Boxer Engines
To understand why this block is such a massive leap forward for enthusiasts, you must compare its dimensions and architecture to the older FA20DIT and the legendary EJ257. The chart below shows how Subaru updated the core specs of its performance engines over the years.
| Engine Model | Displacement | Bore x Stroke | Compression Ratio | Deck Design | Peak Torque |
|---|---|---|---|---|---|
| FA24DIT (WRX) | 2,387 cc | 94.0 mm x 86.0 mm | 10.6:1 | Semi-Closed | 258-277 lb-ft |
| FA20DIT (WRX) | 1,998 cc | 86.0 mm x 86.0 mm | 10.6:1 | Open | 258 lb-ft |
| EJ257 (STI) | 2,457 cc | 99.5 mm x 79.0 mm | 8.2:1 | Semi-Closed | 290 lb-ft |
FA24 Engine Reliability: What Owners Should Know
The Subaru FA24 Boxer engine has built a strong name for durability since its debut in the 2019 Subaru Ascent. Owners often ask: Is the FA24 engine reliable? The short answer is yes. When you keep up with basic maintenance, this 2.4-liter platform is highly robust and has a projected lifespan of over 200,000 miles at stock power levels. But like any high-performance flat-four engine, keeping it running strong requires that you know its design strengths and its specific weak spots.
A Stronger Block Design
Subaru designed the FA24 to fix the main issues that have historically plagued some Subaru boxer engines, such as head gasket leaks and oil consumption under heavy loads. Unlike the open-deck block found in the older FA20, the FA24 uses a semi-closed deck layout. This design adds extra aluminum reinforcement around the top of the cylinder walls. This extra support keeps the cylinders from flexing under high boost pressure. The result is a much stronger engine block that holds head gaskets tight and prevents distortion during hard driving.
The RTV Sealant and Oil Starvation Threat
While the internal metal parts are very tough, the biggest threat to FA24 engine reliability comes from the oil pan assembly. Subaru uses room-temperature vulcanizing (RTV) silicone sealant instead of a solid rubber gasket to seal the oil pan. From the factory, excess RTV can squeeze out of the seams and flake off into the engine oil. These loose silicone pieces can drift into the oil pickup tube and clog the intake screen. Which can starve the engine of vital oil during high-speed cornering or track use. For drivers who push their cars hard, preventing oil starvation by cleaning out this screen is a key maintenance step.
Other Known Weak Spots
Aside from the oil pickup screen, owners should watch a few other minor areas. The plastic charge pipe on turbocharged models can crack or slip off under high boost, which causes immediate power loss. In addition, the factory positive crankcase ventilation (PCV) system can struggle to separate oil mist from engine blow-by gases. Over time, this oil mist enters the intake tract and coats the valves with carbon. Using a quality air-oil separator can solve this PCV issue and keep the valves clean, which preserves performance and long-term health.
Common FA24 Problems and Failure Points
Every engine platform has its unique quirks and vulnerabilities under stress. While overall FA24 reliability modifications help keep the boxer platform healthy, performance driving reveals specific weak spots. Enthusiasts who track their cars or increase boost levels must understand these critical areas to prevent severe engine damage.
RTV Sealant and Oil Starvation
The most discussed issue on this engine involves excess Room Temperature Vulcanizing (RTV) silicone sealant from the factory assembly line. This excess sealant can break off inside the engine and travel directly to the oil pan. Once there, it gets trapped in the screen of the oil pickup tube. Because the FA24 uses a five-sided, basket-shaped pickup screen, a partial clog still allows some oil to pass under normal driving conditions.
However, high lateral forces on a racetrack can cause the remaining oil to slosh away from the pickup tube. When combined with an RTV-clogged screen, the oil pump draws in air instead of oil. This brief drop in oil pressure leads to spun rod bearings and catastrophic block failure. Debris mitigation requires dropping the oil pan to inspect, clean, and remove any loose RTV sealant, which is a key step in preventing oil starvation on tracked vehicles.
Intake Valve Carbon Buildup
The turbocharged FA24DIT engine uses a direct-injection fuel system. Unlike the naturally aspirated FA24D found in the BRZ, which uses dual port and direct injection, the turbocharged motor sprays fuel only into the combustion chamber. This means gasoline never washes over the back of the intake valves to clean away oil mist.
Over time, oil vapors from the Positive Crankcase Ventilation (PCV) system bake onto the hot intake valves. This carbon buildup restricts airflow, causes rough idling, and degrades performance. To combat this issue, a high-quality oil separator is needed to keep oil out of the intake tract before it can coat the valves.
Factory Charge Pipe Failure
For WRX owners raising boost levels, the factory plastic charge pipe is a known weak link. Under increased pressure, the plastic pipe can flex, leak, or blow completely off its couplers. Upgrading to a sturdy aluminum pipe ensures consistent boost delivery and prevents sudden boost leaks during hard acceleration.
Summary of Common FA24 Challenges
The table below summarizes the most common issues on the FA24 engine, their direct causes, operational impact, and the recommended solutions to maintain long-term reliability.
| Problem | Cause | Impact | Fix |
|---|---|---|---|
| Pickup Screen Clog | Excess factory RTV sealant | Oil starvation on tracks | Drop pan and clean screen |
| Carbon Buildup | Direct injection design | Lost power and rough idle | Install an oil separator |
| Charge Pipe Blow-off | Weak plastic factory pipe | Sudden boost and power loss | Upgrade to aluminum pipe |
How Much Horsepower Can an FA24 Handle?
The quest for more speed is a core part of Subaru culture. When the 2022 WRX debuted, its 2.4-liter engine sparked massive interest. Understanding the limits of your powertrain is vital for maintaining long-term FA24 reliability modifications. Stock, the direct-injection FA24DIT puts out 271 horsepower at 5,600 rpm and 258 to 277 lb-ft of torque. While these numbers provide a solid baseline, the platform can do much more before you risk internal engine failure.
The Limits of Stock Internals
You can achieve substantial power gains on the stock block with basic upgrades. With common bolt-on parts like a larger downpipe, a front-mount intercooler, and a custom tune, the motor easily reaches 350 to 400 wheel horsepower (WHP). This range is highly popular because it preserves daily drivability. However, pushing past 400 WHP on stock internals is where risks rise. The factory connecting rods are the primary weak link, and they will bend under excessive cylinder pressure. Additionally, the direct-injection system faces fuel flow limits at high power levels.
Common Power Failure Points
Boosting output requires a careful look at weak factory components. The stock plastic charge pipe is notorious for blowing off or cracking under increased boost pressures. Replacing this plastic piece with a sturdier metal pipe is an essential step. It prevents sudden boost leaks that can lead to a dangerous lean run condition. Upgrading your fuel system and utilizing high-quality synthetic lubricants will also help protect your bearings under heavy loads.
Building for High Horsepower
If your goals exceed 400 WHP, upgrading to a built block is the safest path forward. Forging the pistons and rods allows the engine to withstand extreme cylinder pressures. At Crawford Performance, we have validated over 660 horsepower on built FA-series engines. A built block removes the factory mechanical weak spots, so you can tune your Subaru with confidence. Our engine builders use robust aftermarket parts to ensure your motor survives track days and street use alike.
| Power Level | WHP Range | Mods Required | Reliability Impact |
|---|---|---|---|
| Stage 1 | 280 - 310 WHP | Accessport, custom ECU tune, high-flow panel filter | Very high reliability; close to factory wear rates |
| Stage 2 | 310 - 340 WHP | Downpipe, intake, custom ECU tune | High reliability; requires shorter oil change intervals |
| Stage 2+ | 350 - 400 WHP | Downpipe, intercooler, metal charge pipe, tune | Moderate reliability; stock rods are near safe limits |
| Built Block | 400 - 600+ WHP | Forged pistons, rods, upgraded studs, Crawford block | Excellent durability for extreme power demands |
Essential FA24 Reliability Modifications
Maximizing the lifespan of your vehicle requires targeting known weak points before they lead to costly repairs. While the factory setup is solid, high-load driving and increased boost can strain key parts. By installing a few focused upgrades, you can protect your engine and enjoy consistent power. These upgrades help keep your engine healthy whether you drive on the street or the track.
Protect Your Intake Valves
Because the turbocharged 2.4-liter engine uses direct injection, fuel does not wash over the intake valves to clean them. This design can lead to carbon buildup over time, which hurts airflow and engine response. Installing a Crawford Air Oil Separator is the best way to prevent this issue. It stops oil vapors from entering the intake tract, keeping your valves clean and reducing the risk of engine knock under load.
Upgrade to a Metal Charge Pipe
The stock plastic charge pipe is prone to cracking or blowing off entirely when you increase the boost. Upgrading to a sturdy metal charge pipe is a simple way to secure your boost path and prevent sudden leaks. This modification keeps your intake system sealed under high pressure, which is critical when aiming for more horsepower. It offers peace of mind during spirited runs and sustained hard driving.
Keep Oil Temperatures Under Control
High oil temperatures can thin out your engine oil and reduce its ability to protect vital bearings. If you take your car to the track or drive under heavy loads, adding an external oil cooler is a smart safety measure. Maintaining stable oil temperatures is essential for preventing oil starvation and ensuring proper lubrication. Consistent cooling protects your rod bearings and extends overall engine life.
Improve Airflow and Response
The factory turbo inlet pipe is restrictive and can limit your turbocharger's efficiency. Replacing it with a high-flow aluminum or silicone inlet pipe improves throttle response and turbo spool. This upgrade smooths out the incoming airflow, allowing the turbo to work less to make the same amount of boost. It is an excellent supporting modification that prepares your intake system for professional tuning.
Get a Professional Tune
To pull all your upgrades together safely, you need to recalibrate the engine control unit. A professional tune optimizes your air-to-fuel ratios, boost levels, and ignition timing. This step ensures that your engine runs safely with its new modifications, which is key to long-term FA24 reliability modifications. A proper tune protects your engine from dangerous detonation while unlocking smooth, predictable power.
Recommended Upgrades Summary
To help you plan your build, here is a breakdown of these modifications, their primary reliability benefits, and their general installation difficulty:
- Air Oil Separator (AOS): Reduces carbon buildup on intake valves and lowers knock risk. Difficulty: Medium.
- Metal Charge Pipe: Prevents boost leaks and guards against pipe failure under high pressure. Difficulty: Easy.
- External Oil Cooler: Lowers engine oil temperatures during high-load track or street driving. Difficulty: Medium.
- Turbo Inlet Pipe: Restores lost airflow and improves overall turbo spool and response. Difficulty: Easy.
- Professional Tune: Optimizes air and fuel ratios to protect against dangerous engine knock. Difficulty: Hard.
When to Upgrade to a Built FA24 Block
The stock Subaru FA24 engine is a solid platform, but every factory block has its limits. If you plan to push your car past the limits of simple bolt-on upgrades, you must consider a built block. Upgrading your block before a failure occurs saves money and prevents damage to your engine accessories.
Signs You Have Reached the Stock Limits
For most drivers, the need for a built block comes down to power goals and vehicle use. While the stock block can handle daily driving with minor modifications, pushing past 400 wheel horsepower (WHP) places extreme stress on the factory rods and pistons. Frequent track use also accelerates wear, even at lower power levels. This is because long periods of high heat and high engine speeds test the limits of factory parts. If your build includes a larger turbocharger, upgrading the block is the best way to ensure FA24 engine reliability under high boost.
Short Block vs. Long Block Options
When you decide to upgrade, you have two main paths: a built short block or a full long block. A built short block includes the engine case halves, a forged crankshaft, and upgraded pistons, rods, and bearings. This path lets you reuse your factory cylinder heads, which keeps your initial costs lower. The parts inside a built block typically feature high-strength rods from Manley. They also use durable rod and main bearings from ACL or King, plus heavy-duty head studs from ARP. If you want maximum performance, a full long block adds ported cylinder heads and an upgraded valvetrain to the short block assembly. This complete setup improves high-rpm airflow and is covered in detail in our FA24 high performance upgrades manual.
Your Build Options and Warranty Support
As an authorized IAG dealer, Crawford Performance offers a complete line of built engine options to fit your goals. You can choose from pre-engineered assemblies like the IAG Stage 2, Stage 2 Plus, or Stage 3 blocks. These packages use proven forged internals to handle high boost. We also build custom in-house Crawford blocks tailored specifically to your vehicle's use case, whether you build for rally, track, or street performance. No matter which block you choose, your investment is secure. Every performance engine we build or supply is backed by a standard 12-month or 12,000-mile warranty to give you peace of mind. To find the right engine setup for your budget and power goals, check out our built FA24 long block engines guide.
Frequently Asked Questions
Is the FA24 engine reliable?
Yes, the FA24 is highly reliable under standard operating conditions. Subaru moved from an open deck design to a stronger semi-closed deck configuration for the 2.4-liter block. According to Subimods, this structural design helps the block handle combustion stress far better than older engines like the FA20. Proper routine maintenance remains critical for long-term health.
How does FA24 engine reliability compare to the older FA20?
The FA24 offers superior reliability and strength over the older FA20. It uses a larger 94 mm cylinder bore compared to the 86 mm bore of the FA20. This change increases displacement and torque without stressing internals. The newer semi-closed deck layout also handles heat and cylinder pressure much better, making it more robust for daily use.
What are the most common failure points on the FA24?
A primary concern on the FA24 is factory silicone sealant, or RTV, clogging the oil pickup screen. Excess RTV can flake off into the oil pan and restrict oil flow under high-load cornering. On turbo models, the factory plastic charge pipe is also prone to leaking boost under increased pressure. While the PCV system can allow oily vapors to enter the intake path.
Can the stock FA24 engine handle power upgrades?
Yes, the stock FA24 engine is remarkably strong compared to its predecessors. Standard internals can safely support 350 to 400 wheel horsepower with a high-quality tune and bolt-on upgrades. However, going beyond these power levels increases the risk of bending connecting rods or cracking pistons. For higher power, upgrading to a built engine is highly recommended.
What modifications help prevent FA24 engine failure?
To maximize lifespan, owners should install vital FA24 reliability modifications. A high-quality air oil separator is the single best tool to stop carbon buildup on intake valves. Adding an oil cooler helps manage lubrication temperatures under hard driving, while upgrading to a stronger metal charge pipe stops boost leaks before they cause issues.
Delaying a built block upgrade on a high-boost WRX increases your risk of sudden stock engine failure. Avoid the high costs of towing, cleanup, and unexpected downtime by choosing a proactive path. When you start your build now, you get your car back on the road faster with a secure setup ready for daily power. Whether you need a built short block with forged pistons and rods from Manley and ARP or a complete IAG Stage 3 long block. Crawford Performance has the experience to match the right engine package to your power goals. Ready to build your custom FA24 short block or long block? Call us at (717) 469-8446 or contact Crawford Performance online to discuss your build goals and get started on your order.