Subaru FA24 Specifications
| Engine Model: Subaru FA24 |
| Engine Type: 4-cycle 4-cylinder DOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 145.7 cu.in (2.38 L) |
| Rated Engine Power: 228-271 Hp (170-202 kW) at 5600 rpm |
| Fuel System Type: Direct injection or Toyota D-4S |
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The Subaru FA24 is a 2.4-liter horizontally opposed
four-cylinder engine representing the current flagship architecture of Subaru’s
FA engine family. Introduced in 2018, this powerplant succeeded the EJ series
and the smaller FA20 as the company’s primary engine for larger vehicles and
performance applications. The FA24 was engineered to deliver a balance of power,
efficiency, and durability across a diverse range of applications, from family
SUVs to the rear-wheel-drive Subaru BRZ sports coupe. The engine is offered in
two distinct configurations: the turbocharged FA24F (Direct Injection Turbo) and
the naturally aspirated FA24D (featuring Toyota’s D-4S dual injection system).
The FA24’s architecture centers on an all-aluminum cylinder block and cylinder
heads, a departure from the cast iron-lined EJ blocks that preceded it. Unlike
the open-deck design of the FA20, the FA24 employs a semi-closed deck
configuration, providing significantly increased strength for high-load
turbocharged applications. The engine retains Subaru’s signature horizontally
opposed layout, offering a low center of gravity and inherent balance. A timing
chain replaces the rubber belts of earlier EJ engines, eliminating scheduled
timing belt replacements and reducing long-term maintenance requirements.
The engine utilizes Dual Active Valve Control System (Dual AVCS), providing
continuous variable valve timing on both intake and exhaust camshafts. The FA24F
turbocharged variant employs a twin-scroll turbocharger with direct injection,
delivering a broad torque plateau from low engine speeds.
The FA24D naturally aspirated variant features a 12.5:1 compression ratio and
Toyota’s D-4S injection system, which combines port and direct injection to
optimize power output while mitigating intake valve carbon deposits. The FA24
has become Subaru’s primary powertrain across its lineup, powering the Ascent
SUV, Legacy and Outback XT models, the VB-generation WRX, and the
second-generation BRZ.
The engine operates on a four-stroke Otto cycle with either twin-scroll
turbocharged or naturally aspirated induction depending on variant. It is
configured for longitudinal, front-engine, all-wheel-drive applications in most
models, with the BRZ variant configured for longitudinal, front-engine,
rear-wheel-drive installation.
Engine Type: Horizontally opposed 4-cylinder (Boxer), water-cooled, 4-stroke.
Displacement: 2,387 cc (145.7 cu.in).
Bore x Stroke: 94.0 mm x 86.0 mm (3.70 in x 3.39 in).
Compression Ratio (FA24F Turbocharged): 10.6:1.
Compression Ratio (FA24D Naturally Aspirated): 12.5:1.
Firing Order: 1-3-2-4.
Ignition System: Electronic, direct ignition system (DIS) with coil-on-plug.
Idle Speed: 650 - 750 rpm, dependent on variant and operating conditions.
FA24F Turbocharged
Maximum Power: 194-202 kW (260-271 hp) @ 5,600 rpm.
Maximum Torque: 350-376 Nm (258-277 lb-ft) @ 2,000 - 4,800 rpm.
Turbocharger: Twin-scroll turbocharger with integrated wastegate.
Maximum Boost Pressure: 1.0 - 1.2 bar (14.5 - 17.4 psi) relative pressure.
Redline: 6,800 rpm.
FA24D Naturally Aspirated
Maximum Power: 170-172 kW (228-231 hp) @ 7,000 rpm.
Maximum Torque: 250 Nm (184 lb-ft) @ 3,700 rpm.
Redline: 7,500 rpm.
The cylinder block is constructed from cast aluminum
with a semi-closed deck design, providing enhanced rigidity compared to the
open-deck FA20. The semi-closed configuration features reinforced bridges
between the cylinder bores and the outer block wall, increasing strength for
high-load turbocharged operation. The block incorporates five main bearings
supporting the crankshaft and utilizes cast-in-place iron cylinder liners.
Cylinder Bore Diameter: 94.0 mm (3.70 in)
Main Bearing Journal Diameter: 60.0 mm (2.36 in)
Piston Material: High-temperature aluminum alloy with cooling gallery in
turbocharged variants. Piston Cooling: Oil jets are mounted in the cylinder
block to direct a continuous spray of engine oil to the underside of each piston
crown. Crankshaft: Forged steel, fully counter-weighted.
Connecting Rods: Asymmetrically designed forged steel, fracture-split
construction. The offset rod design allows for the larger bore and stroke
dimensions within a compact crankcase envelope. Cylinder Block Construction:
Die-cast aluminum with semi-closed deck and cast-in iron liners.
The cylinder heads are manufactured from aluminum
alloy, with separate castings for each cylinder bank. Each head houses a DOHC
valvetrain with four valves per cylinder for a total of 16 valves. Dual AVCS
(Active Valve Control System) provides continuous variable valve timing on both
intake and exhaust camshafts, with a range of up to 50 degrees of crankshaft
rotation on the intake side and 45 degrees on the exhaust side.
Valvetrain: DOHC, chain-driven, with 16 valves total. Dual AVCS provides
independent variable valve timing on intake and exhaust camshafts. Bucket-type
mechanical tappets are used, requiring periodic valve clearance adjustment.
Intake Valve Diameter: 36.0 mm (1.42 in)
Exhaust Valve Diameter: 30.0 mm (1.18 in)
Valve Lift (Intake): 10.0 mm (0.394 in)
Valve Lift (Exhaust): 9.5 mm (0.374 in)
Valve Seat Material: High-strength sintered alloy
Valve Spring Material: High-tensile steel with beehive design
Intake Valve Clearance: 0.20 - 0.25 mm (0.008 - 0.010 in)
Exhaust Valve Clearance: 0.25 - 0.30 mm (0.010 - 0.012 in)
Camshaft Drive: Silent-type Morse chain with automatic hydraulic tensioner
The fuel system configuration varies between the FA24F
and FA24D variants.
FA24F Turbocharged
The FA24F utilizes a direct injection (DI) system with fuel delivered directly
into the combustion chamber. A high-pressure pump supplies fuel to the common
rail, with injection pressures up to 25 MPa (3,625 psi). This configuration
enables precise fuel metering and charge cooling but lacks port injectors,
making intake valve carbon accumulation a potential maintenance consideration.
Fuel Injectors: High-pressure solenoid or piezoelectric injectors with
multi-hole nozzles.
High-Pressure Fuel Pump: Single-piston plunger pump driven by the camshaft.
Common Rail Pressure: 20 - 25 MPa (2,900 - 3,625 psi).
FA24D Naturally Aspirated
The FA24D utilizes Toyota’s D-4S dual injection system, combining direct
injection with port fuel injection. Each cylinder is served by one direct
injector mounted in the cylinder head and one port injector mounted in the
intake manifold. The system switches between injection modes based on engine
load and speed, optimizing power, efficiency, and intake valve cleanliness.
Direct Injectors: High-pressure injectors operating at up to 20 MPa (2,900 psi).
Port Injectors: Low-pressure injectors operating at 400 - 500 kPa (58 - 73 psi).
High-Pressure Fuel Pump: Single-piston plunger pump driven by the camshaft.
Intake Manifold: Composite resin (plastic) construction with integrated tumble
control valves.
Throttle Body: Electronically controlled drive-by-wire (DBW) system with a bore
diameter of 70 mm (2.76 in).
Fuel Requirement: Minimum octane rating of 95 RON (Research Octane Number) / 91
AKI (Anti-Knock Index) for both variants; premium fuel recommended for maximum
performance.
The lubrication system is a fully pressurized wet-sump
design incorporating a variable-displacement oil pump. The pump adjusts its
output based on engine speed and load, reducing parasitic losses. The system
includes a full-flow oil filter with an integral bypass valve and a plate-type
oil cooler for temperature regulation.
Oil Pump Type: Variable-displacement vane-type pump
Recommended Oil Viscosity (FA24F): 0W-20 or 5W-30, fully synthetic
Recommended Oil Viscosity (FA24D): 0W-20, fully synthetic
Oil Capacity (with filter change): 5.0 - 5.5 liters (5.3 - 5.8 qt)
Oil Pressure (at 3,000 rpm, warm): 300 - 400 kPa (43.5 - 58.0 psi)
Oil Pan Material: Stamped steel or cast aluminum with integrated baffling and
windage tray
Oil Cooler: Plate-type oil-to-water heat exchanger mounted to the cylinder block
The cooling system is a pressurized design utilizing a
high-flow centrifugal water pump driven by the engine’s accessory drive belt. A
wax-type thermostat regulates coolant flow. The turbocharged FA24F incorporates
additional cooling capacity, including a dedicated circuit for the turbocharger
bearing housing.
Coolant Type: Ethylene-glycol based antifreeze
Coolant Capacity (engine and radiator): 7.0 - 8.0 liters (7.4 - 8.5 qt)
Thermostat Opening Temperature: 82 - 88 °C (180 - 190 °F)
Radiator Cap Pressure: 90 - 110 kPa (13.1 - 16.0 psi)
Water Pump Type: Centrifugal with a mechanical seal
Timing Drive: Silent-type Morse chain with an automatic
hydraulic tensioner utilizing engine oil pressure. The tensioner incorporates a
ratchet mechanism to maintain tension during engine start-up. The system is
designed for the operational life of the engine under proper maintenance
conditions.
Accessory Drive: Single serpentine belt driving the alternator, water pump, and
air conditioning compressor. An automatic spring-loaded tensioner maintains
consistent belt tension.
Emission Control System: Includes close-coupled three-way catalytic converters,
upstream and downstream heated oxygen sensors, a Positive Crankcase Ventilation
(PCV) system, and an evaporative emissions control system. The engine complies
with Euro 6d, LEV3-ULEV70, and EPA Tier 3 emission standards.
Engine Management System: Subaru-sourced ECU with integrated boost pressure
control (FA24F), dual injection mode switching (FA24D), Dual AVCS actuation, and
idle speed control. The ECU utilizes MAP (Manifold Absolute Pressure), MAF (Mass
Air Flow), and intake air temperature sensors for load detection.
Overall Length: 660 mm (26.0 in)
Overall Width: 640 mm (25.2 in)
Overall Height: 540 mm (21.3 in)
Dry Weight (complete engine): 135 kg (298 lb) for naturally aspirated variant
Dry Weight (complete engine): 145 kg (320 lb) for turbocharged variant
Valve Clearance: Mechanical bucket-type tappets require
manual adjustment. Inspection interval is 96,000 km (60,000 miles). Timing
Chain: Chain and tensioner condition should be assessed if abnormal noise or
timing correlation diagnostic trouble codes are present. Spark Plug Type: NGK
ILKAR7H11 or equivalent iridium. Spark Plug Gap: 1.0 - 1.1 mm (0.039 - 0.043
in). Spark Plug Replacement Interval: 96,000 km (60,000 miles).
Engine Oil Change Interval: 10,000 km (6,000 miles) or 12 months under normal
operating conditions. Engine Oil Filter Change Interval: With every oil change.
Coolant Replacement Interval: 120,000 km (75,000 miles) or 5 years. Air Filter
Element: Replace every 40,000 km (25,000 miles); more frequent replacement is
required in dusty environments. Drive Belt Inspection: Every 10,000 km (6,000
miles) for cracks, fraying, glazing, and proper tension.
Direct Injection Maintenance (FA24F): Intake valve carbon cleaning is not a
scheduled maintenance item but may be required at extended intervals depending
on fuel quality and operating conditions. Walnut blasting is the recommended
cleaning method. RTV Sealant (Early Production): Early FA24D production units
(2022 BRZ/GR86) required inspection for excess RTV sealant from the oil pan
assembly that could obstruct the oil pickup tube.
Cylinder Head Bolts: 40 Nm (30 lb-ft)
Main Bearing Cap Bolts: 30 Nm (22 lb-ft)
Connecting Rod Cap Bolts: 20 Nm (15 lb-ft)
Camshaft Bearing Cap Bolts: 12 Nm (9 lb-ft)
Intake Manifold Bolts: 20 Nm (15 lb-ft)
Exhaust Manifold Nuts: 25 Nm (18 lb-ft)
Turbocharger Mounting Nuts (FA24F): 30 Nm (22 lb-ft)
High-Pressure Fuel Pump Mounting Bolts: 20 Nm (15 lb-ft)
Oil Pan Bolts: 12 Nm (9 lb-ft)
Valve Cover Bolts: 10 Nm (7 lb-ft)
Spark Plugs: 20 Nm (15 lb-ft)
Crankshaft Pulley Bolt: 200 Nm (148 lb-ft)
Flex Plate / Drive Plate Bolts: 80 Nm (59 lb-ft)
The Subaru FA24 engine is utilized across Subaru’s
current-generation lineup, serving as the primary powertrain for larger SUVs,
performance sedans, and the rear-wheel-drive sports coupe developed with Toyota.
FA24F Turbocharged Applications
2019 - Present Subaru Ascent: The debut application for the FA24F, serving as
the sole engine option for Subaru’s three-row mid-size SUV.
2020 - Present Subaru Legacy XT / Outback XT: Installed as the high-performance
engine option for the Legacy sedan and Outback crossover, reviving the XT
designation.
2022 - Present Subaru WRX (VB Generation): The standard engine for the
fifth-generation WRX, replacing the previous EJ25 and FA20F engines. The FA24F
in this application delivers 202 kW (271 hp) and 350 Nm (258 lb-ft).
2023 - Present Subaru Crosstrek Wilderness: Applied in the off-road-oriented
Crosstrek Wilderness variant, offering increased torque for trail capability.
FA24D Naturally Aspirated Applications
2022 - Present Subaru BRZ (ZD Generation): The second-generation Subaru BRZ
utilizes the FA24D with D-4S dual injection, delivering 170 kW (228 hp) and 250
Nm (184 lb-ft). The engine is configured for longitudinal, front-engine,
rear-wheel-drive installation.
2022 - Present Toyota GR86 (ZN Generation): The Toyota GR86, developed jointly
with Subaru, utilizes the same FA24D engine with calibration differences. The
engine is assembled by Subaru and supplied to Toyota under the technical
partnership.
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