The Subaru FA20F motor is a direct-injected turbo engine found in the 2015+ WRX. It features a four-cylinder horizontally-opposed "Boxer" layout with a twin-scroll turbocharger. The 2014+ Forester XT uses essentially the same engine, but with small changes and a different designation (FA20E).
| Specification | Standard | Metric |
|---|---|---|
| Engine Code | FA20F | FA20F |
| Displacement | 122ci | 1998cc (2.0L) |
| Layout | H4 BOXER | H4 BOXER |
| Power | 268 BHP @ 5600 RPM (WRX) 250 BHP @ 5600 RPM (XT) |
197 kW @ 5600 RPM (WRX) 184 kW @ 5600 RPM (XT) |
| Torque | 258 Lb-Ft @ 2000 RPM (WRX / XT) | 350 Nm @ 2000 RPM (WRX / XT) |
| Rev Limit | 6700 RPM | 6700 RPM |
| Assembly | Oizumi, Japan | Oizumi, Japan |
| Firing Order | 1-3-2-4 | 1-3-2-4 |
| Spark Plug | NGK ILKAR8H6 | NGK ILKAR8H6 |
| Fuel Pump Flow | 40.4 Gallons (US)/Hr | 153 L/Hr |
| Specification | Standard | Metric |
|---|---|---|
| Block Material | Cast Aluminum | Cast Aluminum |
| Block Design | Open Deck | Open Deck |
| # of Cylinders | 4 | 4 |
| Bore Diameter | 3.386" | 86mm |
| Bore Spacing | 4.449" | 113mm |
| Cylinder Liners | Cast-In Iron | Cast-In Iron |
| # of Main Bearings | 5 | 5 |
| Cylinder Block Height * | 8.071" (R) 8.073" (L) |
205.0mm (R) 205.05mm (L) |
| Min. Cyl. Block Height | 8.067" | 204.9mm |
| Cyl. Block Warpage Limit | 0.00098" | 0.025mm |
| Cyl. Liner ID | 3.3860 - 3.3864" (A) 3.3856 - 3.3860" (B) |
86.005 - 86.015mm (A) 85.995 - 86.005mm (B) |
| Cyl. Liner Cylindricality Limit | 0.0012" | 0.030mm |
| Cyl. Liner Out-of-Roundness Limit | 0.0012" | 0.030mm |
| Bore ID Limit | 3.4057" | 86.505mm |
* - Difference in Cylinder Block Height is due to the water pump being placed on one side of the block and the resulting thermal expansion difference
Take measurements in the thrust and pin directions (A + B) at the specified heights. Verify that the block is at 68°F (20°C) for all measurements.
$$Cylindricatlity =\dfrac {x_{\max }-x_{\min }}{2}$$
$$x_{\max } = \textrm{largest value of all the cylinder liner ID measurements}$$
$$x_{\min } = \textrm{smallest value of all the cylinder liner ID measurements}$$
Calculate the Out-Of-Roundness at each height measurement (H1 - H4).
$$OOR =\dfrac {x_{\max }-x_{\min }}{2}$$
$$x_{\max } = \textrm{larger measurement value at H1}$$
$$x_{\min } = \textrm{smaller measurement value at H1}$$
The figures below are the OEM Subaru specifications for the stock OEM Subaru pistons. If you are rebuilding the engine using an aftermarket forged piston you will need to run considerably higher tolerances to accommodate the greater thermal expansion. Please consult your piston supplier for appropriate clearances.
| Specification | Standard | Metric |
|---|---|---|
| Piston Material | Hypereutectic Cast Aluminum with Anti-Friction Skirt Coating |
Hypereutectic Cast Aluminum with Anti-Friction Skirt Coating |
| Static Compression Ratio | 10.6:1 | 10.6:1 |
| Piston Weight | 360g | 360g |
| Piston Wrist Pin Diameter (Gudgeon Pin) |
0.866" | 22mm |
| Piston Wrist Pin Offset | 0.039" | 1mm |
| Piston Wrist Pin Weight | 136g | 136g |
| Piston Crown Volume | 0.8cc | 0.8cc |
| Compression Height | 1.291" | 32.8mm |
| Piston Outer Diameter | 3.3852 - 3.3856" (A) 3.3856 - 3.3860" (B) 3.3947 - 3.3955" (0.25mm OS) 3.4045 - 3.4053" (0.50mm OS) |
85.985 - 85.995mm (A) 85.975 - 87.985mm (B) 86.225 - 86.245mm (0.25mm OS) 86.475 - 86.495mm (0.50mm OS) |
| Piston to Wall Clearance | 0.00039” - 0.00118” | 0.01mm – 0.03mm |
| Piston Gauge Height | 1.57" | 40mm |
| Piston Pin Clearance | 0.0002 - 0.0003" | 0.004 - 0.008mm |
| Top Comp. Ring Axial Height | 0.0394" | 1.0mm |
| Top Compression Ring Gap | 0.0079 - 0.0098" | 0.20 - 0.25mm |
| Second Comp. Ring Axial Height | 0.0472" | 1.2mm |
| Second Compression Ring Gap | 0.0157 - 0.0197" | 0.40 - 0.50mm |
| Oil Control Ring Gap | 0.0039 - 0.0138" | 0.10 - 0.35mm |
| Top Compression Ring Clearance | 0.0016 - 0.0031" | 0.040 - 0.080mm |
| Second Compression Ring Clearance | 0.0018 - 0.0033" | 0.045 - 0.085mm |
| Piston to Pin Clearance | 0.0002 - 0.0003" | 0.004 - 0.008mm |
| Pin to Rod Bushing Clearance | 0.0002 - 0.0010" | 0.004 - 0.026mm |
The figures below are the OEM Subaru specifications for the stock OEM Subaru rods. If you are rebuilding the engine using an aftermarket forged rod you may need to run greater clearances for the power level.
| Specification | Standard | Metric |
|---|---|---|
| Con Rod Material | Forged Steel | Forged Steel |
| Con Rod Design | Asymmetrical I-Beam with Cracked Caps and Rod Bolts |
Asymmetrical I-Beam with Cracked Caps and Rod Bolts |
| Con Rod Weight | 492g | 492g |
| Con Rod Length | 5.090" | 129.29mm |
| Big End Bore | 2.087" | 53.01mm |
| Big End Width | 0.843" | 21.41mm |
| Pin Bore | 0.8671" | 22.02mm |
| Rod Bolt Torque | 18.44 ft-lbs | 25Nm |
The figures below are the OEM Subaru specifications for the stock OEM Subaru crankshaft. If you are rebuilding the engine using an aftermarket crankshaft you may need to run different clearances.
| Specification | Standard | Metric |
|---|---|---|
| Design / Material | 8CW Flat-Plane Nitrided Forged Steel | 8CW Flat-Plane Nitrided Forged Steel |
| Stroke | 3.386" | 86mm |
| Rod Bearing Thickness (Center) |
0.0587 - 0.0594" (Std) 0.0595 - 0.0596" (0.0012" US) 0.0599 - 0.0600" (0.0020" US) 0.0638 - 0.0640" (0.0098" US) |
1.492 - 1.508mm (Std) 1.511 - 1.515mm (0.03mm US) 1.521 - 1.525mm (0.05mm US) 1.621 - 1.625mm (0.25mm US) |
| Crankshaft Pin OD (Rod Bearing Journal) |
1.9676 - 1.9685" (Std) 1.9664 - 1.9673" (0.0012" US) 1.9656 - 1.9665" (0.0020" US) 1.9577 - 1.9587" (0.0098" US) |
49.976 - 50.000mm (Std) 49.946 - 49.970mm (0.03mm US) 49.926 - 49.950mm (0.05mm US) 49.726 - 49.750mm (0.25mm US) |
| Crankshaft Pin Cylindricality |
0.0002" | 0.006mm |
| Crankshaft Pin Out-of-Roundness |
0.0002" | 0.005mm |
| Crankshaft Pin Grinding Limit (dia.) |
1.9577" | 49.726mm |
| Rod Bearing Oil Clearance | 0.0010 - 0.0022" | 0.025 - 0.055mm |
| Main Bearing Thickness Position #1 - 4 (Center) |
0.0982 - 0.0989" (Std) 0.0992 - 0.0993" (0.0012" US) 0.0996 - 0.0997" (0.0020" US) 0.1035 - 0.1036" (0.0098" US) |
2.495 - 2.513mm (Std) 2.519 - 2.522mm (0.03mm US) 2.529 - 2.532mm (0.05mm US) 2.629 - 2.632mm (0.25mm US) |
| Main Bearing Thickness Position #5 Only (Center) |
0.0981 - 0.0989" (Std) 0.0991 - 0.0992" (0.0012" US) 0.0995 - 0.0996" (0.0020" US) 0.1034 - 0.1035" (0.0098" US) |
2.493 - 2.511mm (Std) 2.517 - 2.520mm (0.03mm US) 2.527 - 2.530mm (0.05mm US) 2.627 - 2.630mm (0.25mm US) |
| Main Journal OD | 2.6766 - 2.6775" (Std) 2.6754 - 2.6763" (0.0012" US) 2.6746 - 2.6755" (0.0020" US) 2.6667 - 2.6677" (0.0098" US) |
67.985 - 68.009mm (Std) 67.955 - 67.979mm (0.03mm US) 67.935 - 67.959mm (0.05mm US) 67.735 - 67.759mm (0.25mm US) |
| Crankshaft Bending Limit | 0.0014" | 0.035mm |
| Crankshaft Main Journal Cylindricality |
0.0002" | 0.006mm |
| Crankshaft Main Journal Out-of-Roundness |
0.0002" | 0.005mm |
| Crankshaft Main Journal Grinding Limit (dia.) |
2.6667" | 67.735mm |
| Thrust Clearance | 0.00512 - 0.01213" | 0.130 - 0.308mm |
| Main Oil Clearance | 0.00051 - 0.00122" | 0.013 - 0.031mm |
| Specification | Standard | Metric |
|---|---|---|
| Head Design | DOHC 16-Valve with Dual AVCS |
DOHC 16-Valve with Dual AVCS |
| Combustion Chamber Volume | 40.3cc | 40.3cc |
| Rocker Type | Roller Rocker (INT/EXH) | Roller Rocker (INT/EXH) |
| Rocker Ratio | 1.59:1 (INT/EXH) | 1.59:1 (INT/EXH) |
| Spring Retainer Material | Hi-Strength Steel | Hi-Strength Steel |
| Spring Retainer Weight | 11.38g | 11.38g |
| Intake Camshaft Clearance (Note: Measure at 68° F / 20° C) |
0.0051" (Std) 0.0039" (Min) - 0.0059" (Max) |
0.13mm (Std) 0.10mm (Min) - 0.15mm (Max) |
| Exhaust Camshaft Clearance (Note: Measure at 68° F / 20° C) |
0.0087" (Std) 0.0079" (Min) - 0.0095" (Max) |
0.22mm (Std) 0.20mm (Min) - 0.24mm (Max) |
| Cylinder Head Warp Limit | 0.00079" | 0.020mm |
| Grinding / Surfacing Limit | 3.874" Height 0.004" Removed |
98.4mm Height 0.1mm Removed |
| Cylinder Head Height | 3.878" | 98.5mm |
| Valve Length | 4.132" (INT) 3.854" (EXH) |
104.95mm (INT) 97.9mm (EXH) |
| Valve Angle | 14° (INT/EXH) 28° Included |
14° (INT/EXH) 28° Included |
| Intake Valve Specs | 1.38" (Face Diameter) 0.217" (Stem Diameter) 45.5g (Weight) |
35mm (Face Diameter) 5.5mm (Stem Diameter) 45.5g (Weight) |
| Exhaust Valve Specs | 1.14" (Face Diameter) 0.217" (Stem Diameter) 37.0g (Weight) |
29mm (Face Diameter) 5.5mm (Stem Diameter) 37.0g (Weight) |
| Valve Head Edge / Margin Thickness | 0.031 - 0.047" (INT) 0.039 - 0.055" (EXH) |
0.8 - 1.2mm (INT) 1.0 - 1.4mm (EXH) |
| Valve Stem Diameter | 0.2148 - 0.2154" (INT) 0.2144 - 0.2150" (EXH) |
5.455 - 5.470 (INT) 5.445 - 5.460mm (EXH) |
| Valve Guide ID | 0.2165 - 0.2170" (INT/EXH) | 5.500 - 5.512mm (INT/EXH) |
| Valve Stem to Guide Clearance | 0.0012 - 0.0022" (INT) 0.0016 - 0.0026" (EXH) |
0.030 - 0.057mm (INT) 0.040 - 0.067mm (EXH) |
| Valve Guide Protrusion Limit | 0.449 - 0.465" | 11.4 - 11.8mm |
| Valve Shim ID | 0.2165 - 0.2189" | 5.500 - 5.560mm |
| Valve Spring Type | Single-Coil Steel | Single-Coil Steel |
| Valve Spring Dims 6-Speed Trans |
1.617" (Free Length) 1.299" (Set Length) 0.866" (Comp. Height) |
41.06mm (Free Length) 33.0mm (Set Length) 22.0mm (Comp. Height) |
| Valve Spring Dims CVT Trans |
1.641" (Free Length) 1.299" (Set Length) 0.866" (Comp. Height) |
41.68mm (Free Length) 33.0mm (Set Length) 22.0mm (Comp. Height) |
| Valve Spring Tension 6-Speed Trans |
40.92 - 47.22 Lbs (Set) 124.11 - 137.15 Lbs (Comp) |
18.56 - 21.41 kgf (Set) 56.29 - 62.20 kgf (Comp) 182 - 210 N (Set) 552 - 610 N (Comp) |
| Valve Spring Tension CVT Trans |
40.92 - 47.22 Lbs (Set) 112.87 - 124.56 Lbs (Comp) |
18.56 - 21.41 kgf (Set) 51.19 - 56.49 kgf (Comp) 182 - 210 N (Set) 502 - 554 N (Comp) |
| Valve Seating Width | 0.031 - 0.063" (INT) 0.043" - 0.067" (EXH) |
0.8 - 1.6mm (INT) 1.1 - 1.7mm (EXH) |
| Valve Seating Angle | 45° | 45° |
$$R = A + 1.69 × (B – 0.13mm (0.0051"))$$
A = Current Valve Shim Thickness
B = Measured Cam Clearance
R = Required Valve Shim Thickness
$$R = A + 1.87 × (B – 0.22mm (0.0087"))$$
A = Current Valve Shim Thickness
B = Measured Cam Clearance
R = Required Valve Shim Thickness
| Specification | Standard | Metric |
|---|---|---|
| Camshaft Duration Seat-to-Seat |
236° (INT) 246° (EXH) |
236° (INT) 246° (EXH) |
| Camshaft Lift | 0.403" (INT) 0.399" (EXH) |
10.24mm (INT) 10.14mm (EXH) |
| AVCS Cam Phasing Range | 68° (INT) 54° (EXH) |
68° (INT) 54° (EXH) |
| Intake Valve Timing (Open) |
42° BTDC - 26° ATDC | 42° BTDC - 26° ATDC |
| Intake Valve Timing (Close) |
14° ABDC - 82° ABDC | 14° ABDC - 82° ABDC |
| Exhaust Valve Timing (Open) |
66° BBDC - 11° BBDC | 66° BBDC - 11° BBDC |
| Exhaust Valve Timing (Close) |
0° ATDC - 55° ATDC | 0° ATDC - 55° ATDC |
| Base Circle Diameter | 1.339" | 34mm |
| Camshaft Journal OD | 1.0215 - 1.0222" | 25.946 - 25.963mm |
| Thrust Clearance | 0.0027 - 0.0047" | 0.068 - 0.116mm |
| Oil Clearance | 0.0015 - 0.0028" | 0.037 - 0.072mm |
| Lobe Height | 1.588 - 1.592" (Std. INT) 1.652 - 1.656" (Fuel Pump Drive INT) 1.583 - 1.587" (EXH) |
40.34 - 40.44mm (Std. INT) 41.95 - 42.05mm (Fuel Pump Drive INT) 40.20 - 40.30mm (EXH) |
| Specification | Standard | Metric |
|---|---|---|
| Water Pump Flow Rate | 65.5 Gal(US)/min | 248 L/min |
| Thermostat Open Temp | 187 - 194 °F | 86 - 90 °C |
| Radiator Cap Pressure | 14 - 18 PSI | 93 - 123 kPa 0.95 - 1.25 kg/cm² |
| Specification | Standard | Metric |
|---|---|---|
| Oil Pump Dimensions Diameter x Thickness |
3.03" x 0.55" | 77mm x 14mm |
| Oil Pressure at 248 °F / 120°C |
5.1 PSI (600 RPM) 46.6 PSI (6700 RPM) |
35 kPa / 0.4 kg/cm² (600 RPM) 321 kPa / 3.3 kg/cm² (6700 RPM) |
| Oil Flow Volume at 248 °F / 120°C |
7.8 Qt/min (US) (600 RPM) 63.6 Qt/min (US) (6700 RPM) |
7.4 L/min (600 RPM) 60.2 L/min (6700 RPM) |
| Relief Valve Pressure | 102 PSI | 700 kPa 7.1 kg/cm² |
| Oil Viscosity | 5W30 Synthetic | 5W30 Synthetic |
| Specification | Standard | Metric |
|---|---|---|
| Base Ignition Timing | 10°±10° at 700 RPM | 10°±10° at 700 RPM |
| Idle Speed | 700±100 RPM (A/C OFF) 700 - 865±50 RPM (A/C ON) |
700±100 RPM (A/C OFF) 700 - 865±50 RPM (A/C ON) |
| Compression Pressure 200 - 300 RPM (Cranking) |
196 - 254 PSI | 1350 - 1750 kPa 14 - 18 kg/cm² |
| Intake Manifold Vacuum at Idle | -17.72 inHg (A/C OFF) | -60.0 kPa (A/C OFF) -450 mmHg (A/C OFF) |
Preventing Subaru Ringland Failure in the WRX, STI, etc.
Subaru Equal vs. Unequal Length Headers
Car Overheating? Learn to Diagnose, Fix, and Prevent It
Join our email list to be notified when we release new content.
We respect your inbox and send only 1 - 4 emails per month.
We will never spam, sell, or do annoying things with it ... ever.
For just one share a month, you too can save a car-tard from themselves.
