LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Subaru >> 2021 >> WRX Base >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 8 (Engine Mechanical System (2.5L)) >> General Description >> Specification
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Section 8 (Engine Mechanical System (2.5L)): General Description: Specification

WARNING: This page is about a different variant/trim than selected.
Engine Model 2.5 L
Cylinder arrangement Horizontally opposed, liquid cooled, 4-cylinder, 4-stroke gasoline engine
Valve system mechanism Belt driven, double overhead camshaft, 4-valve/cylinder
Bore x Stroke mm (in) 99.5 x 79.0 (3.92 x 3.11)
Displacement cm3 (cu in) 2, 457 (150)
Compression ratio 8.2
Compression pressure (at 200 - 300 r/min) kPa (kg/cm2 , psi) Standard 981 - 1, 177 (10 - 12, 142 - 171)
Number of piston rings Compression ring: 2 Oil ring: 1
Intake valve timing Open Max. retard ATDC 5°
Min. advance BTDC 47°
Close Max. retard ABDC 65°
Min. advance ABDC 13°
Exhaust valve timing Open Max. retard BBDC 28°
Min. advance BBDC 72°
Close Max. retard ATDC 32°
Min. advance BTDC 12°
Valve clearance mm (in) Inspection value Intake 0.20+0.04-0.06 (0.0079+0.0016-0.0024 )
Exhaust 0.35±0.05 (0.0138±0.0020)
Adjustment value Intake 0.20+0.01-0.03 (0.0079+0.0004-0.0012 )
Exhaust 0.35±0.02 (0.0138±0.0008)
Idle speed (Gear shift lever is in neutral) r/min No load Standard 700±100
A/C ON Standard 750±100
Ignition order 1 → 3 → 2 → 4
Ignition timing BTDC/{r/min} Standard 15°±10°/700
NOTE: OS: Oversize US: Undersize
Belt tension adjuster Adjuster rod protrusion amount mm (in) 5.2 - 6.2 (0.2047 - 0.2441)
Camshaft Bending limit mm (in) 0.020 (0.0008)
Cam lobe height mm (in) Intake Standard 46.55 - 46.65 (1.8327 - 1.8366)
Exhaust Standard 46.75 - 46.85 (1.8405 - 1.8445)
Cam base circle diameter mm (in) Standard 37.0 (1.4567)
Journal O.D. mm (in) Front Standard 37.946 - 37.963 (1.4939 - 1.4946)
Center, rear Standard 29.946 - 29.963 (1.1790 - 1.1796)
Oil clearance mm (in) Standard 0.037 - 0.072 (0.0015 - 0.0028)
Thrust clearance mm (in) Standard 0.068 - 0.116 (0.0027 - 0.0047)
Cylinder head Warping limit (Mating surface with cylinder block) mm (in) 0.035 (0.0014)
Grinding limit mm (in) 0.3 (0.0118)
Standard height mm (in) 127.5 (5.0197)
Valve seat Seating angle between valve and valve seat 90°
Contacting width between valve and valve seat mm (in) Intake Standard 0.6 - 1.4 (0.0236 - 0.0551)
Exhaust Standard 1.2 - 1.8 (0.0472 - 0.0709)
Valve guide Clearance between the valve guide and valve stem mm (in) Intake Standard 0.030 - 0.057 (0.0012 - 0.0022)
Exhaust Standard 0.040 - 0.067 (0.0016 - 0.0026)
Inside diameter mm (in) 6.000 - 6.012 (0.2362 - 0.2367)
Valve stem outer diameters mm (in) Intake 5.955 - 5.970 (0.2344 - 0.2350)
Exhaust 5.945 - 5.960 (0.2341 - 0.2346)
Valve guide protrusion amount mm (in) 15.8 - 16.2 (0.6220 - 0.6378)
Valve Head edge thickness mm (in) Intake Standard 1.0 - 1.4 (0.0394 - 0.0551)
Exhaust Standard 1.3 - 1.7 (0.0512 - 0.0669)
Overall length mm (in) Intake 104.4 (4.1102)
Exhaust 104.65 (4.1201)
Valve spring Free length (reference) mm (in) 53.48 (2.1055)
Tension/spring height N (kgf, lb)/mm (in) Set 204.6 - 235.4 (20.86 - 24.00, 46.00 - 52.93)/36.0 (1.4173)
Lift 363.5 - 401.7 (37.07 - 40.96, 81.73 - 90.32)/26.7 (1.0512)
Squareness 2.5°, 2.3 mm (0.0906 in) or less
Valve lifter Outer diameter mm (in) Standard 34.959 - 34.975 (1.3763 - 1.3770)
Valve lifter mating surface inner diameter mm (in) Standard 34.994 - 35.016 (1.3777 - 1.3786)
Valve lifter and valve lifter mating surface clearance mm (in) Standard 0.019 - 0.057 (0.0007 - 0.0022)
Cylinder block Warping limit (Mating surface with cylinder head) mm (in) 0.025 (0.0010)
Grinding limit mm (in) 0.1 (0.0039)
Standard height mm (in) 201.0 (7.9134)
Cylindricality mm (in) Limit 0.015 (0.0006)
Out-of-roundness mm (in) Limit 0.010 (0.0004)
Clearance between cylinder and piston at 20°C (68°F) mm (in) Standard -0.010 - 0.010 (-0.0004 - 0.0004)
Cylinder inner diameter boring limit (diameter) mm (in) To 100.005 (3.9372)
Piston Piston grade point mm (in) 38.2 (1.5039)
Outer diameter mm (in) Standard A 99.505 - 99.515 (3.9175 - 3.9179)
B 99.495 - 99.505 (3.9171 - 3.9175)
0.25 (0.0098) OS 99.745 - 99.765 (3.9270 - 3.9278)
0.50 (0.0197) OS 99.995 - 100.015 (3.9368 - 3.9376)
Piston pin Degree of fit Piston pin must be fitted into position with thumb at 20°C (68°F).
Clearance between piston pin hole and piston pin mm (in) Standard 0.004 - 0.008 (0.0002 - 0.0003)
Piston ring Piston ring gap mm (in) Top ring Standard 0.23 - 0.28 (0.0091 - 0.0110)
Second ring Standard 0.37 - 0.52 (0.015 - 0.0205)
Oil ring Standard 0.20 - 0.50 (0.0079 - 0.0197)
Clearance between piston ring and piston ring groove mm (in) Top ring Standard 0.040 - 0.080 (0.0016 - 0.0031)
Second ring Standard 0.030 - 0.070 (0.0012 - 0.0028)
Connecting rod and connecting rod bearing Bend or twist per 100 mm (3.9370 in) in length mm (in) Limit 0.10 (0.0039)
Thrust clearance mm (in) Standard 0.070 - 0.330 (0.0028 - 0.0130)
Oil clearance mm (in) Standard 0.017 - 0.045 (0.0007 - 0.0018)
Bearing size
(Thickness at center) mm (in)
Standard 1.490 - 1.506 (0.0587 - 0.0593)
0.03 (0.0012) US 1.504 - 1.512 (0.0592 - 0.0595)
0.05 (0.0020) US 1.514 - 1.522 (0.0596 - 0.0599)
0.25 (0.0098) US 1.614 - 1.622 (0.0635 - 0.0639)
Bushing of small end Clearance between piston pin and bushing mm (in) Standard 0 - 0.022 (0 - 0.0009)
Crankshaft and crankshaft bearing Bending limit mm (in) 0.035 (0.0014)
Crank pin Cylindricality mm (in) Limit 0.004 (0.0002)
Out-of-roundness mm (in) Limit 0.003 (0.0001)
Grinding limit (dia.) mm (in) To 51.734 (2.0368)
Crank journal Cylindricality mm (in) Limit 0.006 (0.0002)
Out-of-roundness mm (in) Limit 0.005 (0.0002)
Grinding limit (dia.) mm (in) To 59.742 (2.3520)
Crank pin outer diameter mm (in) Standard 51.976 - 52.000 (2.0463 - 2.0472)
0.03 (0.0012) US 51.954 - 51.970 (2.0454 - 2.0461)
0.05 (0.0020) US 51.934 - 51.950 (2.0447 - 2.0453)
0.25 (0.0098) US 51.734 - 51.750 (2.0368 - 2.0374)
Crank journal outer diameter mm (in) Standard 59.984 - 60.008 (2.3616 - 2.3625)
0.03 (0.0012) US 59.962 - 59.978 (2.3607 - 2.3613)
0.05 (0.0020) US 59.942 - 59.958 (2.3599 - 2.3605)
0.25 (0.0098) US 59.742 - 59.758 (2.3520 - 2.3527)
Bearing size (Thickness at center) mm (in) #1, #3 Standard 1.998 - 2.015 (0.0787 - 0.0793)
0.03 (0.0012) US 2.017 - 2.020 (0.0794 - 0.0795)
0.05 (0.0020) US 2.027 - 2.030 (0.0798 - 0.0799)
0.25 (0.0098) US 2.127 - 2.130 (0.0837 - 0.0839)
#2, #4, #5 Standard 2.000 - 2.017 (0.0787 - 0.0794)
0.03 (0.0012) US 2.019 - 2.022 (0.0795 - 0.0796)
0.05 (0.0020) US 2.029 - 2.032 (0.0799 - 0.0800)
0.25 (0.0098) US 2.129 - 2.132 (0.0838 - 0.0839)
Thrust clearance mm (in) Standard 0.030 - 0.115 (0.0012 - 0.0045)
Oil clearance mm (in) Standard 0.010 - 0.030 (0.0004 - 0.0012)