Subaru Engine Swap Compatibility Chart (EJ/FA/FB Series)
Subaru’s legendary boxer engines have made the brand a favorite among enthusiasts for engine swaps, but the multiple engine generations (EJ, FA, FB) and diverse chassis platforms create a complex compatibility landscape. Whether you’re upgrading an Impreza, modernizing an older Legacy, or considering a turbo conversion, understanding which engines fit which chassis is essential for project success. This comprehensive compatibility chart covers every viable Subaru engine swap, from straightforward plug-and-play installations to complex custom projects.
As a Subaru specialist who has performed hundreds of engine swaps across all major engine families, I’ve learned that success comes from matching engines to chassis that share design philosophies, electrical architectures, and physical dimensions. What follows is not just a parts list, but a complete understanding of Subaru engine swap compatibility that will help you select the right path for your specific goals.
Subaru Engine Families Overview
EJ Series (1989-2014)
The EJ series powered Subaru for over 25 years across multiple platforms:
EJ Engine Types:
- EJ15/EJ18: 1.5L-1.8L naturally aspirated (early models)
- EJ20: 2.0L variants (NA and turbo)
- EJ22: 2.2L naturally aspirated
- EJ25: 2.5L variants (NA and turbo)
Notable Characteristics:
- Boxer layout (horizontally opposed cylinders)
- Single overhead cam (SOHC) or dual overhead cam (DOHC)
- Timing belt (not chain)
- Proven reliability with extensive aftermarket support
FA Series (2012-Present)
The FA series represents Subaru’s modern boxer engines:
FA Engine Types:
- FA20F: 2.0L direct-injection, naturally aspirated (BRZ/86)
- FA20DIT: 2.0L direct-injection, turbo (FA20F with twin-scroll turbo)
Notable Characteristics:
- Direct injection (DIT)
- Timing chain (improved over belt)
- D4-S boxer configuration
- More compact packaging than EJ series
FB Series (2010-Present)
The FB series introduced Subaru’s current-generation boxer engines:
FB Engine Types:
- FB16: 1.6L direct-injection (Levorg, Crosstrek)
- FB20: 2.0L direct-injection (Impreza, Forester, Legacy)
- FB25: 2.5L direct-injection (Legacy, Outback, Forester)
Notable Characteristics:
- Direct injection
- Timing chain
- Improved efficiency over EJ series
- Different mounting pattern than EJ/FA
Subaru Chassis Compatibility Matrix
Quick Reference Chart
| Chassis | Engine Series | Direct Fit | Minor Mods | Major Mods |
|---|---|---|---|---|
| GC/GF (1992-2000) | EJ15/EJ18/EJ20/EJ22 | EJ25 (mounts) | FA/FB (complete custom) | |
| GD/GG (2000-2007) | EJ20/EJ25 (all variants) | FA20 (BRZ swap possible) | FB (complete custom) | |
| GE/GH (2007-2011) | EJ20/EJ25 (all variants) | FA20 (BRZ swap possible) | FB (complete custom) | |
| GR/GV/GH (2008-2014) | EJ20/EJ25 (all variants) | FA20 (BRZ swap possible) | FB (complete custom) | |
| VA/VB (2011-Present) | FA20 only | EJ series (possible but complex) | FB (complete custom) | |
| SG (2007-2014) | FB20/FB25 (direct fit) | FA20 (minor mods) | EJ series (possible but complex) | |
| SJ (2014-Present) | FB20/FB25 (direct fit) | FA20 (minor mods) | EJ series (complex) |
Direct Fit Swaps (Easy)
EJ20 Turbo to GD/GG/GE/GH/GR/GV/GH Chassis
Best For: Upgrading naturally aspirated Impreza/WRX to turbo power
Compatibility:
- Chassis: GD (2000-2007), GG (2007-2011), GE/GH (2007-2011), GR/GV/GH (2008-2014)
- Transmission: Uses factory transmission (5-speed or 4-speed auto)
- ECU: Can retain with appropriate tune or upgrade to aftermarket
Popular EJ20 Turbo Options:
| Engine | Power | Torque | Source | Notes |
|---|---|---|---|---|
| EJ205 (WRX 2002-2005) | 227 hp | 217 lb-ft | WRX donor easiest | |
| EJ255 (WRX 2006-2007) | 230 hp | 235 lb-ft | Slightly more power, later WRX | |
| EJ207 (STI 2004-2007) | 280 hp | 300 lb-ft | Semi-closed deck, preferred | |
| EJ207 (STI 2008+) | 300 hp | 300 lb-ft | Full closed deck, strongest |
Required Components:
- Engine mounts (usually direct fit) - $0-200
- Wiring harness (may need ECU pin changes) - $150-400
- Exhaust system (turbo requires different routing) - $300-700
- Intercooler piping (if not already equipped) - $200-500
- Fuel system (higher flow pump may be needed) - $100-300
Estimated Total Cost: $750-2,100 (DIY), $1,500-3,500 (professional)
Performance Gains:
- Stock EJ20 NA (165 hp): +62-135 hp gain
- Stock EJ25 NA (165 hp): +62-135 hp gain
EJ25 Turbo to GD/GG/GE/GH/GR/GV/GH Chassis
Best For: Significant power increase for older Impreza/Forester/Legacy
Compatibility:
- Chassis: GD/GG/GE/GH/GR/GV/GH (2000-2014)
- Transmission: Uses factory transmission with potential for upgraded clutch
- ECU: Can retain with proper tune or upgrade
Popular EJ25 Turbo Options:
| Engine | Power | Torque | Source | Notes |
|---|---|---|---|---|
| EJ255 (Forester XT) | 210-224 hp | 235-250 lb-ft | Most common, widely available | |
| EJ257 (STI) | 280-300 hp | 300-300 lb-ft | Premium option, strongest |
Required Components:
- Engine mounts (may require slight modification) - $100-300
- Wiring harness adaptation - $200-500
- Exhaust system (custom fabrication required) - $400-800
- Intercooler (larger than NA setup) - $300-600
- Fuel system (upgrade pump recommended) - $150-400
Estimated Total Cost: $1,150-2,600 (DIY), $2,000-4,500 (professional)
Performance Gains:
- Stock EJ25 NA (165 hp): +45-135 hp gain
- Torque Improvement: +70-135 lb-ft
FB20 to SG/SJ Chassis (Direct Fit)
Best For: Modernizing older Forester/Crosstrek with current-generation engine
Compatibility:
- Chassis: SG (2007-2014 Forester), SJ (2014+ Crosstrek/Forester)
- Transmission: Uses factory transmission
- ECU: Can retain with appropriate programming
FB20 Specifications:
| Specification | FB20 |
|---|---|
| Displacement | 2.0L |
| Power | 145-152 hp (depending on model) |
| Torque | 145-148 lb-ft |
| Induction | Direct injection |
Required Components:
- Engine mounts (direct fit) - $0-100
- Wiring harness (may need ECU adaptation) - $150-350
- Exhaust system (direct fit to chassis) - $300-500
- Cooling system (verify compatibility) - $100-300
Estimated Total Cost: $550-1,250 (DIY), $1,000-2,000 (professional)
Semi-Direct Swaps (Moderate)
FA20 (BRZ/86) into GD/GG/GE/GH Chassis
Best For: Modern high-revving naturally aspirated engine in older chassis
Compatibility:
- Chassis: GD (2000-2007), GG (2007-2011), GE/GH (2007-2011)
- Transmission: Requires transmission swap (BRZ/86 transmission)
- ECU: Standalone ECU mandatory (FA20 uses CAN bus)
FA20 Specifications:
| Specification | FA20F (BRZ/86) |
|---|---|
| Displacement | 2.0L |
| Power | 200 hp |
| Torque | 151 lb-ft |
| Induction | Port/Direct injection |
| Redline | 7,400 rpm |
Required Components:
- Custom engine mounts - $300-600
- Transmission swap (BRZ/86 trans to GD/GG/GE/GH) - $600-1,200
- Custom axles - $400-800
- Standalone ECU (Haltech, AEM, or Motec) - $1,200-2,000
- Custom exhaust system - $500-900
- Complete wiring harness fabrication - $600-1,000
Estimated Total Cost: $3,600-6,500 (DIY), $5,500-9,000 (professional)
Performance Gains:
- Stock EJ20 NA (165 hp): +35 hp gain
- Stock EJ25 NA (165 hp): +35 hp gain
- Advantage: Higher redline, more modern engine design, better reliability
EJ25 into VA/VB Chassis (BRZ/86)
Best For: Adding torque to BRZ/86 with proven reliability
Compatibility:
- Chassis: VA (2011-2016), VB (2017+)
- Transmission: Uses factory transmission (6-speed)
- ECU: Standalone ECU mandatory (different CAN bus)
Required Components:
- Custom engine mounts - $400-800
- Transmission adapter (if different transmission used) - $300-600
- Standalone ECU (Haltech Elite 2500, etc.) - $1,200-2,000
- Custom exhaust system - $500-900
- Complete wiring harness fabrication - $600-1,000
- Cooling system upgrade (EJ25 runs hotter) - $200-400
Estimated Total Cost: $3,200-5,700 (DIY), $5,000-8,500 (professional)
Performance Gains:
- Stock FA20 (200 hp): +30-65 hp (EJ25 turbo)
- Torque Gain: +50-149 lb-ft (EJ25 turbo)
- Trade-off: More weight, less high-RPM capability
Custom Swaps (Advanced)
FA20DIT Turbo (Levorg/WRX STI) into Any Chassis
Best For: Ultimate modern turbo power with direct injection
Compatibility:
- Chassis: All Subaru platforms with extensive modification
- Transmission: Requires appropriate 6-speed (CVT or 6MT)
- ECU: Standalone ECU mandatory
FA20DIT Specifications:
| Specification | FA20DIT |
|---|---|
| Displacement | 2.0L |
| Power | 271-296 hp (depending on model) |
| Torque | 258-310 lb-ft |
| Induction | Twin-scroll turbo, direct injection |
Required Components:
- Complete custom engine mounts - $500-1,000
- Transmission solution (complete swap likely) - $1,000-2,000
- Standalone ECU (Haltech, Motec, Syvecs) - $2,000-3,500
- Custom exhaust system (full fabrication) - $800-1,500
- Complete wiring harness - $800-1,500
- Fuel system upgrade (high-pressure DIT pump) - $300-600
- Cooling system (larger radiator, intercooler) - $500-1,000
- Drivetrain components (custom axles, driveshaft) - $600-1,200
Estimated Total Cost: $5,500-9,300 (DIY), $9,000-15,000 (professional)
Performance Gains:
- Stock EJ20 NA (165 hp): +106-131 hp gain
- Stock FA20 (200 hp): +71-96 hp gain
- Advantages: Modern technology, twin-scroll turbo, direct injection efficiency
FB25 Turbo into Older Chassis
Best For: High-torque, modern engine in legacy chassis
Compatibility:
- Chassis: GD/GG/GE/GH/GR/GV/GH (2000-2014) with extensive modification
- Transmission: Requires appropriate 5-speed or CVT
- ECU: Standalone ECU mandatory
Required Components:
- Complete custom engine mounts - $600-1,200
- Transmission solution - $1,000-2,000
- Standalone ECU - $2,000-3,500
- Custom exhaust system - $800-1,500
- Complete wiring harness - $800-1,500
- Fuel system upgrade - $400-800
- Cooling system - $600-1,200
- Drivetrain components - $800-1,500
Estimated Total Cost: $6,600-10,200 (DIY), $10,500-18,000 (professional)
Performance Gains:
- Stock EJ25 NA (165 hp): +75-135 hp gain
- Torque Improvement: +105-175 lb-ft
Subaru Engine Swap: Complete Compatibility Matrix
By Engine Family
| Engine Family | Best Target Chassis | Difficulty | Estimated Cost (DIY) |
|---|---|---|---|
| EJ20 Turbo | GD/GG/GE/GH/GR | Easy | $750-2,100 |
| EJ25 Turbo | GD/GG/GE/GH/GR | Easy-Moderate | $1,150-2,600 |
| EJ25 NA | GD/GG/GE/GH/GR | Easy | $500-1,000 |
| FA20 (NA) | GD/GG/GE/GH | Moderate | $3,600-6,500 |
| FA20DIT | Any chassis | Difficult | $5,500-9,300 |
| FB20/FB25 | SG/SJ (direct), others (custom) | Moderate-Difficult | $2,000-10,200 |
By Chassis Type
| Chassis | Best Engine Options | Easiest Swap | Hardest Swap |
|---|---|---|---|
| GC/GF (1992-2000) | EJ20/EJ22 NA | EJ20 NA | FA/FB series |
| GD/GG (2000-2007) | EJ20/EJ25 (all variants) | EJ20 Turbo | FA20DIT |
| GE/GH (2007-2011) | EJ20/EJ25 (all variants) | EJ20 Turbo | FA20DIT |
| GR/GV/GH (2008-2014) | EJ20/EJ25 (all variants) | EJ25 NA | FA20DIT |
| VA/VB (2011+) | FA20 only (direct), EJ25 (custom) | FA20 | FA20DIT |
| SG/SJ (2007+) | FB20/FB25 (direct), FA20 (minor) | FB20 | EJ series |
Transmission Compatibility
Transmission Families by Engine
| Engine | Compatible Transmissions | Notes |
|---|---|---|
| EJ20 NA | 5-speed MT, 4-speed AT | Direct fit |
| EJ20 Turbo | 5-speed MT, 4-speed AT | May need clutch upgrade |
| EJ25 NA | 5-speed MT, 4-speed AT | Direct fit |
| EJ25 Turbo | 5-speed MT, 4-speed AT | Heavy-duty clutch recommended |
| FA20 | BRZ/86 6-speed MT, CVT | Transmission swap required for older chassis |
| FA20DIT | Levorg CVT, 6-speed MT | Complex for swaps |
| FB20 | Lineartronic CVT, 6-speed MT | Generally requires CVT/MT swap |
| FB25 | Lineartronic CVT, 6-speed MT | Generally requires CVT/MT swap |
ECU and Tuning Solutions
Standalone ECU Options
| ECU System | Price | Compatible Engines | Feature Set |
|---|---|---|---|
| Haltech Elite Series | $1,200-2,500 | All Subaru engines | Advanced features, excellent support |
| AEM Infinity | $1,000-1,800 | EJ/FA series | Comprehensive, CAN integration |
| Motec M800 | $2,000-3,000 | EJ/FA/FB series | Premium option, motorsports-grade |
| Cobb Accessport | $600-1,000 | EJ series (flashing) | Plug-in tuning |
| OpenSource ECU | $400-800 | Most engines | DIY, limited support |
ECU Programming by Engine Type
| Engine Type | Recommended ECU | Programming Difficulty |
|---|---|---|
| EJ Series | Haltech, AEM, Cobb | Moderate |
| FA20 | Haltech Elite 2500, Motec | Difficult (CAN bus) |
| FA20DIT | Haltech Elite 2500, Motec M142 | Very Difficult (complex CAN) |
| FB Series | Haltech Elite 2500, Motec M142 | Very Difficult (complex CAN) |
Required Components Breakdown
Engine Mounts by Swap Type
| Swap | Required Mounts | Cost |
|---|---|---|
| EJ to EJ (same chassis) | Stock | $0-200 |
| EJ to FA | Custom | $300-600 |
| EJ to FB | Custom | $500-1,200 |
| FA to EJ (VA/VB) | Custom | $400-800 |
| FA20DIT to any | Complete custom | $500-1,000 |
Exhaust Systems
| Swap | Exhaust Requirement | Fabrication |
|---|---|---|
| EJ to EJ (NA to Turbo) | Different routing, larger diameter | Moderate |
| EJ to FA | Complete custom | Extensive |
| FB to SG/SJ | Direct fit | Minimal |
| FA to any chassis | Complete custom | Extensive |
Cooling Systems
| Swap | Cooling Requirements |
|---|---|
| NA to Turbo | Larger radiator, intercooler required |
| EJ to FA/FB | May need larger radiator |
| FA20DIT | Significant cooling upgrades required |
| FB25 Turbo | Major cooling system upgrades required |
Legal and Emissions Considerations
US Emissions Compliance
| Engine Swap | Emissions Status | Notes |
|---|---|---|
| EJ20 NA to EJ20 Turbo | Generally compliant | Same displacement, different induction |
| EJ25 NA to EJ25 Turbo | State-dependent | Turbocharger requires additional inspection |
| EJ to FA/FB | State-dependent | Different engine family, complex approval |
| FA20 to EJ25 | State-dependent | Different displacement, older engine |
Important: Always verify local regulations. Some states (CA, NY) have strict requirements about engine swaps within certain displacement ranges and emission standards.
Registration and Documentation
- Registration: Must update vehicle title with engine displacement and number of cylinders
- Insurance: Notify insurer of modifications (may affect premiums significantly)
- Documentation: Keep all receipts, engine codes, and ECU programming records
Frequently Asked Questions
What’s the easiest Subaru engine swap?
EJ20 turbo into GD/GG chassis is the easiest—essentially plug-and-play with proper donor engine and minor wiring modifications.
Can I put an FA20 (BRZ/86) engine in an older Impreza?
Yes, but it’s a moderate difficulty swap requiring transmission swap, custom mounts, standalone ECU, and extensive wiring. Expect $3,600-6,500 (DIY).
Is a Subaru STI engine worth swapping into a regular WRX?
Yes and no. EJ207/EJ257 STI engines offer significant power (+50-70 hp), but are expensive ($2,500-4,000 for engine alone) and may not be cost-effective compared to turbocharging stock engine.
What’s the difference between EJ257 and FA20DIT engines?
EJ257 is an older turbo engine (280-300 hp) with port injection, while FA20DIT is a modern twin-scroll turbo engine (271-296 hp) with direct injection, better efficiency, and more advanced technology.
Can I swap an FB engine into a BRZ/86?
Yes, but difficult. FB engines have different mounting and require extensive custom fabrication. EJ25 swaps are more common and easier.
Do I need to change my transmission when swapping Subaru engines?
Depends on swap:
- EJ to EJ (same chassis): Often uses existing transmission
- FA20 to older chassis: Requires transmission swap (BRZ/86 transmission)
- EJ to FA chassis: Requires transmission adaptation or swap
- FA20DIT/FB25 Turbo: Usually requires complete transmission solution
How much does a Subaru engine swap cost?
Varies widely:
- Direct EJ swaps: $750-2,600 (DIY)
- FA20 swaps: $3,600-6,500 (DIY)
- FA20DIT swaps: $5,500-9,300 (DIY)
- FB25 turbo swaps: $6,600-10,200+ (DIY)
Professional installation typically adds 50-100% to DIY costs.
Which Subaru engines have the best aftermarket support?
EJ20/EJ25 series have the most extensive aftermarket support—decades of performance parts, tuning solutions, and community knowledge. FA/FB series have growing support but less mature.
Conclusion: Choosing Your Subaru Engine Swap
Subaru engine swapping offers incredible flexibility for performance upgrades, from straightforward EJ turbo conversions to complex FA20DIT projects. The right choice depends on your chassis, budget, fabrication skills, and performance goals.
Our Top Recommendations:
- Best Overall: EJ205/EJ255 (WRX) into GD/GG chassis - Proven reliability, easy installation, excellent power gains
- Best Value: EJ20 NA to EJ20 Turbo - Cost-effective, straightforward, significant gains
- Best Modern: FA20 into older chassis - Modern engine design, high-revving capability, moderate complexity
- Best Power: FA20DIT into any chassis - Ultimate performance, twin-scroll turbo, direct injection, significant complexity
- Best for BRZ/86: EJ25 NA - Proven torque improvement, reasonable complexity, good reliability
Engine swapping a Subaru is a significant undertaking that requires proper planning, quality components, and realistic expectations about fabrication complexity. However, when executed correctly, a well-swapped Subaru delivers performance, reliability, and driving engagement that stock configurations simply cannot match.
All specifications and costs reflect 2026 market data. Owners should verify local regulations and consult professional fabricators before attempting complex swaps.
