Subaru Motor Matrix

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Here's a handy chart for Subaru's EJ 2.5L motor.  This chart shows what you "generally" need to put on your shopping list to build a reliable motor based on the horsepower range you want to achieve.  It's important to know the limits of your motor setup so you buy the right equipment, using the right motor core that's compatible for potential future upgrades.

"A man's gotta know his limits........... well do ya punk?"   Clint Eastwood, Dirty Harry

HP ~200HP ~270HP ~330HP ~400HP ~450HP
2.5L Subaru Stock Motor DOHC or SOHC Stock Motor DOHC or SOHC Stock Motor DOHC or SOHC Upgraded deck and Internals on DOHC or SOHC Upgraded deck and Internals on DOHC motor
Exhaust Turbo compatible exhaust (no turbo) Outfront Std jet coated Exhaust for T-3 Turbo Outfront Super flow setup for external wastegate for T-3 Outfront Super flow setup for external wastegate for T-3 Outfront Super flow setup for external wastegate for T-3
Computer EMS Stinger EMS Stinger EMS Stinger EMS8860 or Motec EMS 8860 or Motec
Fuel 91 octane 105 octane 110 Octane 110 Octane 110 Octane
Turbo None OE Subaru Turbo T3/T4 Turbo with external waste gate T3/T4 with external waste gate T-25 ball bearing with external waste gate
Waste Gate None Internal with OE turbo External gate with supported exhaust flange External gate with supported exhaust flange External gate with supported exhaust flange
Boost setting None 7-8lb for 270 10lbs max 15-17 lbs 20 lbs
Intercooler None None
 
Outfront intercooler with scoop Outfront intercooler with scoop and blow off valve Outfront intercooler with scoop and blow off valve
Engine Block Stock Stock, if the boost  is set to <10lbs Stock, if the boost  is set to <10lbs Outfront closed deck block Outfront closed deck block
Rods Stock Stock, if the boost  is set to <10lbs Stock, if the boost  is set to <10lbs Outfront racing rods Outfront racing rods
Pistons Stock Stock, if the boost  is set to <10lbs Stock, if the boost  is set to <10lbs JE Racing Pistons JE Racing Pistons
Ignition Stock Stock, if the boost  is set to <10lbs Stock, if the boost  is set to <10lbs Hi Output ignitor Hi Output ignitor
Fuel system Stock injectors, fuel rails, and regulator Stock injectors with Bosch fuel regulator. New injectors and fuel rails are recommended Outfront billet fuel rails, Bosch 50lb injectors, Bosch fuel regulator Outfront billet fuel rails, Bosch 50lb injectors, Bosch fuel regulator Outfront billet fuel rails,  Bosch 72lb injectors, Bosch fuel regulator
Blowoff Valve none Stock blow-off valve for OE turbo None Tial Tial

A little insight on motor selection in the beginning can help you make the right choices before you buy your motor core.  The above chart talks about 2.5L motors because it's the most popular.  Here's a summary with more info on various Subaru displacements.

2.0L motors:  This motor is a good choice for the budget minded if making a 2 seat car.  With the right modifications you can pump up to 300HP out of this engine, great for a light car that weighs less than 1300lbs.  JDM used motors can be bought for $1000 to $1500 depending on the version, year, and condition.

2.2L motors:  The factory 2.2 turbo is a strong foundation for a motor package. The non turbo 2.2 is John's least favorite motor (for horse power)the non turboed version should not be turboed over 5 psi, and it needs injectors to add the turbo for adequate fuel delivery.

2.5L motors:  This motor is the most popular by far, primarily because of the possibilities to build upon the incredible infrastructure of the engine to build a motor from 200HP to 600HP.  JDM motor cores can be bought for $1500 to $2000 depending on the year, type, and condition.  The DOHC non turbo versions come in cars from 1996 to 1998 and are very plentiful.  DOHC versions have larger intake manifolds than later model  SOHC versions for slightly better flow.  SOHC motors come in midrange Subaru automobiles from 1999 to present.  These versions have slightly better low end torque.  If you're targeting a mild 300HP engine these later model SOHC motor with stock injectors will usually suffice. 

3.0L motors:  These 6 cylinders motors are gaining in popularity.  They weigh about 75lbs more than a 2.5L motor with 4 cylinders, and they are only 1.5" longer too.  This is perfect for sandrail applications, especially if you want to use 91 octane fuel while being over 75lbs lighter than a Honda 3.2L or 3.5L.

3.3L motors:  These 6 cylinder motors are about the same weight as a Honda 3.2 motor.  But they offer a much lower center of gravity with the boxer style motor, like all Subaru motors.  Originally used in Subaru's high end SVX sports car, this  3.3L offers lots of low end torque and runs naturally aspirated on 91 octane fuel to deliver a great performing budget motor with over 240HP.  These motors are not recommended for turbo charging.  It's better to use the 3.0L if a turbo motor with race gas is in your future.