Zzyzx Motorsports Impreza 2.5 RS - engine modification list

September 26, 2005

To keep the Subaru community informed of what we've done to break the 300 HP mark for a naturally aspirated 2.5L Subaru Flat-4 as outlined in our previous press release, we're including a list of modifications that helped get us there. Please understand, however, that not every detail is or will be disclosed about this engine as we feel it's inappropriate to do all the ground work, then give the entire receipe to those that didn't put in the time, money and effort it takes to achieve such results.

Mod list:

• Subaru OEM 2005 2.5 RS spark plug wires
• Subaru OEM 2005 2.5 RS coilpack
• Subaru OEM 2005 2.5 RS fuel rail
• Subaru OEM 2005 2.5 RS intake manifold
• Subaru OEM 2003 WRX fuel injectors
• NGK BKR6E-11 V-power spark plugs (copper)
• Accufab 65mm Ford Mustang throttle body
• TWE Stage III heads
• TWE Stage II SOHC street cams
• TWE 100mm 11.2:1 CR forged pistons
• TWE 4-2-1 race headers (large primaries)
• TWE 2.5" catless race pipe
• TWE 2.5" midpipe
• 255 LPH Walbro fuel pump
• Aeromotive fuel pressure regulator
• Link Electrosystems LinkPlus engine management
• 108 Octane race gas
• No muffler
• No air filter - open throttle body

Misc:

• Idle air control is achieved using a Ford OEM IAC solenoid.
• Throttle position sensor on TB is Ford OEM.
• Throttle linkage was custom fabricated by Zzyzx Motorsports.
• Adapter plate to bolt Accufab 65mm TB to intake manifold custom fabricated by TWE.
• Engine oil is Motul 300V 15-50.
• Transmission and rear diff oil is Redline Shockproof Lightweight (smurf blood).

Tuning:

• All tuning was done by Jake Diehl at Dieman Motorsports in Lees Summit, MO.
• The dyno is an MD Mustang IMP dynomometer.