My Objective

  1. counter the effect of altitude (Calgary is at 4,000 feet above MSL, and air pressure is 2 PSI lower)
  2. lower the RPM at which peak torque is obtained
  3. increase horsepower by about 20% (150 engine HP is the goal, up from 130HP stock)
  4. high reliability
  5. low cost
  6. the same or better fuel economy

The Plan

My engine is the stock EJ22 16valve SOHC engine which produces 130HP at 5,500RPM and 137lb/ft of torque at 4,400RPM. If RPM's are kept above 2,500 RPM the engine is quite responsive. From a standing start, acceleration to 100KPH takes about 10 seconds flat, acceleration when moving in 2nd gear is quite good.

Do to my requirement of high reliability and good fuel economy I am ruling out turbocharging and supercharging. While all Subaru engine blocks are much stronger than the majority of other manufacturers, they do have their limits.

Car and Driver just blew up a Rimmer Supercharged engine in a 2.5RS. The engine self-destructed due to oil starvation. The engine was overdue for an oil change and was also low on oil. The engine blew when the car was cornering at 138MPH on the Ford test track in Michigan, due to the G force the oil moved to one side of the oil pan resulting in air being picked up by the oil pump siphen. The lack of oil and the higher operating temperatures due to the extra power led to the engine failure. While the Rimmer Supercharger was not the cause of the failure, it was a secondary contributing factor (higher operating temperature).

Subaru engines (turbo or not) do have one significant problem. Due to the design of the fuel rail, it is possible to cause fuel starvation to the number 1 cylinder. Many WRX's have blown engines due to this defective design. The use of a fuel pressure riser and higher flow fuel pump can solve this problem.

If you plan on supercharging or turbocharing your Subaru, please use an external fuel controller (such as a Field Hyper SFC) and a fuel pressure riser.

I do not want the complication or risk and do not need high horsepower, so I will avoid turbo and superchargers altogether.

There are two ways I am going to increase power to the wheels:

  1. increase the amount of air into the engine (more air = more fuel = more power)
  2. decrease parasitic loads on the engine

Increasing the air into the engine is a two step process:

  1. home made 3" air intake tube
  2. use a K&N cone filter
  3. install an electric turbocharger such as the Turbo-Zet or E-Ram

Decreasing the parasitic load on the engine:

  1. install a Unorthodox Racing underdrive pulley
  2. use high quality engine, transmission and differential lubricants
  3. use Redline Water Wetter to keep engine temperatures in check
  4. install an aftermarket catalytic converter and muffler, I am considering the MRT kit.

Current Status

  1. air intake tube and air filter are installed
  2. using Mobil 1 10w30 engine oil year round
  3. using Castrol Syntec 75W90 GL5 in the transmission and rear differential
  4. using Castrol Syntic Dexron III in the power steering system

The Results

Air intake tube and air filter dropped the 0 to 100KPM time from 10 seconds to 9.6 seconds. Engine horsepower is up by 7 HP to 137HP.

Engine is loud at full open throttle, I will need to add sound insulation under the hood to compensate for this.

Very nice sound at mid throttle.