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:
Increasing the air into the engine is a two step process:
Decreasing the parasitic load on the engine:
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.