Before we look at engine modifications I ask you take the time to understand where we are coming from. I know of several owners who want to go real fast. They want the best power possible and will listen to the person who talks the highest power numbers. They are buying all kinds of blow-off valves, front mount intercoolers, big turbos and large bore exhuasts thinking all this is going to give them 300hp at the wheels. This is just not the way to go. We can properly tune the US WRX engine to run very hard on 91 to 94 octane gas with only minor physical changes to the engine.

There seems to be a great deal of confusion about what engine we have. As mentioned in the WRX intro engine section, we have a similar model EJ205 rated at 250hp in Japan on "96" octane gas, but without the Japanese variable valve timing. This is not a 280hp engine that is detuned nor is it the STI forged piston version. I cannot stress enough the limitations of our 91-93 octane gas in a turbo motor. We are power limited by our fuel. Taking this into account and factoring our 91 octane fuel into the picture we have taken a conservative approach to engine tuning at this time. Cheat the devil at you own risk.

There have also been issues with intake kits setting of codes on the motor, at which time you friendly vendor will want to sell you a fuel mixture adjustor. If we attack the power problem as one of tuning the turbine by exhaust changes this will not occur.

Just release in spring 2003 are several ECU ROM upgrade kits. This is the way to go. We have chosen to sell the Prodrive kits because we are convinced  they have had the best testing program and the best software program. The ECU is a variable setting 'state machine' that uses a complex set of tuner adjustable target values and tuning adjustable rules to give the best power and throttle response for a given fuel octane and atmospheric conditions. It learns and adjusts as the engine runs.

The Prodrive kits have the benefit of factory help in telling them where "All the bodies are buried" in the tuning tables of this ECU. The subtle adjustments they have made in many interactive areas of the ECU are well beyond what the competition can possibly do. It shows in drivability at part throttle and below 4000 rpm as much as it does in the smooth power delivery. Anyone can get more power, but to get more power with great drivability is what we are selling. I would think that anyone tuning this engine would be able to get similar results, but that is not quite true. 

I have been asked not to give all the details for tuning the Impreza, but Prodrive is the only company that has separately tuned for 2002 or 2003 and automatic or manual transmission. This is a clue that they into a greater level of detail in their tuning methods than other companies.

The three stage kits are additive, starting with low rpm torque and throttle response improvements

Stage one is a Prodrive muffler and the ECU upgrade. Huge torque increases below 4000 rpm and much improved throttle response at low rpm. The 4000-6000rpm power is also greatly improved.

Stage two is the addition of the third cat eliminator and a slight change in mixture and timing so that the 4000-7200 power range is also greatly improved.

Stage three has these three essential additions: A stainless matrix down pipe cat, a special up-pipe and a compressor discharge Y-pipe replacement. The boost target, timing targets and fuel targets are all changed to let the stock turbocharger run at is maximum flow rate. A given turbocharger maximum flow rate is limited not by its rotational speed as one would think. It is limited first by the air mass flow heating up too much beyond a certain boost level. It looses it thermal efficiency. Boost can go up, but power does not.  The 91-93 octane fuels we get limits the boost we can run. The Stage three is running the turbo at optimum discharge heat values and that plays into running optimum relationship between boost levels and timing values.  The Prodrive kits are able to get more power with less thermal stress by having carefully tested and programming for these optimum relationships.

Note that each of these kits have a quoted dyno wheel horsepower. Your results will vary from this depending on the atmospheric conditions and the octane fuel being used. With the Prodrive kit you are assured that the motor is making the maximum safe power for the CAT setup being run at all times. We are tuning the ECU to have the highest target values for boost and timing. It then decides all by itself just how much power will be safe for the motor.

These kits require special installation of the ROM software. Contact SPD Tuning for details.