Power Pages: 2002 Subaru WRX

It was only a matter of time before we got our hands on a 2001 WRX Subaru for a Power Pages session. The popularity of this vehicle is growing and the call to the aftermarket has been made. Our Subaru will undergo a series of Power Pages hop ups to realize the true potential of the EJ20G engine. We will first start out with the basics, then move on to bigger components.

The Engine
The flat four, better known as Boxer, engine is not like your normal internal combustion engine. This engine relies on the number one and two cylinders on the driver side and the three and four cylinders on the passenger side, with all four pistons horizontally opposed. This configuration calls for two separate dohc cylinder heads. The Subaru's Boxer engine generates 227 hp and 217 lb-ft of torque in turbocharged trim. This horsepower level is produced at 13.5 psi of boost. A big 92mm bore and 75mm stroke allow the engine to redline at 7000 rpm.

Performance Components
Given that the car is new to the market, we figured it might be difficult to locate aftermarket components for the test, but it turns out that XS Engineering needed a guinea pig vehicle to test out some of their latest WRX products. Incorporated in the build up is an XS Engineering cold air intake, XS cat back exhaust system and an APEXi S-AFC.

The air intake is constructed of polished aluminum and removes the need of the OE mass air housing. Incorporated into the intake is a billet aluminum flange made to except the OE hot wire unit. The intake system replaces and relocates the air filter into the passenger side fender, giving the engine plenty of cool air to ingest. The filter is a conical open-element type using a 3-in. outlet to the intake pipe.The XS exhaust system is 3-in. mild steel with a stainless canister tip measuring 4.5 in.

One component that isn't new to Power Pages is the APEXi Super Air Flow Converter, which is designed to control fuel tuning at almost any given rpm range. This not only makes a good upgrade for part one of our Power Pages WRX tests, but it will also play a key role in several upcoming tests. APEX is currently working on a Power FC for the WRX, but it will not be available until the middle of 2002. At that time, the WRX Power FC will be available from your local APEX Power Excel dealers.

Dyno Testing
With the WRX being AWD, we are forced to step away from the Dynojet dyno and move on to a dyno capable of handling an all-wheel drive vehicle. We enlisted the help of a Dynapack dynamometer since it is worthy of handling the task. Not only is the unit easy to use, numbers are just as accurate, if not more so, than other units on the market.

Baseline testing began at 168.8 hp to the wheels, which might seem far off, but remember that we're testing this power at all four wheels, so this tells us that this power level, after drivetrain losses, is plenty for a baseline figure. Torque levels registered at 164.8 lb-ft.

Installing the XS filter system required very little modification. The unit we are testing is their prototype piece, but the production piece is identical to the prototype unit--in polished trim. It provided for a noticeable difference in power at the mid and top end of the graph. A gain of 8 to 13 hp was found, providing for a peak of 182.7 hp.

The XS exhaust is a complete bolt-on system. Considering the OE unit measures 2.25-in. and the XS piece is 3, we can guess there will be plenty of power released. On the Dynapack the WRX generated an additional 3 to 5 hp throughout the graph and a 5.2 hp gain in the peak section of the graph. The torque figure was also increased to 187.2 lb-ft.

Even before any product was installed on the WRX, we ran an air/fuel meter during our baseline pass which showed the car running a very rich 10.5 ratio in stock trim. With the air filter and exhaust installed there was definitely going to be some tuning involved with the AFC unit. After tweaking the AFC, our air/fuel mixture was still rich in order to keep detonation low, but the AFC was able to produce a gain of 2.7 hp and .4 lb-ft of torque over our previous run. What we discovered is fuel tuning is a necessity in the first stage of making more power in the WRX.

Conclusion
In our first part of Power Pages WRX we locked in a total of 21.8 hp over stock and 22.8 lb-ft of torque over our baseline figures. In our second round we plan on bringing up the turbo boost levels, as well as tinkering more with the exhaust flow.

The Facts
The Car: 2002 Subaru WRX
The Owner: Import Tuner
Engine Tested: EJ20G
Applications: None
Common Swaps: None
Replacements: None

The Parts
XS Engineering Intake System $185
XS Engineering Exhaust $495
APEXi Super AFC $429
MSRP $1109