In the first part of our Power Pages WRX we explored the effects of adding an air intake, exhaust and fuel tuning. We learned that the WRX in stock trim runs a very rich 10.4:1 air/fuel ratio, and getting the engine to breath easier has a big effect in the horsepower department. So far we have also learned that the water boxer engine is not too difficult to enhance with bolt-on components. As the cylinder heads are parallel with the vehicle's frame, we will soon discover how difficult it is to play with different camshaft profiles in an upcoming segment.
The EngineWith the addition of the XS Engineering air intake, exhaust and A'PEXi AFC we found an additional 21.8 hp and 22.8 lb-ft of torque. This round we go deeper into the power within the EJ20's turbocharger. The factory unit is an IHI pumping out a maximum boost pressure of 11 psi. Its size is very deceiving; it may look small, but this baby was able to put out an incredible 190 hp at the end of our last session.
Performance ComponentsSince the vehicle is already equipped with an air intake, exhaust system and fuel computer, it was time to see what the stock turbo was capable of producing. The turbo has already been given some breathing room with the above mentioned components, so we decided to open up the exhaust system even more with an XS Engineering front pipe/mid pipe comb while upping the boost level to 15 psi using an A'PEXi AVC-R boost controller.
The mid pipe is offered with a 2.75-in. tubing diameter. The bolt-on unit is constructed of 16-gauge mild steel to take on the extreme heat produced by the turbocharger. All the bolt-on flanges are made of 3/8-in. steel, and the factory O2 sensor bung compliments the factory location for the sensor. This unit also removes the second catalytic converter in the three-cat system.
Just like the XS Engineering front pipe, the mid pipe removes one of the OEM catalytic converters, leaving only the first cat out of the three left in the exhaust system. This unit is also constructed of 16-gauge mild steel and 3/8-in. flanges. To ease operating stress on the pipe, XS incorporated a flex pipe to take on the engine's movement.
Another valuable power-producing component, not new to Power Pages, the A'PEXi AVC-R boost controller will play an important role in upping the factory boost levels on the WRX. With so many options built in to this unit, we're able to control boost by the change of gears, speed and engine rpm. The AVC-R can also be used as a textbook boost controller, which is exactly how we used it on this test vehicle.