The Subaru WRX STi engine legendary, but in large part because it’s been around for some time. The EJ257 2.5 liter turbocharged and intercooled four-cylinder boxer engine is virtually identical to the 300 horsepower EJ255 that first came to North America in 2004 in the WRX STi.
Today it’s rated at 305 horsepower and 290 pound-feet of torque on premium fuel which is still commendable, but less than competitive with newcomers like the Ford Focus RS which gets 350 horsepower out of its 2.3 liters.
Subaru enthusiasts of course will tell you 305 horsepower is just the baseline though, as this engine can be modded seven ways from Sunday to belt out 500 horsepower and more without a lot of brain damage, or loss in reliability.
That’s all good, but we’re talking about what is here an now. And that all starts with a pretty tightly packed engine compartment, with much of the turbocharger’s plumbing hidden away under the large top mounted air to air intercooler.
Following the airflow, the intake charge comes in through a large snorkel and into the air-filter box. It then travels up and then under the intercooler to the turbocharger mounted down underneath. Air then immediately goes to the cooler then into the engine through a red aluminum intake manifold, still made of aluminum.
The design makes for less turbo-lag with reduced plumbing that would be associated with a grill mounted intercooler. When max boost of 14.7 PSI is reached, a boost control valve lets extra pressure off right from the intercooler body.
Looking around the engine compartment reveals other retro touches like an electrically powered secondary air-pump that feeds fresh air into the exhaust system to water down emissions so it can pass smog. Most modern engine designs can make due with out one.
Also old school is the hydraulic power steering on the STi, not a bad thing. The belt driven pump does steal a little bit of power but delivers superior steering feel over most electric power steering systems.
One modern add to the WRX STi is the sound tube that channels acoustics from the intake tract directly into the passenger compartment, something you can really hear and feel almost to the point of annoyance at times. We’ve read some owners have pulled and chucked it.
The EJ257 still makes due with port fuel injection which is much easier to modify, and also has variable valve timing for both intake and exhaust cams.
Do it yourself servicing is something that many more owners of the WRX STi will do than most. And in such, service points are all well located and easy to find. Oil check and fill are up on top, the oil filter down under on the bottom of the engine.
The air-filter up front is accessible, but takes a little work to get to. Other fluids like windshield washer and coolant, brake fluid and power steering fluid also a no-brainer.
