Driven: 2015 Subaru WRX

Driven: 2015 Subaru WRX

by Khiem Dinh

Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing.  All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.

At the heart of the big change is the new FA20DIT lump sitting under the hood with the ancient EJ finally being put out to pasture; well, at least in the WRX. The STI still soldiers on with the EJ25. Anyway, the FA20DIT is fundamentally different than the EJ20/25 in the turbocharger configuration. The twin-scroll turbo is mounted down low and at the front of the engine bolted to a practically equal length manifold (so the old EJ rumble is gone). The FA20 is also uses direct fuel injection following the trend of the modern gasoline engine.

 

Here is a cutaway of the FA20DIT we showed you back in 2012 at the LA Auto Show.

Those of you who know Subarus know the name Perrin. The guys at Perrin did some nice testing of the 2015 WRX and STI with some data comparing them to a 2008 STI. You can read Perrin’s full report here (http://blog.perrinperformance.com/2015-sti-and-wrx-dyno-time/). Below is one of the plots in Perrin’s report showing the torque curves of the 2015 WRX vs. STI.

 

One reason I prefer the WRX to the STI for a daily driver is the more useable torque curve. Despite the FA20DIT only being 2.0L vs. the STI EJ25 at 2.5L, the direct injection and twin-scroll turbo of the FA20DIT has the torque come on about 500rpms sooner than its older and larger sibling. Check out the rest of Perrin’s testing here: http://blog.perrinperformance.com/wp-content/uploads/2014/05/2015_stiwrxhp.jpg

When you read through Perrin’s blog post, take note of the 2015 WRX torque and power curves vs. the 2008 STI. The 2015 WRX torque comes on a smidge earlier compared to the 2008 STI and the WRX also carries that torque and power advantage all the way to 6250rpms or so. It’s amazing that modern technology allows a 20% smaller engine to essentially perform as well as the older and bigger engine.

I recently had the opportunity to take a 2015 WRX equipped with the CVT tranny on a road trip of a few hundred miles. I wasn’t sure what to expect with the CVT, but let me tell you, I was very impressed. If you have a significant other who cannot drive stick (and I know women who can drive stick but their male SOs cannot), the WRX with a CVT is a good alternative in my opinion. My first impression? Wow, this engine is good.

My reference points are my old 2005 Evo 8 and my bro-in-law’s 2002 WRX wagon. The Evo 8 4G63 was rated at 271hp and the 2015 WRX is rated at 268hp, so basically the same. And the old EJ20 was around 227hp. Everyone who remembers the old EJ20 remembers it was a dog below 3000rpms. My Evo 8 was good once you got to 2500rpms and you could lug it down at around 2000rpms. With the new FA20DIT, it starts moving well at 2000rpm and you can lug it down at around 1600rpm. The response of the FA20DIT is also superior to old 4G63 and EJ20. Keep in mind the 4G63 was also a twin-scroll turbo, but the direct injection of the FA20DIT allows for wonderful things in terms of performance. To be fair, you would hope a decade of time would make for a better engine. Overall, I would compare the engine to the VW/Audi 2.0L gas turbo engine like in the VW Golf. The torque comes on early and hard with good response.

That decade of improvement has also benefited the fuel economy. On a pure highway cruise, I was able to eek out 26mpg from my Evo. I was able to do 29mpg pretty easily in the WRX. Of note, only use premium. Whoever had the car before me must have put in regular 87 octane as I was only getting 26mpg on the highway. As soon as I filled the car up with piss-water Cali 91 octane, the fuel economy jumped to 29mpg. I bet with some good 93 octane, the fuel economy can be even better.

 

If you baby it a bit, you can get better than EPA rated mpg; the WRX is rated at 28mpg hwy. I was able to average this 30.3mpg over a 140miles highway stretch which did include some infamous LA Interstate 405 traffic. The line in the graph is a moving average and the bars show where I was above and below the average. You can see how my mpg dropped at the end of the drive once I hit city streets.
Should you need some more torque and power, simply hook up the COBB AccessPort.

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