Next Subaru WRX STI Aims to Top 400 Horsepower

Subaru plans on delivering the goods in 2021 when it debuts the next incarnation of its flagship performance model. Rather than incrementally improving the WRX line as it has in the past, Subie looks to be kicking down the stable doors to drag as many horses as possible back to the factory for canning beneath the WRX STI’s hood.

A recent report from Forbes claims Subaru’s engineering team has targeted a minimum of 400 horsepower and 361 lb-ft of torque for the next STI. While the outlet initially referenced the motor as entirely new, it later clarified that it was technically the same 2.4-liter FA24 that currently powers the brand’s Ascent crossover — and was already assumed be adapted for use on the next WRX among those paying close attention. However, it’ll have to undergo quite a bit of work to deliver the figures being claimed.

In the Ascent, the turbocharged boxer produces 260 hp and 277 lb-ft; fine for taking the kids to school, but perhaps lackluster to those more concerned with quarter mile times or blazing up a mountain trail faster than anyone else. Subaru will undoubtedly have to engage in aggressive tuning and adopt stronger engine components to get there.

From Forbes:

In next-generation WRX STI spec however, that same FA24 engine will receive significant upgrades to achieve that smoking hot figure of 400 hp. According to our source, the reworked FA24 in STI spec will employ a reinforced crankshaft and pistons, optimized timing balance, fine-tuned valves and intake ports, boost pressure will be tweaked and brake capacity will be enhanced, among other modifications. And married to the brand’s tried and proven symmetrical full-time 4WD system, expect nothing less than class-leading performance and handling.

In creating the new more powerful STI engine, Subaru engineer’s apparently benchmarked the Mercedes-AMG 2.0-liter turbo — as found in the A45 and CLA45 — which pumps out 416 hp and 369 lb-ft of torque. This engine is currently recognized as the most powerful 2.0-liter series-production four-cylinder engine on the planet.

The big question for yours truly is what this means for the regular WRX. The FA24 has already migrated into other models, so it’d be surprising not to see it in the more street friendly model. Earlier rumors suggested the STI would have the mill running somewhere near 315 hp (barely more than it makes now). Those figures may have been intended for the WRX if the reporting from Forbes is true.

True to form, Subaru has been impressively cagey about any details relating to either car. We can’t really do more than speculate. Still, there’s been enough amped-up FA24 news for us to feel confident about it debuting in the STI in 2021… and lots of conflicting information before that. In 2017, UK marketing director Chris Hawken indicated a hybrid powerplant was under consideration for both WRX models; previous quotes from Subaru indicated the motor was developed to prioritize torque and efficiency over horsepower. While heaps of torque seems equally agreeable, early indications had us believing this wasn’t the unit the company had in mind for its most exciting models.

Regardless, the Japanese-spec EJ20 will be able to retire with the American-spec EJ25 remaining in service until Subaru is ready (presumably very late 2021 or early 2022). Visually, all future WRX models are supposed to take their cues from the various Viziv concepts revealed over the past few years. That procession began at the 2017 Tokyo Motor Show. Lately, we’ve seen more realistic versions earn their time in the spotlight. Considering the model’s design history, it might never have mattered what it looked like. WRX drivers aren’t known for being bastions of good taste or caring about what others think. They’re typically much more interested in math, specifically as it relates to their own car.

We imagine they’ll be pleased if Subaru starts throwing out big numbers, even if the car itself isn’t a looker.

[Images: Everyonephoto Studio/Shutterstock; Subaru]