The tuning capability of the Ascent’s 2.4-liter engine could open a lot of doors

We’ve learned a lot about the next-gen Subaru BRZ and Toyota 86. We know that a deal between both companies will make Subaru an affiliate company of Toyota and that the twins will switch over to Toyota’s TNGA platform. More recently, we learned that they would both feature a turbocharged version of the Subaru Ascent’s 2.4-liter flat-four,, and that’s a bigger deal than we thought. A new report says that the 2022 Subaru WRX STI will feature the same exact engine, although it will be tuned to deliver 400 horsepower. Does that mean that, with a little extra work, the Subaru BRZ and Toyota 86 can be pumped up to that level of performance too?

When Will the New Subaru WRX STI Launch?

2020 Subaru WRX Exclusive Renderings Computer Renderings and Photoshop Exclusive Photos
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Forbes’ secret sources say that the current WRX will continue to be powered by the EJ25, 2.5-liter Boxer four until the next-generation model is introduced sometime after 2021. That means that, at the very earliest, the WRX could launch as a 2022 model.

Why Will the Legendary Subaru EJ25 Be Discontinued?

2018 Subaru WRX STI High Resolution Drivetrain AutoShow
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The current EJ25 engine is good for some 305 horsepower in the standard WRX and has been tuned to as much as 341 horsepower and 315 pound-feet of torque in the most recent 2020 WRX STI S209. Those are admirable numbers, but the strict and ever-changing emissions regulations require some change, and the EJ25 just doesn’t hold up anymore.

Since the FA24, 2.4-liter from the Ascent is cleaner and more emissions friendly, it is, reportedly, the engine of choice for the next-gen WRX.

That changeover comes with some major benefits outside of the improved emissions output, and that’s tunability. According to Forbes, the FA24 will be capable of producing as much as 400 horsepower. Let’s just take a minute to thank the universe that it’s happening in the WRX and not a hotter version of the Ascent, am I right?

2020 Subaru WRX STI specifications
Engine 2.5-liter flat four-cylinder “boxer”
Horsepower 305 HP @ 6,000 RPM
Torque 290 LB-FT @ 4,000 RPM
0 to 60 mph 4.6 seconds
Top Speed 160 mph
Transmission 6-speed manual
Fuel economy city/highway 17/23
Curb weight 3,391 Lbs

How Will Subaru Tune the Ascent’s Engine to 400 horsepower?

2019 Subaru Ascent
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Tuning the Ascent’s FA24’s 2.4-liter engine to 400 horsepower for the WRX STI isn’t going to be all that easy. Sources indicate that Subaru is going to completely rework the engine by making a number of enhancements:

  • New, reinforced crankshaft
  • New, reinforced pistons
  • Optimized timing balance (valvetrain to crank)
  • Fine-tuned valves
  • Revised intake ports
  • Tweaked boost pressure (most likely increased somewhat significantly)
  • Improved, high-pressure fuel system
Subaru Viziv Performance Concept
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2017 Subaru Viziv Performance Concept

On top of this, Subaru will also up the WRX STI’s brake capacity to compensate for the huge improvement in power. After all, we’re talking about an improvement of 95 horsepower over the current STI. The Symmetrical AWD system will naturally carry over, also likely returned, and there will be a whole host of other chassis modifications, too.

Will the Engine in the Subaru BRZ and Toyota 86 Be that Same as in the Next-Gen WRX STI?

2017 Toyota 86 High Resolution Exterior AutoShow
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This is the big question that has yet to be answered. We know that the Subaru BRZ and Toyota 86 will employ the same engine in some respect, but most recent reports indicate that their turbocharged output will only be bumped up to 255 horsepower and 200 pound-feet of torque. However, Toyota has been adamant that the next-gen 86 will surpass the Supra in terms of driving dynamics – it’s meant to be a true driver’s car, of course – but whether or not that long list of updates taking place to make the FA24 WRX STI worthy is a mystery.

Considering the fact that Subaru will have to produce both engines, it’s highly possible that at least some of the internals, like the reinforced crankshaft and pistons, for example, could be found inside the FA24 that will power the BRZ and 86 twins.

However, the revised valvetrain and intake, as well as boost tuning and timing balance, probably won’t be present when it rolls off the production line. But that’s not necessarily a bad thing. If Subaru has laid the groundwork with the pistons and crankshaft, the other modifications needed to push the BRZ or 86 into high-300-pony territory won’t be that huge.

2017 Subaru BRZ High Resolution Exterior
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In the world of tuning, swapping out an intake manifold and cylinder head isn’t that difficult and, if they feature the same turbo, tuning the boost and fuel delivery could be as simple as modifying the ECU. So, while it won’t be impressively easy to reach the same output as the WRX STI, one could come close without doing a lot of major work. A bump up to, say 320 horsepower, could potentially be done by simply swapping out the turbo and doing some computer calibration. It might not be something you can do in your backyard, but you can bet aftermarket tuners will be all over it – especially if the lower-end of the engine is already primed to handle that much power.

Final Thoughts

Subaru Viziv Performance Concept Exterior
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Right now, how the FA24 engine will differ between the BRZ\86 and the WRX STI is a big mystery, but Subaru would have to go out of its way to produce the same engine with different internals (crank and pistons,) so the reinforced lower end is actually a strong possibility. I wouldn’t hold out much hope for the improved heads or intake, though. The point is that the next-gen BRZ and 86 could be very tunable if things work out right, and that’s a pretty big deal in our book.

Source: Forbes

Robert Moore
Editor-in-Chief and Automotive Expert - robert@topsped.com
Robert has been an auto enthusiast his entire life. He started working cars at a young age, learning the basics from his father in the home garage on the weekends. As time went on, Robert became more and more interested in cars and convinced his father to teach him how to drive when he was just 13 years old. Robert continued working on cars in his free time and learned as much as he could about engines, transmissions, and car electrical systems, something that only fed his curiosity more and eventually led him to earn a bachelors degree in automotive technology with a primary focus on engine performance and transmission rebuilding.  Read More
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