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If you want Subaru’s best engine they’ve ever designed, you can get it in the 2020 Outback, Ascent, and Legacy models. Subaru put the new smaller 2.4-liter turbocharged engine in the Ascent family hauler first, the biggest vehicle they’ve ever made. It was a good move because the new FA24 (which is the engine code that Subaru uses to identify its Boxer engines) has what you want, more power and improved fuel mileage.
When Subaru discontinued the 3.6-liter in the Outback, they needed an engine that would bring power, fuel efficiency, and be reliable for customers. Subaru engineers succeeded in a big way and it’s why it will be the brand’s engine of the future. We want to give a shout out to Donut Media, where the technical information for this article came from.
Customers want an engine that's going to be reliable and not be in the shop for repairs. How did the Japanese automaker squeeze so much power out of the smaller engine without blowing it up?
One of the biggest improvements in the new FA24 2.4-liter turbocharged powerplant is the addition of direct fuel injection as opposed to the older version port injection in the 3.6R. Port injection places the fuel injector in the intake manifold upstream from the intake valve. The air and fuel mix together before entering the combustion chamber and it’s less efficient.
Direct injection shoots the fuel directly into the cylinder delivering a much more precise air/fuel mixture and improves efficiency. It increases the pressure and thus horsepower, and also lowers the temperature in the cylinder, lowering the chance of pre-ignition.
Subaru also improved the cylinder head giving the air a straighter shot into the cylinder by taking out the bends. This takes out turbulence and improves the air flow at higher revs. More air plus more fuel from the direct injection equals more power.
But Subaru had to beef up the engine block and internals to handle the increase in horsepower. In a turbocharged engine it’s even more critical because of the extra boost from the turbocharger. Subaru increased the thickness of the cylinder walls, and added larger connecting rods, which are twice as thick as the EJ25 turbocharged engine in the WRX STI.
Subaru also needed to upgrade the valve springs. The FA24 comes with new ”Beehive” valve springs that are smaller at the top and wider in the middle, making them stronger and can handle more pressure and higher revs (500-700) than a normal spring.
All the added upgrades in the new FA24 2.4-liter turbocharged engine enabled Subaru to put it in the Ascent 3-Row SUV, the largest vehicle they ever built, and deliver more power and torque than the competitors V6 engines. It’s fuel efficient, and it will be a reliable engine for customers.
The new 2.4-liter turbo four-cylinder Boxer powering the Outback XT, and Ascent produces 260 horsepower and 277 lb-ft of torque and gets an EPA estimated 23/30 city/highway mpg and 26 combined mpg. The Outback Outdoor XT also has a towing capacity of 3500 lbs, up from the previous 2700 lb. limit, and Ascent has a 5,000 lb tow rating. Check out the complete 3.6R six-cylinder vs 2.4-liter turbocharged engine comparison below.
The new FA24 2.4-liter turbocharged engine in the 2020 Subaru Outback, Ascent and Legacy is the Japanese automaker’s best Boxer engine yet and they plan on using it in more models. Look for it in the next-generation 2022 WRX STI and 2021 BRZ sports cars.
You Might Also Like: New Subaru Outback XT 2.4L Turbo Vs. Discontinued 3.6L Engine
Denis Flierl has invested over 30 years in the automotive industry in a consulting role working with every major car brand. He is an accredited member of the Rocky Mountain Automotive Press and the founder of Subaru Report where he covers all of the Japanese automaker's models. More stories can be found on the Torque News Subaru page. Follow Denis on Facebook, Twitter, and Instagram.
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Comments
Time will tell. Turbos
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Time will tell. Turbos boosting an engine that originally could not produce the power puts tremendous strain on the parts regardless how strong you think they are. Boosting has always been stressful for motors. You asking it to do more than it could on its own. Not to mention the lag and problems inherent to the heat and necessary cooling for turbos. Design an engine that can accomplish the need without add tricks and you will have done something.
Perhaps, but I have 2014
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In reply to Time will tell. Turbos by George Burkhardt (not verified)
Perhaps, but I have 2014 Forester with the 2.0 XT turbo. 237000 km só far. 147000 miles No problems at all with this engine and I drive it moderately hard. I never redline it I'll have the carbon cleaned out of the valves and injectors soon but no drop off in performance compared to when new. I change the oil and filter every 6000 miles or so. Maybe I was lucky and got a really good one
This engine was designed from
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In reply to Time will tell. Turbos by George Burkhardt (not verified)
This engine was designed from the ground up for this. Not only that, but the amount of boost they used for this application is relatively small, and then it tapers off at higher rpm. This is all designed to keep the heat down when towing the max capacity of 5000 lbs. I have 0 doubt that this an over engineered engine much like the 2jz of yore. I suspect we won't see any problems with this.
Subaru and others have pretty
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In reply to Time will tell. Turbos by George Burkhardt (not verified)
Subaru and others have pretty much solved turbo reliability and lag issues. Years of competition and production have proven the durability.
There are an awful lot of
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In reply to Time will tell. Turbos by George Burkhardt (not verified)
There are an awful lot of Diesel engines that would tend to disprove your contention. And EccoBoosted Ford F150s, too.
I wouldn't dare compare this
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In reply to There are an awful lot of by Steve (not verified)
I wouldn't dare compare this engine with the ford ecoboost engine. I had a 2.3 mazdaspeed 3 w/ that POS ford engine and can tell you that this is a different animal. I agree that only time will tell, but My Outback wilderness is incredibly strong and fast at 15K miles whereas I had to have the smoking turbo in the MS3 replaced by 17K miles. I did buy an extended warranty just in case, but so far it's been reliable.
Well, it seems you aren't up
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In reply to Time will tell. Turbos by George Burkhardt (not verified)
Well, it seems you aren't up to date on new technology if you believe those statements to be true. Twin scroll turbos for one, aren't like the old ones you undoubtedly refer to, and the lag is minimal. That's just one idea you have that's out dated and inacurate. Get with the times and modern day technology and get off the 1982 LS swap mentality and realize Subaru and the turbos are where it's at nowadays b
History proves turbo-…
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In reply to Well, it seems you aren't up by Chad Thomas En… (not verified)
History proves turbo- charged engines do not last nearly as long, and physics support that fact! That's one!
2- Surely you are not suggesting we should reasonably compare diesel engines to gasoline powered engines!
3- Even Subaru's own stats claim an improvement in fuel mileage! 30 mpg highway, I have a 2012 Outback which gets better than that! How is it that 30 is better than 32+mpg?
You could be right - they
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In reply to Time will tell. Turbos by George Burkhardt (not verified)
You could be right - they developed mobile one turbo oil for armored personnel carriers - there's really nothing like Detroit engines to win the war like we did - even though my son intercepted terrorist communique in the battlefield - they had three Neutron bombs and we're fixing to detonate them between NATO and Russia During Reforger1 point taken you need a good platform with honest engines not trickery under the hood - amen to the higher power in America - may God bless everyone worthy of their blessing- colonel Abraham McKenzie
I strongly disagree with this
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I strongly disagree with this analysis. The new turbo is noisy and the drive characteristics are not smooth compared to the 3.6R drivability. The lack of no engine stop feature makes city driving awful. Our mileage calculations after using a week long loaner Did Not offer superior fuel mileage. Both my wife and sons prefer our 2019 3.6R. Our 2019 is the third 3.6 we’ve owned. Discontinuing the 3.6 is a great loss to the Subaru engine choices
We just bought my wife an
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In reply to I strongly disagree with this by Tom Mitchell (not verified)
We just bought my wife an Outback LTD XT with the turbocharged 4-cylinder boxster engine. We both find this vehicle to be powerful, fun to drive, and quiet. On the 1st tank we averaged 25 mpg in basically city driving. Time will tell on how reliable this engine will be, but thus far I think I have more trust in the Subaru engineers than in the naysayers..
The Outback does have auto
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In reply to I strongly disagree with this by Tom Mitchell (not verified)
The Outback does have auto start stop, only the Ascent doesn't have it. I'm sure it's coming though.
Your mileage may very but of course the Ascent got worse gas mileage than your 3.6 outback, it's a bigger vehicle. I've tried to hyper mile a 3.6 outback and best you can get is 30/31. I could easy get that out of the Ascent. I haven't tried on the new Outback xt yet, but I'm sure I'll get to.
Also the 3.6r was notoriously neck snapping on throttle uptake, another problem that doesn't exist with the new engines. I will say in certain cases the 3.6r did shine, I do feel it was a little quieter than the 2.4t especially under throttle. But honestly, the 2.4t sounds good and definitely reminds you that it's definitely a boxer under the hood. Not only that but testing shows it puts out only 12 pounds of boost, with very little lag, I imagine it's a small twin scroll. Which also speaks to its planned longevity.
I could not agree more. Went
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In reply to I strongly disagree with this by Tom Mitchell (not verified)
I could not agree more. Went from a new 3.6 Outback to a 2021 Ascent for tall son-in-laws and new grand children. Need the seating and room. Love everything the Limited edition came with except the woefully inadequate turbo 2.4. Noisy and choppy acceleration. Does not seem to communicate with the transmission either. My daughter’s all have Subaru’s and love them. All SUV ratings have the Ascent at 7-8th place . Don’t know if Subaru engineers notice? The Dealership says this just characteristic behavior of the Ascent. I plan on trading to the Kia Telluride soon.
"Lack of engine stop" if your
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In reply to I strongly disagree with this by Tom Mitchell (not verified)
"Lack of engine stop" if your referring to the auto start/stop it exists on everything except the Ascent. And if you were driving an ascent, of course the mileage was worse, it’s 1000 lbs more than an outback.
I don’t really believe the 2.4 is any louder or quieter than the 3.6, if your outside of the vehicle they are both rather noisy, I think they just did a better job insulating the vehicle from engine noise on the 3.6 models. Other than that, they just sound different, boxers are not quiet engines, ask Porsche, they are unique and that’s just part of their character. Unfortunately the 3.6 had to phased out because it didn’t make sense to develop any further due to tightening emissions. A lot of people are upset with the loss, but just as many if not more are excited that Subaru has brought back the turbo 4 to the outback and legacy that haven’t seen that in years, that’s Subarus heritage in turbo boxers.
As far as mileage calculations go, Subarus engines are typically very tight new, and most loaners have less than 6k miles, after the first oil change, it gets better. And usually when people are testing out the turbo 4, they don’t try to get good gas mileage out of it, they try to test performance compared to the 6 cyl. So naturally it didn’t get quite as good gas mileage. The throttle tip in of the 3.6 was something most people hated, few loved, once you got past this the 3.6 was buttery smooth. The 2.4 feels sluggish in comparison, but it’s actually quicker. The biggest change was how the throttle was tuned, its tuned for economy, letting it do its job, and its fine. Trying to get it to drive like the 3.6, impossible. The key is realizing it’s an entirely different animal, leaning the new throttle curve, and knowing what to expect. Having said all that. I loved the 3.6, I love the 2.4t and it seems to be as bulletproof as the best of them. Keep in mind the 2.4 is new, and Subaru will improve it as time goes on. The 3.6 after all was based on the 3.0 before it. It dates back to the 90s. Lots of R&D, the 2.4 is based off the wrx 2.0 turbo, and is a dramatically improved from that. I suspect a lot of your complaints will be addressed in coming years. I suspect on the 2023 models.
these engines were notorious
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In reply to I strongly disagree with this by Tom Mitchell (not verified)
these engines were notorious for oil leaks, and that's why Subaru discontinued them. I'm glad you enjoy yours, and wish you trouble-free motoring. However, I think only time will tell how good these new engines are. So far, so good.
Shure, Porsche proved the
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Shure, Porsche proved the Boxster engine can go 200K, but Subaru needs to update their style, still stuck on that 1970's wagon look.
Got 220k without any engine
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In reply to Shure, Porsche proved the by Brady Ellis (not verified)
Got 220k without any engine work from a 93 turbo .
I think folks may disagree.
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In reply to Shure, Porsche proved the by Brady Ellis (not verified)
I think folks may disagree. The style is still utilitarian as opposed the the avant garde trend in cuvs. What's the point of barely there upset rear quarter windows and useless rear glass. I think the swooped up overdone styling trend is gaudy like a child's rendering of a space car.
Hi, I wish for to subscribe
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In reply to Shure, Porsche proved the by Brady Ellis (not verified)
Hi, I wish for to subscribe for this blog to obtain hottest updates, therefore where can i do it
please assist.
We've owned a 3.6 R Legacy
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We've owned a 3.6 R Legacy which ended up having the engine replaced due to excessive oil consumption, and the new engine started doing the same thing. The 2.4 does not get the consistent mpg's that the 3.6 did but my biggest concern with direct injection is how the intake valves will stay clean since no fuel is able to clean deposits off of the valve especially since the FA 24 does not have a air/oil separator.
As with every Subaru the
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In reply to We've owned a 3.6 R Legacy by Dave Romero (not verified)
As with every Subaru the service will include an upper engine clean which removes all carbon from the intake including the valves. So if you have the proper service performed that won't be an issue.
My 2014 3.6R with a real
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My 2014 3.6R with a real transmission had better power and smoother driving. But the 2020 Outback limited handles and rides way better. Wish I could have both. I also like all the new safety stuff, just got saved from backing into the path of a bicycle that cut behind me in a parking lot.
Isn’t it time Subaru divested
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Isn’t it time Subaru divested themselves of the Boxer engine concept.? It was a flawed concept from the outset and in spite of numerous tweaking and modifications continues to have problems causing grief for the customers and the company.The Ascent is a big vehicle and providing only 260 horsepower is insufficient when others in the industry pride 290 horses and up. Turbo engines are stressed engines trying to squeeze more from less. Subaru get real and provide your customers with a better motor.
I think they are hiring
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In reply to Isn’t it time Subaru divested by Michael T (not verified)
I think they are hiring engineers all the time. Perhaps you can show them how it's done!
Isn’t it time Subaru divested
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Isn’t it time Subaru divested themselves of the Boxer engine concept.? It was a flawed concept from the outset and in spite of numerous tweaking and modifications continues to have problems causing grief for the customers and the company.The Ascent is a big vehicle and providing only 260 horsepower is insufficient when others in the industry pride 290 horses and up. Turbo engines are stressed engines trying to squeeze more from less. Subaru get real and provide your customers with a better motor.
If the boxer engine was a
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In reply to Isn’t it time Subaru divested by Michael T (not verified)
If the boxer engine was a flawed engine design it wouldn’t be in most single and twin engine private aircraft.
But how do you know this ne
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But how do you know this ne engine will be reliable?
How did Subaru handle the problem with intake valve carbon buildup from DI? Are there also Port Injection to wash the valves similar to Toyota DI engines?
How does the author know this
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How does the author know this will be reliable until owners put some miles and years on it? It's not like Subaru hasn't had a steady stream of engine problems. Heck, they set a galactic record for number of years to get a good head gasket. Then their supplier sells them a batch of bad piston rings. Finally their normally aspirated engines seem to have been smoothed out and we get a notice that the transmission in our 2016 Outback gets a warranty extension. I can only guess why.
Horizontally opposed engine
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Horizontally opposed engine configurations are efficient in lower weight distribution, but, inherently not durable for longevity or fuel efficiency. Inline configurations much more durable and I hope to see Subaru change in that regard and more influence from Toyota may contribute. Also agree with comments that a boosted engine requires dedicated reinforcing of critical engine components to withstand the pressures regardless of configuration. Reliability of BMW & Toyota inline engines are legendary to name but a few. Cheers
Re. reliability of BMW and
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In reply to Horizontally opposed engine by pj (not verified)
Re. reliability of BMW and Toyota I couldn’t agree more...
I had a lease of a BMW 530 D biturbo and it was powerful enough. And most reliable for the 3 years of our contract.
The power curve was always going up while pressing the accelerator...until the motor cut off past 7,000 rpms
Only 6 cylinders and 2 turbos...with diesel. What a beast !
Now I drive a Forester 2.5 Limited and is good...but not the same power although I don’t need more with 55/65 mph speed limits...