2020 Subaru Outback
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Is The Subaru Outback And Ascent's New 2.4L Turbo Engine Reliable? Why It's The Best Yet

Customers want an engine that has power, is fuel efficient and is going to be reliable. Did Subaru deliver with the new 2.4-liter turbocharged engine in the 2020 Outback and Ascent?

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.

2020 Subaru Outback

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.

2020 Subaru Outback

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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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 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 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 much solved turbo reliability and lag issues. Years of competition and production have proven the durability.
There are an awful lot of Diesel engines that would tend to disprove your contention. And EccoBoosted Ford F150s, too.
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
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 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 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 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 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.
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 work from a 93 turbo .
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.
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 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 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 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.
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 flawed engine design it wouldn’t be in most single and twin engine private aircraft.
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 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 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
Speaking about the reliability of an engine that launched a year ago is stupid.. We need to wait a few years to know for sure.
@George B. that is certainly not true whatsoever. If you add a turbo to an engine designed without one, then you are adding more stress than the block, pistons, piston rings, etc. we're designed for. But an engine that is designed to have a turbo is completely different. For example, how many Cummins turbo-deisel engine have 1,000,000 miles on them? Diesel designs already put more stress on the components than gasoline designs. But how can they add a turbo and not blow it up? Because the manufacture used parts that are designed to withstand the pressure, that's why.
Wow! Someone with common sense. If an engine is designed to be a turbo engine it has to be beefier out of the gate. I do agree that without data you can not say an engine is great or the bomb diggity of all time. Unfortunately this kind of data is only obtained through actual consumer use. Using a test facility and dyno's are not real world application. Let's hope that Subaru is headed in the right direction.
The greatest contribution to reliability Subaru could make would be to integrate the heads into the cylinder assemblies thus removing the troublesome head gasket at the root of so many problems. This has been done before. The head and cylinder assembly simply bolt onto the crankcase and thus have an unpressurized union to the engine. Cost would not be greater as they have to make a head and cylinder block anyway and then have very comprehensive bolt configuration to ensure a good seal on the current head gasket plus the attachment of the cylinder block to the crankcase.
Good idea but a reliable head gasket on a boxer engine is not rocket science - BMW and Porsche have been doing it for over half a century. Only Subaru's engineers could get it wrong, keep getting it wrong, try a new design and get it wrong again. They could have called BMW's or Porsche's parts department, said send us a head gasket, took it apart to to how it's done, and presto!
Yes, you are correct. They could have just bought a used 911 turbo and taken it apart.
Huh? Subaru's engine was designed to include a turbo charger since before it was designed. They don't need another car or engine to steal parts from. Do you still not understand?