- Boxer engines.
One of the most iconic automotive sounds out there
(car engine rumbling) is the rumble
of that Flat 4 EJ powering all four wheels
of the Subaru WRX STI.
It's been the heart of the STI for 26 years
and now
Subaru has thrown it out.
And they're putting in an engine from an SUV.
That burdens your bridges, chaps your burn,
tans your hide.
It just plain ticks you off.
Oh, I have good news for you.
This engine is the best engine the STI has ever had.
And today I'm gonna show you exactly why.
We're gonna look at this new FA24 engine
and find out where it's hiding all
that buff Boxer potential.
Don't believe Subaru can turn a mom mobile motor
into a Flat 4 phenom? Well, I guess we just got to show you.
Let's go
(dramatic upbeat music)
(buzz)
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(beep) Now if you don't know,
the rumors are all but confirmed
that the new Subaru WRX STI is coming in 2022
with the revised version of the FA24 engine,
currently in the Subaru Ascent.
And supposedly the STI will make a total 400 horsepower
to the wheels.
Now to put that in quick perspective,
that's 90 more than the current STI,
60 more than the most powerful STI
and 140 more than what the Ascent makes right now.
Now, quick note before we get too deep,
we're going to be saying FA and EJ a lot today.
Now, if you don't know what those mean,
it's simply the engine code that Subaru uses
to identify their Boxer power plans.
EJs were the two-liter and two and a half liter engines
that came in the WRX and the STI
all the way from the beginning
and the FA engines are the new platform.
These engines don't have the same "Suby rumble",
but it's theoretically got more power.
So where is that extra power coming from?
Well, let's take a look.
(upbeat music)
One of the main things that's new for the FA engines
is direct fuel injection,
as opposed to the EJs' port injection.
Now port injection is when your fuel injector
is placed in the intake manifold
upstream of the intake valve
and the air and fuel mix there
before they enter the cylinder.
Now, the upside of that, is that the air and fuel
have a longer time to mix before they enter
into the cylinder.
But the downside is that it's less precise
on the air:fuel ratio
because you're losing a little bit of fuel
as it sticks to the intake valve.
Now direct injection means that fuel is shot directly
into the cylinder. It's injected directly,
just like the spark is.
And the fuel was fired much later and much more precisely
than port injection and it's fired
at a much higher pressure.
And there are plenty of benefits from this.
Now the system is more efficient,
meaning better fuel economy. That's good.
And also it cools the cylinder
because it sprays a nice mist of fuel on the cylinder walls.
And that lowers the temperature of the wall.
Reducing the chance of pre-ignition or engine knock
that might occur from the combustion chambers heat.
Think about that heat, the cylinders get so hot
that they can sometimes when you inject fuel in
cause it to auto ignite, it's not good.
It creates knock, ping.
You don't want it.
You don't want it. (beep)
Ultimately direct injection is better for fuel efficiency
and engine health,
which overall let's the engine safely hold more power.
But there are some downsides to it.
There's always good and bad.
Direct injection needs the engine to be warm,
to atomize fast enough and mix with the air
and overcome that they need a lot more fuel on a cold start.
Trust me, direct injection is the way to go,
but if you're not sold on it,
then I got some good news for you. Okay.
If you will please indulge me
and take a quick trip over to
the speculation zone. (soft sci-fi music)
In the current Subaru BRZ,
also the Toyota GT86.
Toyota's fancy D4-S fuel system uses both port
and direct injection.
And it's actually a very simple system.
The direct injectors are strong enough
to run the engine at high RPM,
but for better startup,
the engine splits the work between the two sets of injectors
at cold start.
Literally the best of both worlds.
And this version of the D4-S system,
isn't in the FA24 engine currently,
but it could be added assuming the STI
isn't going to use the same intake manifold.
Now our buddies over at Prime Motoring in New Jersey
have been tuning Subarus for years
and they took a closer look at the existing FA24.
And they had been tinkering with it
just to see what the new STI is going to be capable of.
And with a new intake manifold,
the FA24 could totally use this D4-S system from the BRZ.
But that's not the only promising thing
they found in the new engine.
The block and head themselves has some hidden heft as well.
(upbeat music)
Even though it's still a Flat 4
and it's got about the same displacement
as the old EJ257, the FA24 is 100% new engine.
And Subaru has had a lot of time
to improve on how they make power.
The cylinder head on this new engine
has more of a straight shaft for airflow
than the EJ had with its more dog-leg path
for the air to go through.
You know what a dog leg is. It looks like this.
It looks like a Ben Cheeto.
You may not think that these little angles
could slow down free flowing air,
but in an engine and especially in a turbocharged engine,
a free flowing path is super duper important.
Now, if the pathway is causing air to bounce around
creating turbulence and pressure pockets,
the air can only go so fast.
And at high revs,
it can't get air into the cylinder fast enough.
So we always want a freer flowing head, to get us more air
because we know our famous equation,
more air plus more fuel equals more power.
Now we've already got more fuel from the direct injection
and now we've got more air.
But for every engine, there's a breaking point.
A point where if you put too much air in,
and you put too much fuel in,
you're gonna get too much combustion
for the block to handle.
And the main thing about an engine's block
is that it's got to be strong.
Those cylinder walls have to be thick enough
to withstand the pressure that the engine is gonna make
or else,
Well, there's no easy way to say this.
Your engine will blow up.
Let's say with a turbocharged engine,
you're making 15 pounds of boost or 15 PSI of pressure.
That's pressurized air that goes into this cylinder
on the intake shaft.
And when the piston is fully down
that's the most space available,
and then the intake valve closes
and that air goes all the way back up
and it gets compressed
as the piston gets pushed back up again.
And an engine let's say with a 10:1 compression ratio,
you're looking at roughly 150 PSI.
That is a lot of pressure,
but that's not a lot of pressure
compared to what happens next.
The spark.
Once that spark hits that compressed air and fuel mixture,
it ignites, it creates a combustion.
And that pressure jumps to anywhere between
300 and 1000 PSI, forcing that piston all the way back down.
So the cylinder walls have to withstand that pressure,
right at the moment of combustion,
getting forced all the way down all the way up
and that's happening thousands and thousands of times
a minute.
So how does the FA24 handle that?
Well, it's got thick (beep) cylinder wall.
And not only does it have thicker cylinder walls
than it's EJ bro bro, it's got more cylinder support
molded into the casting.
And in an engine that can take more pressure.
You can up the boost or up the compression
to make more power,
but cylinder walls aren't the only thing
that needs to be beefy to make power in an engine.
And lucky for us Suby-loving Boxer boys,
the FA24,
just like Arby's sandwiches.
It's got more beef inside.
Has more beef- Okay stop it.
(upbeat music)
The FA engine has been around a little while
and it's gotten its fair share of complaints,
but in a way, that was kind of the point.
Subaru used the FA20 DIT as a test bed
for what the FA24 would eventually become.
And inside their SUV engine
are some really over engineered parts.
It's almost as if they were designing this engine
with something else in mind.
Now the connecting rods were a point of failure on the FA20.
All that pressure that we talked about earlier,
pushing down on the piston.
Well, it also pushes on the connecting rods,
which connect the pistons to the crankshaft.
Now this is where the direction of our energy changes
from the pushing force of the combustion
to the rotational force.
Now that connecting rod is attached to the crankshaft
off center
and it's attached to the piston on a pivoting pin.
So as it gets pushed down, it rotates the crankshaft,
thereby rotating your flywheel
and eventually rotating your wheels.
Linear motion to rotational motion.
That's all an engine does.
Can you do this?
Can you guys do this?
I think that's like- Yeah. That's like,
(chuckles) (beep)
And this thing is tough,
because that energy has to change direction.
And that puts a lot of stress on the connecting rods.
The more pressure there is,
the more likely you're going to bend or break a rod.
Now it's not enough
to just say the new engine has stronger rods.
So we'll show you instead.
Now the new FA24 rods are almost twice as thick
as the old FA20 ones.
These things are going to be able to handle
a lot more combustion pressure,
but the rods aren't the only thing that had an upgrade.
FA24 has gone to the new beehive valve springs.
buzz buzz buzz.
A beehive refers to the shape of those springs.
Normal springs look like this.
They're shaped like a normal spring.
Now beehive springs are smaller at the top
and bigger at the bottom.
Kind of like a beehive or maybe
like one of those honey dripping tools that people use.
You know, you dip it in honey. I actually have one.
You want me to go get it?
I can show them.
(chuckles)
So what I do know is that these valve springs
make a big difference.
They're designed to increase effective spring rate
and combat valve flow.
And as your engine revs higher and higher,
the camshaft spins faster and faster.
And the cams push those valves open
and the valve springs are what push the valve closed
back again.
But what if your cam is being so fast
that it pushes the valve open again
before the spring can fully close it?
Well, this is called valve float.
And to fix it, you need stronger valve springs.
and you can go with thicker springs.
You can double or triple the strength of those Springs,
but that adds a lot of wear to your valve train.
Now beehive springs have a progressive spring rate
and overall require less force
to move them at the same speed as normal springs.
So the upshot of this
is that you get less wear on your valve train.
That's great.
And your springs can also handle revs about 500 to 700 RPM
higher than they could with a traditional spring.
So thanks beehive spring.
So all this new stuff is in theory,
gonna make the new STI a better platform
than the old EJ one.
And even though Subaru,
hasn't pushed the EJ beyond 340 horsepower.
I'm sure some of you are gonna point out
that tuners have been able to push it
way beyond 400 horsepower.
In fact, we showed you an 800 horsepower one
on this very show.
Now most tuners will say, to get 400 horsepower reliably,
it takes forged pistons,
forged rods,
new bearings,
new machining,
a bunch of new parts, right?
I mean, basically you're taking the whole engine apart
and replacing half of it.
For the new FA24 to get that same 400 horsepower.
It looks like it might take a lot less.
Prime Motoring has been putting these engines to the test.
Here's their engine mounted in a Crosstrek
making 500 horsepower to the wheels
with nothing but bolt-ons and attune
and even the Turbo and Cams and ECU,
or just the OEM ones from a WRX.
And they've run it on the dyno over 50 times.
Look, EJ engines are sick.
And if you want to know more information about them,
go watch this episode of Up to Speed.
James is going to gush all over them.
It's really great episode, but let me tell you,
the FA is the wave of the future
and it's going to provide us
with some super high horsepower reliable WRXs.
And man, there's nothing more we can ask for.