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Old 02-17-2018, 10:15 AM   #1
bugatti0628
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Default The FA24 DIT in depth

https://www.google.com/amp/amp.timeinc.net/thedrive/news/18562/meet-subarus-new-fa24-boxer-engine%3fsource=dam
The engine in the ascent is capable of alot more than it is currently putting out. How does that apply to other products the engine may go into.
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Old 02-17-2018, 11:27 AM   #2
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I am really excited for this engine. I absolutely love what they did with the FA20DIT. Almost 3 years of daily abuse and this thing is just asking for more. Overall, I am really impressed with it and I don't even like 4 cylinder turbos.
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Old 02-17-2018, 11:41 AM   #3
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This goes into a new wrx model and I’ll be first in line
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Old 02-17-2018, 12:17 PM   #4
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If it was designed with torque/towing in mind, I'm going to assume Subaru beefed up the connecting rods. I must admit that my stage 2 Fa20DIT has taken 3 years and 50+k miles of abuse and still runs great.

I'd wager to say that Subaru will most likely keep the FA20DIT in the WRX and use a variant of the FA24DIT in the STi
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Old 02-17-2018, 01:30 PM   #5
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Originally Posted by 2015Sapper View Post
If it was designed with torque/towing in mind, I'm going to assume Subaru beefed up the connecting rods. I must admit that my stage 2 Fa20DIT has taken 3 years and 50+k miles of abuse and still runs great.

I'd wager to say that Subaru will most likely keep the FA20DIT in the WRX and use a variant of the FA24DIT in the STi
Good to hear. The FA motors are phenomenal until you start to get silly with the mods. If you take a step back and really think about it, a "stage 2" WRX is pushing crazy amounts of HP/L and is an absolute blast to drive.
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Old 02-17-2018, 02:45 PM   #6
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Was there more to that article than just one page? It was quite shallow for an in-depth review if not.
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Old 02-17-2018, 04:11 PM   #7
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There is literally nothing "in-depth" about this article. Anyone here could have concocted that.
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Old 02-17-2018, 06:30 PM   #8
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This motor “article” generates lots of clickbait at low RPMs.
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Old 02-20-2018, 03:01 AM   #9
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I like my FA20DIT. I have it protuned to 285hp/325ftlbs torque to the wheels (tuned when it was very cold out). These engines are super torquey. I'm afraid to go any higher than that before the rods fold but if the 2.4 goes into the sti with stronger rods I'll definitely upgrade to that.
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Old 02-20-2018, 09:46 AM   #10
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Quote:
Originally Posted by RealDealTarheel View Post
Was there more to that article than just one page? It was quite shallow for an in-depth review if not.
Maybe the bore/stroke was published somewhere else, but we for sure know it's an over square engine... and Subaru said this over square engine was built for torque.
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Old 02-20-2018, 10:15 AM   #11
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Maybe the bore/stroke was published somewhere else, but we for sure know it's an over square engine... and Subaru said this over square engine was built for torque.
we know there will be a increase in power, but then there is the torque for the sti also. The power to accelerate and move the vehicle. The other big thing is fuel efficiency. The ascent weighs more than the STI, yet it get better fuel efficiency than the STI. Now the ascent has an automatic. But what does this mean for the possibility of an auto sti. More power and torque with the added benefit of more fuel efficiency and the addition of eyesight for the first time on an STI in the US.
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Old 02-20-2018, 10:24 AM   #12
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An over-square design makes it hard to safely make torque with today's emission requirements. It seems like the 2.4T has the same potential if not more with the 87 tune to break ring lands as the 2.5T.

The frame rails are just killing Subaru engine design.

Peace,

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Old 02-20-2018, 10:30 AM   #13
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Quote:
Originally Posted by bugatti0628 View Post
The ascent weighs more than the STI, yet it get better fuel efficiency than the STI. Now the ascent has an automatic. .
That has as much to do with the FA24 being direct injected as it does the Ascent being an auto.

The mpg's on my wife's '15 WRX are fantastic. I'm no EJ hater by any stretch, but I have become a big fan of the FA DIT engines in the 3 1/2 years of ownership.

Last edited by Shik; 02-20-2018 at 01:43 PM.
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Old 02-20-2018, 12:23 PM   #14
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That has as much to do with the FA24 being direct injected as it does the Ascent being an auto.

The mpg's on my wife's '15 WRX are fantastic. I'm no EJ hater by any stretch, but I am a fan of the FA DIT engines in the 3 1/2 years of ownership.
true, true
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Old 02-20-2018, 12:48 PM   #15
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The FA24 in the ascent is tuned specifically for more torque and towing capacity, while also yielding good fuel economy despite the ascents size and weight. What adjustments will they make for the lighter outback and legacy. If this engine is going in the STI, it will be even lighter than the ascent, legacy, and outback, and the transmission and engine will be tuned accordingly.
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Old 02-20-2018, 01:29 PM   #16
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Quote:
Originally Posted by b4wantab View Post
The frame rails are just killing Subaru engine design.
Actually, it's the engine crossmember. If Subaru went to a shallow V, like, 170degrees or so, they could A) further lower the engine in the engine bay and B) if in this hypothetical engine the crank is lowered in the chassis in comparison to where the heads currently reside, there is your extra stroke.
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Old 02-20-2018, 01:51 PM   #17
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Quote:
Originally Posted by b4wantab View Post
An over-square design makes it hard to safely make torque with today's emission requirements. It seems like the 2.4T has the same potential if not more with the 87 tune to break ring lands as the 2.5T.

The frame rails are just killing Subaru engine design.

Peace,

Greg
My point was that an over square engine is inherently not designed for torque. Over square engines are built for power. Maybe it was a translation issue and the subaru engineer meant that the engine management was tuned for torque.

Bottom line, you want torque, you make longer stroke, not bigger bore.

but hey, new engine design allows for all sorts of cool things like better combustion chamber designed for newer emissions standards that can overcome packaging restrictions.

so don't despair, and don't start rumors about ringlands in a brand new engine that you can't back up.
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Old 02-20-2018, 03:14 PM   #18
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Quote:
Originally Posted by bugatti0628 View Post
The FA24 in the ascent is tuned specifically for more torque and towing capacity, while also yielding good fuel economy despite the ascents size and weight. What adjustments will they make for the lighter outback and legacy. If this engine is going in the STI, it will be even lighter than the ascent, legacy, and outback, and the transmission and engine will be tuned accordingly.


Why would they put the FA24 in the outback, legacy etc? Wouldn’t those get the DI version of the FB?
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Old 02-20-2018, 03:19 PM   #19
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Quote:
Originally Posted by samagon View Post
My point was that an over square engine is inherently not designed for torque. Over square engines are built for power.
While I know what you meant (high RPM power vs. low RPM power), I can't stand stating it like this.

At any given RPM, more torque means more power. A long stroke engine has the potential to make more lower end power, but present an RPM limit (thus limiting top-end power), as the piston speeds are so great given the long stroke.

That being said, in a turbocharged car, it's not like they were going to give us a big enough turbo to flow well enough at 7k+.

Why do we call power at low RPMs torque? And torque at high RPMs power?
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Old 02-20-2018, 05:08 PM   #20
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so don't despair, and don't start rumors about ringlands in a brand new engine that you can't back up.
Not starting rumors, just stating that on paper it has it's work cut out for it. Without the scavenging effect of the higher air velocities associated with longer stroke to bore ratios, tuning for EPA is rough. Correct? What am I missing?

Now take that whole problem, use some existing parts that fit a limiting package and run lower octane. Just sounds like too many compromises.

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Old 02-20-2018, 05:36 PM   #21
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Quote:
Originally Posted by SoapBox View Post
While I know what you meant (high RPM power vs. low RPM power), I can't stand stating it like this.

At any given RPM, more torque means more power. A long stroke engine has the potential to make more lower end power, but present an RPM limit (thus limiting top-end power), as the piston speeds are so great given the long stroke.

That being said, in a turbocharged car, it's not like they were going to give us a big enough turbo to flow well enough at 7k+.

Why do we call power at low RPMs torque? And torque at high RPMs power?
I should have said horsepower

sorry, it was what I meant.

Quote:
Originally Posted by b4wantab View Post
Not starting rumors, just stating that on paper it has it's work cut out for it. Without the scavenging effect of the higher air velocities associated with longer stroke to bore ratios, tuning for EPA is rough. Correct? What am I missing?

Now take that whole problem, use some existing parts that fit a limiting package and run lower octane. Just sounds like too many compromises.

Peace,

Greg
I suspect the EJ was limited in how they could design the combustion chamber to the shape of the dome of the piston.

I suspect the FA24 allows for not just combustion chamber shape changes on the head as well as piston dome, but also intake and exhaust port changes that make that better too.

while yeah, you're fighting physics, you can still make things more efficient with an updated design that takes current regulations into consideration (rather than building on tech that was originally designed back when carbs were still installed at the factory).

Last edited by samagon; 02-20-2018 at 05:45 PM.
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Old 02-20-2018, 08:19 PM   #22
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Why would they put the FA24 in the outback, legacy etc? Wouldn’t those get the DI version of the FB?
for the base engine maybe, but not for the flat 6 replacement.
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Old 02-21-2018, 09:02 AM   #23
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while yeah, you're fighting physics, you can still make things more efficient with an updated design that takes current regulations into consideration (rather than building on tech that was originally designed back when carbs were still installed at the factory).
Agree. But again there comes that comment about fighting physics. It is the same thing with the CVT. First comment is "why would they do that, you are fighting physics?" Yes, engineers can make anything work but what are the compromises? FHI/Subaru for the last few years seems to be making choices that are already long shots. Why? Use all that engineering prowess to improve good bets not just make long shots work.

Peace,

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Old 02-21-2018, 10:03 AM   #24
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Subaru has been involved with CVT for 30 years now. Chew on that.
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Old 02-21-2018, 12:17 PM   #25
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Subaru has been involved with CVT for 30 years now. Chew on that.
Already spit it out.

Peace,

Greg
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