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2020 Forester Sport
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Discussion Starter · #1 ·
I'm picking a 2020 Forester Sport up soon and looking at mod options. I have seen on the upcoming Japanese 1.8L turbo variant that it has dual exhaust and was wondering if there is anything stopping me from doing it to the 2.5L? I know some rear bumper modification will have to happen (or order the Japanese one) for it to fit correctly, is there anything in the undercarriage that will hold me back?

Image of the Japanese 1.8L turbo below.
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2014 2.5i Limited CVT
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With the right amount of money, pretty much anything is possible.

But know that this - generally - is not a true dual exhaust system; rather it's just dual exhaust outlets. All of the exhaust is still going to come from the single mounting point... A true dual exhaust system (on a typical V-shape motor) would have the exhaust header from one side to go to one exhaust pipe (with dedicated cats and mufflers) and the other side to the other.

Most modern vehicles (inlcuding our Foresters) will feed the exhaust (from either 2 manifolds or a single) to just one point and then usually flow back through a single cat, where it's then split to two mufflers and 2 outlets. Like the previous generations - the SH had twin outlets and the SJ generation XT had twin outlets, as well, but were not truly dual exhaust systems.

Even on a single set up (like the new SK and the non-turbo SJ) you should have a split made at some point and then route that 2nd pipe set up out to the other side of the rear. It should be noticed that the SJ still had cutouts for the twin outlets with non-XT models having a trim panel that clipped into place. The SK design has a bumper design that "hints" at the twin outlets, but I don't believe that there is a cut out just covered by a panel like the SJ.

A good bet would be to find an XT and crawl under to see how it's routed and set up. While the SJ and SK are different platforms and have different underpinnings, there is probably enough similarity to at least give you a plan.

One other question - do you want this just for the look or are you expecting some type of improvement in power due to less restrictive exhaust? That latter part wouldn't be probable because you're still limited by the single junction as left side and right side exhaust comes together.
 

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2020 Forester Sport
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Discussion Starter · #6 ·
Thanks for the replies guys, seems like from what your saying it's definitely going to be possible. I'm not really looking for any real power increase just to make the back end more symmetrical.
 

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2021 Forester sport
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30 Posts
57734 SJ320 Rear bumper guard
only getting this from japan. plus you need exhaust heat shield front 15+ STI or XT left side. 59024SG002.

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2021 Forester Limited
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718 Posts
Looks Good! IIRC, there is a pop out panel on the SK rear fascia. I noticed it when installing my rear hitch.

One other question - do you want this just for the look or are you expecting some type of improvement in power due to less restrictive exhaust? That latter part wouldn't be probable because you're still limited by the single junction as left side and right side exhaust comes together.
The reality is as far as exhaust fow, it will be slightly harder for the engine to push the gasses out of a dual exit set up. (Assuming the split is the same diameter as the pipe feeding it)

The added volume of the split will slow the velocity of the gasses in the pipes. The higher velocity gas coming out at the split will run into the slower moving gases in the split.

"Less restrictive" can be an illusion if just going off of pipe diameter. It's all about velocity. Too large of an exhaust system can actually create back pressure because the engine has to push the larger volume of air out of it's way.

This is more of an issue with N/A engines, and not so much with turbocharged. The pipe sizing there would be on the ridiculous side once it became an issue.

But for this application, I doubt it is going to really make a difference either way. Ideally though, the Y split tubing would be slightly smaller than the feed pipe to the Y. That way the velocity of the exiting gases is maintained.

Also consider the gases cool the farther away from the engine they get, further slowing them down. That's why a lot of oem exhausts get slightly smaller as the pipe gets to the rear of the vehicle. They design it so the gases keep moving, for the best fuel economy.

Considering the amount of power that is put out, given the relatively small piping compared to yesterday's cars, it's obvious the engineers have done their research. The power is more than double, even triple in some cases 1980's 4 cylinders, and the exhaust pipes are the same size or smaller.
 

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2021 Forester Sport
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here we go.
Nice setup, May I ask approximately how much does the complete setup cost to covert to dual exhaust?
What parts are included in the dual exhaust setup?
I just purchased a 2021 sport and looking into dual exhaust.
Does it take a long time to get the dual exhaust bumper from Japan?
Did you do the install yourself, or had it done by someone else?

Thanks
 

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2021 Forester Sport
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57734 SJ320 Rear bumper guard
only getting this from japan. plus you need exhaust heat shield front 15+ STI or XT left side. 59024SG002.

View attachment 559436
Hi Ace,

Is this what you ordered?


edit: nvm some reason its stuck on 2022 trim. Def not the right part. Im curious where you ordered the dual exit from?

Thanks.
 
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