('14-'18) Purpose of dual exhaust? - Page 2 - Subaru Forester Owners Forum
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post #16 of 46 (permalink) Old 03-04-2014, 05:09 PM
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Just not enough interest to learn about these cars that would have done this in general.


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post #17 of 46 (permalink) Old 03-04-2014, 05:54 PM
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Originally Posted by Miniata View Post
Glad to hear Subaru came to their senses and went back to a single exit exhaust, at least on some models.
Not sure about senses, my guess it was also a beancounter driven move so save cost and weight.

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post #18 of 46 (permalink) Old 03-05-2014, 05:37 AM
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Originally Posted by Blackheart View Post
Here is the best quote from that link:

"Don't be fooled, though, as some dual exhaust systems are actually single exhaust, as a few manufacturers use just one manifold and split the exhaust pipe after the muffler. From behind the car you see two tailpipes, but if you follow them forward, you'll find just one pipe and one manifold. There is no horsepower advantage to a system like this."

THAT describes the Forester's dual system. It's more expensive than a single exhaust, and adds no power. So, it was apparently determined to be esthetically pleasing, perhaps using cues from the "balanced" handling marketing ideas, and, someone finally decided it wasn't worth it to put this faux-dual system on any more.
Not true for my 2012, there is a Y split before the two mufflers. Though I do prefer the single exhaust of the 2014.
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post #19 of 46 (permalink) Old 03-05-2014, 05:54 AM
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Not true for my 2012, there is a Y split before the two mufflers. Though I do prefer the single exhaust of the 2014.
It's still just a single exhaust - one exhaust manifold. The "faux dual exhaust" is cosmetic; more marketing than engineering.

My '10 is exactly the same way.
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post #20 of 46 (permalink) Old 03-05-2014, 06:27 AM
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There is other reasoning besides cosmetics behind dual exhausts.

Dual exhausts having two mufflers permit higher gas flow while at the same time have lower exhaust sound level.

Symmetry is, obviously, the "cosmetic" component of the design. Humans... and living things in general are symmetrical things where symmetry is a defining component of beauty. It only follows we define our cars similarly.

Also consider the fact that the entire rest of a car is symmetrical. A single exhaust, therefore, stands out as a major "wart" in an otherwise harmonious visual package. There is more than one reason the grapefruit-shooting fart can is ugly besides its sound.
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post #21 of 46 (permalink) Old 03-05-2014, 06:38 AM
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There is other reasoning besides cosmetics behind dual exhausts.

Dual exhausts having two mufflers permit higher gas flow while at the same time have lower exhaust sound level.

Symmetry is, obviously, the "cosmetic" component of the design. Humans... and living things in general are symmetrical things where symmetry is a defining component of beauty. It only follows we define our cars similarly.

Also consider the fact that the entire rest of a car is symmetrical. A single exhaust, therefore, stands out as a major "wart" in an otherwise harmonious visual package. There is more than one reason the grapefruit-shooting fart can is ugly besides its sound.
I love having dual exhaust it just looks right.

Yes it may be for aesthetics but it would look off if it only had one tip (at least on the SH)
My foz with dual 4" tips

DSC_0852 by Puzzles Photography, on Flickr


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post #22 of 46 (permalink) Old 03-05-2014, 06:40 AM
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In their Spring 2008 Drive magazine, Subaru claims to have introduced dual mufflers to the 2009 Forester to reduce back pressure and noise. Must have found a better muffler for the 2014 versions.
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post #23 of 46 (permalink) Old 03-07-2014, 06:53 PM
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Could it have something to do with the PZEV models?

Also, it definitely looks way cooler. But if it's functionally useless, why wouldn't they at least make it a proper dual exhaust and bump the performance along with the visual?
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post #24 of 46 (permalink) Old 03-11-2014, 09:16 PM
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Could it have something to do with the PZEV models?

Also, it definitely looks way cooler. But if it's functionally useless, why wouldn't they at least make it a proper dual exhaust and bump the performance along with the visual?
Because believe it or not the poor 4 popper needs some back pressure to make any torque. One thing these boxers are good for is better torque than typical inline designs.
Personally i enjoy the dual tips. The rest of my 2012 felt cheap (the doors seemed made of tin cans) but the exaust tips made it more appealing. Now if only they'd figure a way to make a Forester/Impreza that didn't shock the hell out of me EVERY time i get out....oh wait they did.....the 2014's. Maybe they integrated a grounding rod as yet unseen.....

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post #25 of 46 (permalink) Old 03-11-2014, 09:18 PM
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That's when its time for a new car.... Go to a automatic touchless car wash with under body blast at least once a month and you will be surprised how long things last....
Or move some where warmer ;)


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post #26 of 46 (permalink) Old 03-18-2014, 08:46 AM
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Some years ago I was talking to a Borla engineer while trying to improve the output of a Chevy 350HD. He told me that the 350 didn't flow enough gas through a 2.5 inch exhaust to need a dual exhaust-at least while using one of their mufflers (which flowed the same as a straight pipe).

So if a 5.7 doesn't flow enough for a single (2.5 inch) pipe, I kinda doubt a normally aspirated 2.5 needs 2 pipes. Turbo may be another story.
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post #27 of 46 (permalink) Old 04-02-2014, 06:01 AM
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I think other than maybe very exotic(and expensive) cars,manufacturers don't want the expense of two catalytic converters and don't want to have to design the underchassis room for two cats just to have true dual exhausts.I like the looks of my 2012 dual exhaust outputs but don't have any delusions that it helps powerwise.
I believe when they started putting cats on all cars it was pretty much the end of true dual exhausts.

Also other than with a dual turbo,the exhaust is combined for the turbo so it's hard to imagine any benefit from then splitting it back up for dual exhausts
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post #28 of 46 (permalink) Old 04-02-2014, 07:18 AM
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Originally Posted by CinderBlock View Post
The Forester's dual exhaust is a fake??? How sad. If an engine has 5 or less cylinders or an I6, it should be single exhaust. A vehicle with a V6 or has 8 or more cylinders, it should be a 'true' dual exhaust with an 'X' pipe. Anything turbo should have 1. But should a manufacturer put a dual exhaust on, it should at least be functional and not a fake. /End rant.
Actually, it depends on what you mean by fake. To me fake suggests that one of them is a non-functional dummy. Both exhausts and tail pipes are functional, just not in the way performance enthusiasts think of dual exhausts. The exhaust headers run to a single exhaust pipe which splits mid-vehicle to separate exhausts and tail pipes. A true dual exhaust would have separate pipes running from the manifolds to separate exhausts at the rear. So, not fake, just not a true performance split-exhaust system. My '14 has two functioning exhausts with tail pipes so technically, it is a dual exhaust system.
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post #29 of 46 (permalink) Old 04-02-2014, 01:11 PM
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I think the dual exhaust setup is to improve the departure angle. Two small mufflers instead of one large one make for better clearance. If so then it's not a fake, it just has a different purpose than what you might assume a dual exhaust to have.

Steve

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post #30 of 46 (permalink) Old 04-15-2014, 07:28 PM
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2.5L Aftermarket Duals

So, are there any aftermarket manufacturers that are making or will eventually make a dual (exit) system for the '14 and '15 non XT's? Seems like they would since the bumper cover is already cut out for it. I feel certain that they'd sell well to us symmetrical loving non-turbo owners.
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  Subaru Forester Owners Forum > Technical Forums and Vehicle Assistance > Engine and Exhaust > FB25 - 2.5L Non-Turbo (2011- 2018)

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