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Old 09-06-2006, 03:34 AM   #1
Kostamojen
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Arrow Stock N/A exhaust diagrams (for the curious and those who need to know) 93-06 years

Figured i'd start a new thread with these...

I wanted to show the difference in some of the N/A exhausts over the last couple years (amazingly, there are a couple variants since 2005!)

First off, the stock exhaust diagram we recognize for Imprezas since 1993 (sans the single-port 2.2's, I can get that one later if requested):



Secondly, the PZEV motor (2.5) from the 2004 and 2005 year legacy's. Note the single port headers which are actually the same as the 2001-04 H6 headers!:

(2004)


(2005)


And finally, the most interesting of the bunch, the current 06 exhaust. It was brought over from some of the JDM motors I believe. Equal length headers, almost a completly new setup... Requires a different oil pan to use, and I have no clue what the diameters are for the piping either, but its pretty interesting:



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Old 09-06-2006, 03:48 AM   #2
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Do you know how thick of the piping per say per year? I have an MY05 RS and just wondering what's the size of my stock piping.
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Old 09-06-2006, 04:13 AM   #3
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Quote:
Originally Posted by slayers_x View Post
Do you know how thick of the piping per say per year? I have an MY05 RS and just wondering what's the size of my stock piping.
Which part?
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Old 09-06-2006, 04:17 AM   #4
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MY05 2.5RS midpipe + MY05 2.5RS exhaust + MY05 2.5RS exhaust TIP
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Old 09-06-2006, 04:35 AM   #5
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This looks quite similar to the EL header for the JDM Outback 2.5i I posted last year.

Interesting how the secondary passes the passenger side head like a turbo header. I wonder if it will clear the usual n/a crossmembers because from the diagram it doesn't look like it would pass underneath. Did the 2.5i crossmember change from '05 to '06?

Last edited by redwagon; 09-06-2006 at 04:41 AM.
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Old 09-06-2006, 02:33 PM   #6
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Interesting that the H-6 and the 2.5L use the same headers for a couple years there. I wonder which engine they're optimized for - the flow requirements and primary length tuning would be vastly different for a ~170hp 2.5L H-4 and a 212hp 3.0L H-6.

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Old 09-06-2006, 02:59 PM   #7
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Quote:
Originally Posted by slayers_x View Post
MY05 2.5RS midpipe + MY05 2.5RS exhaust + MY05 2.5RS exhaust TIP
Go get a ruler and crawl under your car man
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Old 09-06-2006, 03:04 PM   #8
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Quote:
Originally Posted by redwagon View Post
This looks quite similar to the EL header for the JDM Outback 2.5i I posted last year.

Interesting how the secondary passes the passenger side head like a turbo header. I wonder if it will clear the usual n/a crossmembers because from the diagram it doesn't look like it would pass underneath. Did the 2.5i crossmember change from '05 to '06?
The crossmembers havent changed I dont thing for the N/A models, but im not sure on that... Ill have to check the service manual.

But it sure does look like SOA adopted that whole JDM EJ25 for the 2006 model year for the 2.5i models... Its SOHC with the i-active and the equal length exhaust... what were the power numbers on the JDM model?
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Old 09-06-2006, 03:23 PM   #9
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Alright, I checked the crossmember, its the same. The only difference in the 06's is that there is a redesigned "helper" piece above the cross plate that looks a bit more substantial... Might be a worthwhile upgrade.
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Old 09-06-2006, 07:04 PM   #10
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Quote:
Originally Posted by Patrick Olsen View Post
Interesting that the H-6 and the 2.5L use the same headers for a couple years there. I wonder which engine they're optimized for - the flow requirements and primary length tuning would be vastly different for a ~170hp 2.5L H-4 and a 212hp 3.0L H-6.

Pat Olsen
'97 Legacy 2.5GT sedan
An even better question: where are the primaries and collectors?
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Old 09-06-2006, 07:06 PM   #11
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Quote:
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An even better question: where are the primaries and collectors?
Single port heads. The only "collector" is where that cat is located.
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Old 09-07-2006, 02:04 AM   #12
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Quote:
Originally Posted by Kostamojen View Post
The crossmembers havent changed I dont thing for the N/A models, but im not sure on that... Ill have to check the service manual.
Ah, that's nice to know. Thanks.

Quote:
Originally Posted by Kostamojen View Post
But it sure does look like SOA adopted that whole JDM EJ25 for the 2006 model year for the 2.5i models... Its SOHC with the i-active and the equal length exhaust... what were the power numbers on the JDM model?
The longblock I bought (the one in the image posted above) did not have the i-active valvetrain. I found another one which appears to have the AVLS system:

That header looks a lot more like the line diagram you posted. They are claiming 177ps and 23.4kg/m from this unit. I guess that this the current unit and mine is now last year's. Mine was rated at the usual 165ps and 23.0kg/m so it looks on the surface that the power gain has nothing to do with the intake or header...
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Old 09-07-2006, 03:42 AM   #13
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You are right, the header design is completely different... The first one has a flange BEFORE the first cat, while the new one has the cat before the flange.

BTW, PS doesnt convert exactly over to HP, which makes this even more odd...
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Old 09-07-2006, 03:50 AM   #14
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+
http://www.subaru.co.jp/legacy/b4/me.../08/index.html

Now im just confused...

And notice the 190ps 2.0r has the exhaust that isnt like the one we go :

http://www.subaru.co.jp/legacy/b4/me.../07/index.html
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Old 09-07-2006, 04:30 AM   #15
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God damn, I have no clue where to find better photos of that other non-us equal length header exhaust... (ive been searching for like an hour)
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Old 09-07-2006, 06:51 AM   #16
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I sometimes get lucky searching the engine ads on auction.yahoo.co.jp or google.jp, but not this time!

Still, curiosity value aside, I don't see how this helps us. The regular EJ25 and the AVLS one have a very similar EL header, and the same intake manifold bar the EGR plumbing. The AVLS version makes 12ps more than the plain-jane version. I think the 12ps is from different cam profiles and maybe different porting, not the header. If the plain-jane EJ25 makes about the same power whether it has the USDM type intake manifold and header on it or the new stuff, then what's the point of retrofitting it?
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Old 09-07-2006, 01:17 PM   #17
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I have installed the exhaust manifold like the JDM 190-ps one when I finished the 2L DOHC engine (1991 JDM heads) for my wife's car (1997 EUDM Legacy 2.0 SOHC AWD).



Engine has a lot of torque low down and a great top end. Just middle range seems to suffer a bit, but maybe that's because intake manifold (1996 USDM EJ25 DOHC version), exhaust manifold (2005 EUDM EJ202) and engine management (1997 EUDM EJ20) are not matched.

Also seems to have a resonance around 3500 rpm which is annoying at highway speeds.



Anyway, it bolted straight up, I also had the front pipe with cat. Modified it to fit a modified 2.5 inch Impreza WRX STI exhaust (center and rear section). No problems clearing the front cross member though. Just the engine undercover had to be cut up a bit to clear the manifold.
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Old 09-07-2006, 02:54 PM   #18
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Quote:
Originally Posted by Marnix View Post
I have installed the exhaust manifold like the JDM 190-ps one when I finished the 2L DOHC engine (1991 JDM heads) for my wife's car (1997 EUDM Legacy 2.0 SOHC AWD).



Engine has a lot of torque low down and a great top end. Just middle range seems to suffer a bit, but maybe that's because intake manifold (1996 USDM EJ25 DOHC version), exhaust manifold (2005 EUDM EJ202) and engine management (1997 EUDM EJ20) are not matched.

Also seems to have a resonance around 3500 rpm which is annoying at highway speeds.



Anyway, it bolted straight up, I also had the front pipe with cat. Modified it to fit a modified 2.5 inch Impreza WRX STI exhaust (center and rear section). No problems clearing the front cross member though. Just the engine undercover had to be cut up a bit to clear the manifold.
By any chance can you get any photos of it??? I cant find anything in terms of real images of it anywhere...

As far as how the JDM one that is different might be "better", I think it would make a great start for a custom exhaust since it has a flange BEFORE the first cat...

You could have a high flow cat put after that flange with larger piping all the way to the axleback and have all of it completely bolt-on-able and with the 4-1 equal length header (which is what alot of aftermarket headers for NA cars are TRYING to do anyway).
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Old 09-16-2006, 12:53 PM   #19
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Here's another oddity I stumbled across:



JDM BE5
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Old 09-17-2006, 02:52 AM   #20
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That could make for an interesting custom exhaust... But it sure is odd. Which motor was it for on the BE5?
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Old 09-17-2006, 03:00 AM   #21
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I dunno mate. It's up for sale on Yahoo Japan but the seller only notes it's from a Legacy RS. The stated year is '99. My best guess is that it had the 190ps EJ20R unit in it. The real difference between this and the regular style header is the longer primaries. That could be to help fill out the torque curve on the revvy little EJ20R...
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Old 10-13-2006, 07:19 AM   #22
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Quote:
Originally Posted by Kostamojen View Post


I just saw this system irl under an '06 2.0 Forester here in Taiwan. It would need the STi type oilpan as we guessed, but it looks like it would clear the usual N/A crossmembers.
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Old 10-18-2006, 04:50 AM   #23
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It does clear the N/A crossmembers. You do need the newer style oil pan, I have a few used ones lying around.

I will see if I can take pictures later today, as I'm using my wife's car today. Had to have it cleaned inside and out at work, and also had to burn the 'rags' from the combustion chamber, so I gave it a good run on the German Autobahn today (210 kph on the clock at just over 6000 rpm).
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Old 06-04-2008, 07:08 PM   #24
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I'm gonna bump this thread to ask a quick, probably easy question: is an NA catback exhaust mostly the same as a turbo exhaust except for the flange being rotated the wrong way? I can't tell which way the flange is shown in the diagram up top.

Here's the deal: I have what I think is an NA Greddy EVO 2 catback that I want to sell, and I want to make sure it'll fit an NA Impreza before I sell it to someone. I bought it from someone who said it was the one for a WRX, but when I got it, the piping was too small to be a turbo exhaust. Also, I test fitted it just for kicks, and the flange was rotated about 90 degrees or so at a different angle than my WRX downpipe.

I just need some insight on what the differences are between the WRX/STi and an NA catback...that way I can figure out what this exhaust is for. Thanks in advance...

-E
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Old 06-05-2008, 03:13 PM   #25
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No one has any insight on my problem?
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