Jump to content
LegacyGT.com

2.5i Header to Tail pipe


Recommended Posts

Hello folks it is your old pal GEE OTTO here to post about the mythical and elusive LGT stock manifold modified to fit the 2.5i platform and other useful information about the rest of the exhaust.

 

Many years and many, many hours of research and trial and error were put into getting this done right. I made a thread 2 or 3 years ago to float the idea and gather feedback, which came in the form of positive and negative responses. I understand both sides ;).

 

So first let’s clear up some complete garbage about this project/mod:

1. You don't lose bottom end power

2. You don't lose top end power

3. Your cars acceleration is more linear

4. You car sounds like a stock LGT afterwards

5. It does not impede the oil filter in fact it makes oil changes 10x easier :)

6. Your second cat IS sufficient to keep the CEL off and your fuel mileage the same

7. It will not melt your water pump outlet

8. It does fit under the stock splash tray with plenty room to spare

9. You do not get the sewing machine sound under load

10. You don't have to fab a new mid-pipe

11. You only have to extend your rear (gray) O2 sensor

12. The LGT manifold fits the EJ253

13. The stock flange is a 3 bolt 2.25" NOT 2.5" flange !

 

In terms of difficulty this would be a 7/10. You will need these parts:

 

  • 05+ LGT/WRX/STi manifold
  • 2.25" three bolt flange with ROUND holes and a set of Grimmspeed THICK cross-pipe to elbow gaskets see my diagram below:http://i144.photobucket.com/albums/r182/GEE-OTTO/Flangeissue-1.jpg
  • A Casper Electronics Rear (gray) 36" O2 extension
  • Two standard O2 bungs
  • A thick 2.25 inch three bolt gasket

Photo of the parts (notice the thick GrimmSpeed gaskets installed btwn the cross pipe and collectors)

http://i144.photobucket.com/albums/r182/GEE-OTTO/IMG_0515.jpg

 

The most difficult part of this process is finding a shop that will chop and weld the manifold. Cast Steel scares many a welder, so ask around and explain to them what you want done, take a picture with you :).

 

So far LM24 in the Tristate area and Mach V in the greater DC Metro area will do it for a good price and do it right. Once you find a shop they will be able to do the entire project for you.

 

Some tips from me after three UEL attempts:

 

Try not to splice the O2 sensor(s) if you have to move the AFR sensor (orange) reroute the wiring harness back through the intake manifold and down the back of the engine first! Then connect the orange and place it where you or your fabricator sees fit. If you do splice them make sure to use the proper braided wire not the solid copper stuff.

 

Buy the rear (gray) O2 extension! Trust me there is nothing better than having a Bolt on UEL setup that you can swap out to your stock setup with the turn of a wrench and unplugging of a sensor. There is also much to be said about peace of mind :)

 

DO not rush the process! Don't settle for a old beat up Stock manifold, I bought a EJ20K manifold it was in bad shape but cheap it wouldn't even fit my block, and I ruined the bolt flange b/c it was so rusted together I had to use a torch and cutting wheel to separate the three parts. Well trust me when I say: grey iron doesn't like the heat an Oxy/Acetylene torch puts out:lol:

 

Keep a look out for a clean EJ255/7 (05+) stock manifold. Also buy a good thick flange as well for the new connection to your stock mid-pipe. You will find plenty of 1/4" flanges but you want at least 3/8" and preferably a 1/2" or greater. This insures during the welding process you don't experience any warping.

 

Do some research on the rest of your exhaust well ahead of time as well. I like mellow tones and overall quiet operation SO I went with stock LGT cans and my stock Y pipe. For now this setup is as quiet as the stock 2.5i system. Most of us that have/will done/do this mod want to have something to show for it so naturally a CBE is in the mix of future additions.

 

I would suggest the more tame SPT/BOSAL exhaust first if you can't find that look for an exhaust with a resonated mid-pipe like the Invidia Q300, this is essential as things get loud once you go un-resonated. Custom is an option but I would stick to 2.5 inch piping and neck down to 2 inch for the split to the mufflers.

 

I say that b/c typically a shop will fabricate the exhaust with thin walled mild steel instead of thicker 304 grade steel. Thinner steel has issues like, poor corrosion resistance, emitting mechanical sounds, lower crush tolerance, and the interior has a higher coefficient of friction. However it is cost effective and with a few coats of Hi-Temp header paint you will have a durable custom setup.

 

I would also go for an 18" minimum resonator, you want to go with a double walled, fiberglass packed resonator. If you cheap out on this component you will suffer from drone and rasp, so look at brands like Vibrant, Thrush, Borla, etc.

 

Along with custom piping comes your choice of mufflers I would avoid a straight through muffler i.e. FlowMaster 40's or Super 44's, cheap 115mm melon cannons you find on eBay or cheap exhaust shops. Instead look for chambered and well packed mufflers like a Flowmaster 60 Series, Thrush Hush Super Turbo, MagnaFlow Universals or any other well flowing well insulated muffler.

 

 

 

 

And now some pictures of my recently completed setup as reference for your own project should you choose to follow.

http://i144.photobucket.com/albums/r182/GEE-OTTO/ge_hdr1.jpg

http://i144.photobucket.com/albums/r182/GEE-OTTO/ge_hdr4.jpg

http://i144.photobucket.com/albums/r182/GEE-OTTO/ge_hdr5.jpg

http://i144.photobucket.com/albums/r182/GEE-OTTO/ge_hdr3.jpg

http://i144.photobucket.com/albums/r182/GEE-OTTO/ge_hdr2.jpg

 

As you can see the stock splash shield fits perfectly and will not melt. The stock size oil filter clears easily. You can also see how I positioned the rear O2 sensor so it isn't directly exposed to road elements (snow, rain, salt, debris). The front sensor is placed in a similar fashion for the same reasons and because there isn't much slack with the connector in the stock location under the intake manifold.

 

Reflections:

Keep an open mind about the end result and be willing to change components as needed to achieve your desired effect.

 

Be clear when approaching a shop or welder to do this project, print my pictures, take them with you, show them. This is a big part of getting a yes versus a “nah I can’t do that.”

 

I wish I went with this setup three years ago it is as quiet as stock and I have the option to go LGT CBE or back to stock at anytime. Oil changes are easier and there is no degradation in fuel mileage or vehicle behavior. Also this setup is solid, compact and durable.

Link to comment
Share on other sites

do you have a dyno before and after you can post just for the hell of it. Or did u do this for sound?

 

My car got hit and it might be totaled BUT my plans are to get it tuned via OS. I did this mod initially b/c i love the boxer note but when it comes to efficiency this mod makes more and more sense.

 

I had planned a tuning session at EFI but thats on hold until my cars fate is determined by the frame jig. However numerically, I have increased fuel mileage.

Link to comment
Share on other sites

Great post Otto. Sorry to hear about your car. After reading the description of the damage I was wishing it was a year or two older so that they would total it. Hate to see you in this situation bro. Sucks bad.:mad::mad::mad:

If something is less efficient how would you have increased mileage? Are you CERTAIN its not just the metal effect? Many people add hydrogen systems and all sorts of things that make no real difference and report differences - mostly because they change their driving habits ever so slightly.

I'm totally onboard every sound claim you will make about it sounding better than a stock 2.5i but I would like to see some real numbers and a tune results (to varify no loss in the low range) so I can cosign the mileage bump.

Link to comment
Share on other sites

Great post Otto. Sorry to hear about your car. After reading the description of the damage I was wishing it was a year or two older so that they would total it. Hate to see you in this situation bro. Sucks bad.:mad::mad::mad:

If something is less efficient how would you have increased mileage? Are you CERTAIN its not just the metal effect? Many people add hydrogen systems and all sorts of things that make no real difference and report differences - mostly because they change their driving habits ever so slightly.

I'm totally onboard every sound claim you will make about it sounding better than a stock 2.5i but I would like to see some real numbers and a tune results (to varify no loss in the low range) so I can cosign the mileage bump.

 

 

Cognitive Dissonance;)

 

Scavenging is siphoning plain and simple. The ideas is you create a manifold that aides the siphoning effect as much as possible given the application. For a DD passenger car a tuned EL header wont give you any better qualitative results than a UEL.

 

If you read in my long conversion thread the stock EL manifold has runners that are 25" , 25" , 21" and 19" in length thats 7.5 feet of travel just to get to the first restriction point, the cat. Then 2.5 more feet until the second cat. Keep in mind that is not a linear path of travel.

 

My logic was/is simple improve exhaust flow. Eliminating a catalytic converter and creating a more linear path for gases to flow away from the combustion chamber was the logical approach. You can't have a decrease in efficiency by making the basic process of exhausting more efficient.

 

I run this UEL manifold with the stock CBE it sounds no different than a stock 2.5 LGT with a stock CBE. Which is fairly similar to a stock 2.5i at idle and mid range rpms.

Link to comment
Share on other sites

it seem like you know alot about this. Have you looked into a tuned set of headers for are car and use of a termination box?

 

LaChute Performance makes the closed thing to a Tuned EL besides TWE both are great headers but both require a full custom exhaust as they do not utilize stock locations.

 

For my Legacy i don't need nor drive my car in a manner that such a magnificent header would do much good. If i had a track car or was heavy into autoX i would jump at them:)

Link to comment
Share on other sites

GEE-OTTO, I found some 05' GTSpec UEL headers for sale by another member. Since you seem to be quite the exhaust guru, would you be able to tell me if they would fit my 08' 2.5i? http://legacygt.com/forums/attachment.php?attachmentid=102350&d=1310252638
Link to comment
Share on other sites

They will fit but that collector flange will come really close to hitting the lower crossmember. The beauty is they are slip fitted so you can pull them apart and bolt them on or just bolt on the collector side for the mock fit to determine where to cut
Link to comment
Share on other sites

  • 3 weeks later...
I also have seen two or three 2005 owners with some issues so I would like to add that the 2005 2.5i shares the dimensions of a 98-2007 Impreza they have a shorter mid pipe section than a 2006+ Legacy 2.5i or 2008+ Impreza because of the turbo two piece down pipe/mid pipe. 2006+ was when the newer mid pipe design for the N/A Legacies/OB hit the scene, it was modeled to terminate at the same place as the Turbo models "mid-pipe" ;)
Link to comment
Share on other sites

  • 2 weeks later...
  • 3 months later...

GEE-OTTO,

 

Do you know anything about increased emissions because of deleting the first cat?

The second cat is the biggest and I don't know if the first cat contributes al lot.

What do you think? Here in the Netherlands emission rules are rather strickt.

Link to comment
Share on other sites

GEE-OTTO,

 

Do you know anything about increased emissions because of deleting the first cat?

The second cat is the biggest and I don't know if the first cat contributes al lot.

What do you think? Here in the Netherlands emission rules are rather strickt.

 

 

Well here in the states ive passed my inspection twice now but im not sure how tough Netherlands rules are, the second cat is i used to further cut emissions in a stock setup so I imagine one cat is sufficient to meet US laws and the second is for Subaru to legally claim the car a s PZEV or ULEV

Link to comment
Share on other sites

Thanks for the quick reply. I can always get it tested at a garage when the mod is done.

If it doesn't meet the requirements I can always do a 15 min. header swap before having it inspected.

That's why this method is so great! :-)

Link to comment
Share on other sites

Thanks for the quick reply. I can always get it tested at a garage when the mod is done.

If it doesn't meet the requirements I can always do a 15 min. header swap before having it inspected.

That's why this method is so great! :-)

 

EXACTLY i swapped once then the second time i forgot to swap but it still passed

Link to comment
Share on other sites

Just one more question. ;-)

 

Where did you get your 3 bolt 2,25" flange?

I can find them myself, but not here in the Netherlands.

So...I'd have to guess which one would be ok.

If I order the same one as you I'm save. :-)

 

EDIT: Does it happen to be from "Vibrant"? I can easily get those. They also sell the corresponding gasket.

Link to comment
Share on other sites

Just one more question. ;-)

 

Where did you get your 3 bolt 2,25" flange?

I can find them myself, but not here in the Netherlands.

So...I'd have to guess which one would be ok.

If I order the same one as you I'm save. :-)

 

EDIT: Does it happen to be from "Vibrant"? I can easily get those. They also sell the corresponding gasket.

 

I bought the vibrant 2.25" three hole flange like you found BUT if you notice it has long slotted holes so the studs of your stock mid pipe will slip and cause a leak you need to order your flange from these folks:

 

http://www.spdexhaust.com/3BoltB.html

 

You want this one (just put this in the email when ordering) :

 

F225-3CNC

here is the contact info :

 

http://www.spdexhaust.com/ContactsB.html

 

I bought their flange to fix my problems :)

Link to comment
Share on other sites

Great! Thanks a lot!

I've contacted the right away. Let's hope they ship to the Netherlands.

 

I already read your warning about long slotted holes, but thanks for reminding me.

That's why I still asked about Vibrant. They do have flanges with round holes.

http://vibrantperformance.com/catalog/product_info.php?cPath=1022_1122_1154&products_id=146

But the bolt circle is bigger than the one you used...

Link to comment
Share on other sites

Great! Thanks a lot!

I've contacted the right away. Let's hope they ship to the Netherlands.

 

I already read your warning about long slotted holes, but thanks for reminding me.

That's why I still asked about Vibrant. They do have flanges with round holes.

http://vibrantperformance.com/catalog/product_info.php?cPath=1022_1122_1154&products_id=146

But the bolt circle is bigger than the one you used...

 

Yeah that picture is actually wrong they need to update it so people don't get shafted anymore, like me :lol:

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.



×
×
  • Create New...

Important Information

Terms of Use