Question about mounting a 3" pipe into N/A

[rstimpreza]

Is it ok to install a 3" piping exhaust into N/A 2.5 Legacy?

[phi11]

i'm going to say no.

viewtopic.php?f=11&t=11403 (https://sl-i.net/FORUM/viewtopic.php?f=11&t=11403)

[httrdd]

Been there done that loved every minute of it! In my build thread in my sig you can see how much I had to extend a 3" 02 WRX Borla cat back to fit the LGT when I was running the 2.5. Also a couple of sound clips with and witout headers! :wink:

[d1giPhux]

bye bye low end. Don't run a 3" pipe.. its foolish and wasteful. Plus you will lose power.

[rstimpreza]

Right now I have Borla UEL headers with stock cat. im planning on using 3" midpipe to axleback. Is that safe without losing power?

[Airgne]

dont listen to all these naw sayers.

i have borla header, 2.5in cat delete pipe, 3in midpipe to tip.

d1gi said good by bottom end. i think not

i produced 165.7awtq at 2000rpm(have the dyno sheet to prove it) that is stock flywheel tq on the ground with 3in exhaust. oh and 167awhp with 3in exhaust. hmm i think you will be fine.

now there are somethings to think about. there are reasons i dont have 3in for the whole exhaust, and yes it has to do with flow. you loose alot of you exhaust velocity. on n/a you want some back pressure in your exhaust system, but you do not want to much.

it took me 4 exhausts to find the right combo. some n/a scoobies need 3in, just depends on the work done to the car.

[d1giPhux]

3 inch is total rice business on these cars imo. You don't need anything over 2.5 unless you have cams and heavy engine work done or forced induction. 2.25 is really sufficient enough. Your definitely going to lose low end with a 3" pipe. But really.. its up to you!

[Airgne]

you still dont prove anything by saying you will loose power its totaly rice.

explain my power, explain why muscle car ppl ask me whats in my car when they hear it. explain these things. you are just stating you opinion. the internet is full of them. back your shit up or stfu.

[anothernord]

Every thread I've ever read has stated that 2.25" is the ideal size for the 2.5 N/A Subaru engine. Sure, a 3" may sound better, but it probably isn't the best for power. However, when you're only talking about 10hp, it really isn't that big of a deal.

[httrdd]

Then my stock cat back must of been clogged with all kinds of shit! :roll: After putting the 3" on with the stock headers I picked up the low end power as well as the WOT power and after the Uel headers went on it was a great ending. I would like to see some dyno numbers to prove that this is too much flow. If going bigger is bad then why do people PNP to get the most flow?

[anothernord]

Stock exhaust size is like 1 5/8".

[phi11]

3" without supporting mods is stupid.

I lost low end w/ header, test pipe, and 2.75" pipe.

[d1giPhux]

Oh.. its no doubt you will get the boxer rumble! Not saying that.. but I'm saying that your pushing WAAAY too much exhaust out and your gonna lose low end. Its like mopeds / motorcycles. If you leave the intake on a moped completely open, and have an unrestricted exhaust.. you will lose almost all your low end and will have a hell of a time going up hills. The only way to fix that is to either restrict the exhaust, or the intake a bit. I've done it by restricting the intake.. and you get some low end back. However.. because its moving all that air.. it will just bog down. I can't prove it to you in numbers / dyno sheets.. because I don't have any. But $10 says you lose low end power. Its just what happens. I've played that game on honda's before.

[phi11]

explain my power
maybe you should explain everthing that you've done to your car,
o.p. is asking about a stock 2.5na w/3" pipe.

[Airgne]

Oh.. its no doubt you will get the boxer rumble! Not saying that.. but I'm saying that your pushing WAAAY too much exhaust out and your gonna lose low end. Its like mopeds / motorcycles. If you leave the intake on a moped completely open, and have an unrestricted exhaust.. you will lose almost all your low end and will have a hell of a time going up hills. The only way to fix that is to either restrict the exhaust, or the intake a bit. I've done it by restricting the intake.. and you get some low end back. However.. because its moving all that air.. it will just bog down. I can't prove it to you in numbers / dyno sheets.. because I don't have any. But $10 says you lose low end power. Its just what happens. I've played that game on honda's before.


did you even read my post? doesnt look like it. look at the numbers. they dont lie. until then you need to move on to a diff thread.

[Airgne]

explain my power
maybe you should explain everthing that you've done to your car,
o.p. is asking about a stock 2.5na w/3" pipe.


when i first put on the 3 in exhaust i have nothing but intake. i will have to get my number from the dyno when my house gets unpacked. i had no lose in noticable power at all.

[httrdd]

Ohh now you are in for it!

[Reason]

I have 2.5" catback, UEL stock cats, works pretty good for me. But I also have cams and a intake on top of other things.

you are just stating you opinion. the internet is full of them. back your shit up or stfu.


https://sl-i.net/FORUM/images/imported/2010/09/FacebookThumbsUppng-1.jpg Justin (http://www.facebook.com/?ref=logo#!/profile.php?id=1712240220) likes this.

[Zac]

call delta cams and ask. Unless you have a crazy cam profile and a race PnP job then they suggest a 2.5" exhaust. If not run 2.25"

[d1giPhux]

My engine definitely isn't choking.. and I run stock headers, stock cat pipe, 2.25" midpipe, 2.25" SPT exhaust. Dunno what your running under yours.. but damn you must be puttin down some power or something. My car already needs to be hella rev'ed to get some quick low end.. maybe I'm doin something wrong. What you running for an intake?

[Airgne]

I have Cobb intake. I also have delta 2000/1000 grind cams.

[d1giPhux]

Makes sense now. Gotcha!

the 2000/1000 grind for low end, right?

[Airgne]

Yes.

[Huffer]

Let's try to keep the thread on the practicalities of flange extending to a 3" exhaust for a EJ25. If you have cam related questions, head over to those threads or PM the relevant user.

In future, if anyone has proven power bragging rights (hello dyno sheet), post up the dyno sheet or link it to your MR1 thread where it should already be posted. Thanks! :)

[StatGSR]

^ problem is a dyno sheet can lie just about as much as any joe on the interwebs.... bench racing is a joke....

[rstimpreza]

Thanks for everyones opinion. My setup right now is Borla UEL headers, Stock cat., custom 2.25" midpipe and a 3" pipe Hks carbon Ti axleback exhaust. I was wondering if I can mate my stock CAT to a 3" midpipe and run with no problems like power lost.

[Airgne]

Thanks for everyones opinion. My setup right now is Borla UEL headers, Stock cat., custom 2.25" midpipe and a 3" pipe Hks carbon Ti axleback exhaust. I was wondering if I can mate my stock CAT to a 3" midpipe and run with no problems like power lost.


as for the fart can muffler, it will not sound good at all. to raspy. as for the stock cats fitting that is no. they are alot smaller. if you want a cat get a magnaflow 2.5in id cat. this will help with flow.

i did the stock cat to 3in, and it was really hard.

oh and yes my dyno sheet is in my mr1