2nd cat issue!!!!

[GEE-OTTO]

I am swapping my the exhaust manifold in my 2008 2.5 NA Legacy to a LGT OEM exhaust manifold. It fits fine since they are the same engine but before button it up i have a question. The stock manifold had a cat built in to the manifold as well as a secondary cat about 16 inches down stream on the manifold mid pipe flange. Now the LGT manifold has a 22 mm bung already in place before the 2 bolt flange. I was wondering if that second cat is sufficient to work with the two existing O2 sensors? Or rather is that even a cat or a quasi cat/muffler thing for sound control? if i can use that as the cat I wont buy one if I can i will use that and just chop the 3 bolt flange off and put a 2 bolt flange to mate it to the LGT manifold?!

[GEE-OTTO]

anyone?

[j255c]

As discussed before, no one has the answer to this because its a stupid idea.

[j255c]

But, here you go.

 

http://mrtperformance.com.au/forums/showthread.php?t=484

 

I'd like to emphasize a couple of points from this reference:

 

"However, no matter what you do, it is never going to sound exactly like a WRX unless you fit a turbo. A turbo adds a separate dynamic to the entire flow of an exhaust system and changes the note."

 

"You will never make a Naturally Aspirated Impreza sound exactly like a WRX. However, you can still achieve a nice boxer note. While fitting unequal length headers will give you the closest end result, they are very expensive to import and the improvement both in performance and note over a CAT-Back system with standard headers is simply not justified.

 

I recommend starting with a CAT-Back system and modifying your induction system and seeing if this suits your needs."

[GEE-OTTO]

But, here you go.

 

http://mrtperformance.com.au/forums/showthread.php?t=484

 

I'd like to emphasize a couple of points from this reference:

 

"However, no matter what you do, it is never going to sound exactly like a WRX unless you fit a turbo. A turbo adds a separate dynamic to the entire flow of an exhaust system and changes the note."

 

"You will never make a Naturally Aspirated Impreza sound exactly like a WRX. However, you can still achieve a nice boxer note. While fitting unequal length headers will give you the closest end result, they are very expensive to import and the improvement both in performance and note over a CAT-Back system with standard headers is simply not justified.

 

I recommend starting with a CAT-Back system and modifying your induction system and seeing if this suits your needs."

 

 

If I wanted a WRX i would have bought a WRX if I wanted my car to sound like a turbo I would have bought a LGT. YOu talk to me like I rant and rave about power gains with this mod. I tell N/A guys daily that power IS NEVER the goal when dealing with the EJ253 so you need to realize who you are responding to before you try to get "holier than thou" on here:mad:

 

And also If you have read I am doing this as part of a write up for alt Legacy N/a Exhausts so the guy that is thinking about exhaust options may not have to spend big $$$ if he can and still get a good end result AS well as putting a borla header setup on my car so while you think this is stupid in the end i hope to show people that the only stupid people are people like you that do nothing helpful and try to shame people who actually arent scared to push the envelope of innovation for 2.5i N/A guys

 

And ive read that post a LONG time ago

[j255c]

Ok, ill leave you alone have fun.

[korpsepatrol]

so you need to realize who you are responding to before you try to get "holier than thou" on here:mad:

 

So um who are you?

[bugblatterbeast]

The stock manifold had a cat built in to the manifold as well as a secondary cat about 16 inches down stream on the manifold mid pipe flange.

 

there is no cat in the manifold. there is a pre-cat in the up-pipe on 05-06

[bugblatterbeast]

I am doing this as part of a write up for alt Legacy N/a Exhausts so the guy that is thinking about exhaust options may not have to spend big $$$ if he can and still get a good end result

 

what exactly do you mean by a good end result? NA cars depend on exhaust manifold resonances much more than turbo cars. your stock manifolds will make more output on your setup. if a different exhaust note is your goal and you want to do it cheap, why not just modify a stock header to make it less symmetric.

 

I'm not terribly familiar with the NA setup but I'm going to guess that you have two small pre-cats (one per bank) and a big main one. if your goal is more rumble (and cheap), just knock the core out of one of the pre cats.

[GEE-OTTO]

there is no cat in the manifold. there is a pre-cat in the up-pipe on 05-06

There is a cat in the 2.5i manifold read again

[bugblatterbeast]

There is a cat in the 2.5i manifold read again

 

since you have a 2.5i, one would naturally assume that you were asking about the LGT manifold. your reference to a stock manifold provides no indication if you are referring to a stock ej253 manifold or ej255. you obviously don't need anyone's help. just slap the LGT manifold on and have fun.

[GEE-OTTO]

what exactly do you mean by a good end result? NA cars depend on exhaust manifold resonances much more than turbo cars. your stock manifolds will make more output on your setup. if a different exhaust note is your goal and you want to do it cheap, why not just modify a stock header to make it less symmetric.

 

I'm not terribly familiar with the NA setup but I'm going to guess that you have two small pre-cats (one per bank) and a big main one. if your goal is more rumble (and cheap), just knock the core out of one of the pre cats.

 

Thanks for that advice and if it were the case I wouldnt go that route not because I think it is bad but if you know anything about welding and such you know that cast iron is a pain or rather can be a pain to cut and reweld and have it retain its integrity. The N/A manifold has one Cat that is read by the O2 sensors that is built into the stock manifold. $75 for a LGT stock manifold that bolts right to my car is a lot cheaper, less hassle, and more sound than doing it that way. Plus I dont want to gut the cat, which is why I bought Thunderbolt OBDII HFC it was the new bungs for the two sensors in place so after the LGT manifold flange that will be welded inline from a flex joint ( to keep vibration out of cabin) then a 2.25 inch pipe to a 18 resonator which splits off to mufflers. That should give you a better idea and here is a sound clip of a 2.5i Impreza ( same engine EJ253 ) with the exact same setup ( manifold wise he used a WRX turbo manifold im useing LGT) as i will have let me know how good or bad this sounds and you be the judge if what i am doing is stupid

 

[ame=http://www.youtube.com/watch?v=S87In-g7ZVM]YouTube - Impreza 2.5i WRX Header Stromung Cat-Back[/ame]

[GEE-OTTO]

So um who are you?

 

Good Question no one special or important just a regular Subbie guy trying to show the N/A side of things that there are other ways to get a defferent exhaust note nothing more I don't claim to be the all knowing scbooy guy or w/e which is why I asked what seemed to be a simple question about a second cat