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Old 06-15-2009, 08:41 PM   #1
Kramer3608
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Default RalliSport Racing HF Cat

If I purchased the Stainless HF Cat http://rallisportracing.com/Products.html for my 06 2.5i and paired it with the Ebay Borla replicas. Would I still get the slight performance increase and the boxer "rumble" if I were to go with the Stromung. Has anyone tried this out before and would those be the only pieces that I would need and it would basically bolt right on?. Any help/advise would be appreciated. Oh and Im assuming that the difference between the 304 stainless and aluminized steel would be corrosion protection and price
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Old 06-15-2009, 09:08 PM   #2
SUBYAWD85
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Originally Posted by Kramer3608 View Post
If I purchased the Stainless HF Cat http://rallisportracing.com/Products.html for my 06 2.5i and paired it with the Ebay Borla replicas. Would I still get the slight performance increase and the boxer "rumble" if I were to go with the Stromung. Has anyone tried this out before and would those be the only pieces that I would need and it would basically bolt right on?. Any help/advise would be appreciated. Oh and Im assuming that the difference between the 304 stainless and aluminized steel would be corrosion protection and price
UEL (unequal length) Borla = Rumble with HFC or no HFC. The header creates the rumble.

Many people have done this. Search before the flaming begins.
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Old 06-15-2009, 09:41 PM   #3
SUBYAWD85
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Also I think the Rallisport is different then the Stromung. From what I have read.. the Stromung only bolts up to a 05 Catback system. The Rallisport is designed to bolt up to the factory catback. So if you went Stromung you would have to get a 05 cat back.
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Old 06-15-2009, 09:43 PM   #4
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I have searched, I got no information on the Rallisport Cat. Which is what I wanted to know about. Whether or not I can bolt it onto the stock cat back and if it they would recommend it. I know about the UEL(rumble) and EL(more hp) headers. Oh and the flame suit has been on for a while.
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Old 06-15-2009, 09:45 PM   #5
SUBYAWD85
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Originally Posted by Kramer3608 View Post
I have searched, I got no information on the Rallisport Cat. Which is what I wanted to know about. Whether or not I can bolt it onto the stock cat back and if it they would recommend it. I know about the UEL(rumble) and EL(more hp) headers. Oh and the flame suit has been on for a while.
Are you wondering about switching from Rallisport to Stromung? Are you looking for better gains? Have you installed the UEL headers and HFC already? Whats the reason for the switch?
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Old 06-15-2009, 10:03 PM   #6
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nah, right now its completly stock and im looking to see what the best way to go would be. I was thinking the rallisport would be the easiest at least. Do you know what the downside to that would be? (leaving the stock cat back)
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Old 06-15-2009, 10:11 PM   #7
SUBYAWD85
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nah, right now its completly stock and im looking to see what the best way to go would be. I was thinking the rallisport would be the easiest at least. Do you know what the downside to that would be? (leaving the stock cat back)
No there is no downside. If you are just doing intake and exhaust and simple things like that then you dont need a HFC. It just all needs to bolt up, otherwise it will have to have some custom work done. The Borla headers dont bolt up to the stock Cat section for the 06 (as far as I know). So thats why people buy the HFC, so it bolts up. You could look on Nasioc classifieds to see if someone is selling a stock cat section from a 05 RS and use that, which is a cheap solution. Basically.. rule of thumb is.. start from the headers and work your way back. Figure out what headers you want and go from there. If you want the UEL borlas, then you are setting yourself up for an 05 setup. After Borlas you will need either an 05 HFC (rallisport or Stromung). Stromung will require an 05 catback system (midpipe and axel back exhaust) Rallisport will bolt up to your stock cat back. (I got this information from Rallisports website)IF you use your stock catback (midpipe and axelback) you can retain your stock midpipe (saving a couple hundred) and use a bolt up axel back from a WRX I believe. Correct me if Im wrong
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Old 06-16-2009, 02:52 AM   #8
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Old 06-16-2009, 04:26 AM   #9
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Rallisport Racing has some vids on youtube with 06 2.5i and stock exhaust.

Sounds like junk IMO without an aftermarket catback.
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Old 06-16-2009, 09:08 AM   #10
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Originally Posted by SUBYAWD8
IF you use your stock catback (midpipe and axelback) you can retain your stock midpipe (saving a couple hundred) and use a bolt up axel back from a WRX I believe. Correct me if Im wrong
Ok so just hunt around for a used wrx axel back or an aftermarket one for better sound quality and I should be golden. What is your opinion on alumized steel and 304 stainless. I'm assuming that stainless would last longer and the other would corrode faster (these are the option for the cat)

Thank you for the help btw
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Old 06-16-2009, 02:43 PM   #11
SUBYAWD85
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Ok so just hunt around for a used wrx axel back or an aftermarket one for better sound quality and I should be golden. What is your opinion on alumized steel and 304 stainless. I'm assuming that stainless would last longer and the other would corrode faster (these are the option for the cat)

Thank you for the help btw
Yeah, I would look around a little on the forums and make sure you can find someone who has bolted up a wrx axel back to the 2.5i before you buy it. I have been researching exhausts on here for like 3 months and still havent bought one because I want to make sure I get the right setup. I think you are right about 304 vs aluminized, but you need to take into account where you live, what the weather is like and if you would really need the stainless. I would ask some users who have purchased both to find out the difference, or call a couple muffler shops cause they are the experts. Also depending on the headers you get, the borla replicas (from ebay) are not made out of the same material as the real Borla headers. You should wrap the headers if they are not legit, but also if you have never wrapped headers, read up on that first.
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Old 06-16-2009, 02:59 PM   #12
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Originally Posted by SUBYAWD85 View Post
UEL (unequal length) Borla = Rumble with HFC or no HFC. The header creates the rumble.

Many people have done this. Search before the flaming begins.
+1 HFC will just be making powah
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Old 06-16-2009, 07:28 PM   #13
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Ya, I live in Maine so the winters blow with all the salt and sand on the roads. Another question, what is the difference between the 2.5i, WRX and STI axel back. I found some people selling a WRX and STI and I'm not quite sure what the difference between the 3 are. If there is any at all between the WRX and STI
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Old 06-16-2009, 07:31 PM   #14
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I'll probably go the Rallisport HFC route and ebay borla reps in the future, so if you can be the guinea pig for me that'll help. I was able to bolt on an 06 STi axleback with no issues, but I swapped it out after a few weeks with a stromung SS dualtip. I think Stromung said mine was made for 07 so I don't know if it'll bolt up to an 05 catback system which is why I plan to go the Rallisport route. The stromung dualtip makes the exhaust sound way better already so new headers/hfc will be icing on the cake. The STi axleback is alright, sounds better than stock but with HFC and headers it might sound raspy. There's a vid on youtube with a wagon with that setup. Listen to it and see what you think.

Oh and I took the stromung SS up to the mountains when it was snowing pretty good, and drove thru the salt and what not, then I came home and didn't wash the car for like three weeks and the exhaust was still shiny afterwards, although I didn't look at the rest of the exhaust.
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Old 06-16-2009, 07:48 PM   #15
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+1 HFC will just be making powah
A HFC on a EJ253 without cams/headwork will gain you next to nothing. you certainly wont be able to feel any difference. i promise.
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Old 06-16-2009, 08:47 PM   #16
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That the video you were talking about? I'm not a big fan of the second clip which is I guess with the headers, HFC, and Sti catback. Way to raspy/tinny for my liking.
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Old 06-16-2009, 10:12 PM   #17
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A HFC on a EJ253 without cams/headwork will gain you next to nothing. you certainly wont be able to feel any difference. i promise.
so then whats that point other than the sound?
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Old 06-16-2009, 10:32 PM   #18
SUBYAWD85
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so then whats that point other than the sound?
You get your gains from a header and a tune
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Old 06-16-2009, 10:47 PM   #19
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so then whats that point other than the sound?
unless you are building an EJ253 with cams/headwork/internals then there is really no reason. (on 06/07's you might need an 05 style catpipe to make most catbacks/headers fit, so then it could make sense econimically to get a HFC since it will be the cheapest way to make everything else fit without getting old used cats.) In terms of sound, it seems that HFC's just make it louder and more raspy. my setup has a tinny clicking sound @ higher rpm's when it's cold... think a stock cat would sound better but i do plan to do cams and some PnP on the heads/intake manifold/headers soon.
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Old 06-17-2009, 10:06 PM   #20
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A HFC on a EJ253 without cams/headwork will gain you next to nothing. you certainly wont be able to feel any difference. i promise.
To clarify are you saying that UEL headers and a HFC will gain you nothing, or just replacing a cat? Obviously, simply replacing the second cat with a HFC will gain next to nothing. However, if you are saying that replacing the factory EL headers with UEL headers and a HFC gain nothing, I would disagree. I have yet to see any hard numbers from anyone who has gone from stock to UEL plus HFC and gained zero. Even though you are replacing the factory EL with UEL, you still are completely removing the first cat and replacing the second with a better flowing one. Also, that would mean that I and everyone else with a 06+ 2.5i that has done this mod and has felt their car pull a little harder is suffering from the placebo effect. Possible, but the day after I did this to my wife's 2.5i (without her knowing), she came home and asked if I had done anything to the car, because it felt faster.
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