STiSubie109 Posted June 21, 2005 Share Posted June 21, 2005 So im looking into getting a downpipe and free up some hp/tq but still use the stock exhaust. I reading up on boost creep and didnt know if this would cause it? Would i be better off getting a shorty that just reduces to one cat or go completley catless with a full dp? Any recomendations for DP? There is a big selections out there! Also...it does not seem that tuning is required but recomended to get the full gains, correct? Thanks in advance guys!! Link to comment Share on other sites More sharing options...
YBNormal07 Posted June 22, 2005 Share Posted June 22, 2005 It is possible to get boost creep with a straight through DP, but with the stock exhaust, I can't say for sure as that resonator sure looks restrictive. I do know for a fact that a dp with high flow cat on an STi will not give you boost creep, but without an HF cat can. You will need EM to take advantage of it though. Cobb AP or UTEC+tuning are two of the most popular. You don't have to get the tuning though. I have no clue what kind of numbers a leg with dp and no EM puts out. Link to comment Share on other sites More sharing options...
sutter2k Posted June 22, 2005 Share Posted June 22, 2005 it is my understanding the that the stage 2 program from cobb more effectively deals with boost creep associated with the much free-er flowing exhaust. Link to comment Share on other sites More sharing options...
Deer Killer Posted June 22, 2005 Share Posted June 22, 2005 Boost creep is a mechanical problem, programming cannot help. Link to comment Share on other sites More sharing options...
firedawgs Posted June 22, 2005 Share Posted June 22, 2005 Don't forget to get your MIL fix for the downpipe. Your choices for downpipe: Cobb $425 Lachute $495 Stromung $190 Perrin $349 Rally Performance $249 Cobb,Lachute, and Perrin are full length downpipe (replacing both the 2nd and 3rd cat). The Stromung and RP are a "shorty" (replacing the 2nd cat only) Stromung and perrin use a seperate wastegate, whereas, cobb, lachute, RP use a bellmouth design. Lachute states the bellmouth is better against boost creep. I say it likes comparing apples and oranges. I just bought the Stromung. I used it in MY04 WRX and loved the results. Updated my vBGarage: Link to comment Share on other sites More sharing options...
liquidiq Posted June 22, 2005 Share Posted June 22, 2005 Don't forget to get your MIL fix for the downpipe. Unless you have engine management and can delete that o2 code Link to comment Share on other sites More sharing options...
scans007 Posted June 22, 2005 Share Posted June 22, 2005 PLTek is coming out with a shorty too, very very soon...... Link to comment Share on other sites More sharing options...
rockford33 Posted June 22, 2005 Share Posted June 22, 2005 Are there any dp's out there (or in development) that retain the 2nd and 3rd cats (but replace one or both with an HFC)? The long ones all seem to do away with at least one cat, as do the shorty's. I'd be interested in a full length dp with the 2nd and 3rd cat replaced with HFC units. More expensive, but also still looks legal. Just a thought. Any advantage of a shorty over a full length dp? Link to comment Share on other sites More sharing options...
Drift Monkey Posted June 22, 2005 Share Posted June 22, 2005 http://legacygt.com/forums/showthread.php?t=5643&highlight=boost+creep Link to comment Share on other sites More sharing options...
AWDxBOOST Posted June 22, 2005 Share Posted June 22, 2005 Are there any dp's out there (or in development) that retain the 2nd and 3rd cats (but replace one or both with an HFC)? The long ones all seem to do away with at least one cat, as do the shorty's. I'd be interested in a full length dp with the 2nd and 3rd cat replaced with HFC units. More expensive, but also still looks legal. Just a thought. Any advantage of a shorty over a full length dp? yes...lachute offers a dp with a hfc...cobb is making one too i believe Link to comment Share on other sites More sharing options...
scans007 Posted June 22, 2005 Share Posted June 22, 2005 Cobb has made one....and I now have the Lachute DP with HFC....=) Link to comment Share on other sites More sharing options...
rockford33 Posted June 22, 2005 Share Posted June 22, 2005 Cobb has made one....and I now have the Lachute DP with HFC....=) I thought the Cobb and Lachute units eliminated the 2nd cat? Are there any out there that don't eliminate any of the cats, but replace them with HFC's? Link to comment Share on other sites More sharing options...
AWDxBOOST Posted June 22, 2005 Share Posted June 22, 2005 I thought the Cobb and Lachute units eliminated the 2nd cat? Are there any out there that don't eliminate any of the cats, but replace them with HFC's? like we said...cobb and lachute...replace the 2 with 1 high flow unit Link to comment Share on other sites More sharing options...
STiSubie109 Posted June 22, 2005 Author Share Posted June 22, 2005 Also, will the addition of a DP reduce reliability and durability of the engine? Link to comment Share on other sites More sharing options...
Drift Monkey Posted June 22, 2005 Share Posted June 22, 2005 Also, will the addition of a DP reduce reliability and durability of the engine? no. you are doing the car a favor. Link to comment Share on other sites More sharing options...
mbacis Posted June 22, 2005 Share Posted June 22, 2005 like we said...cobb and lachute...replace the 2 with 1 high flow unit Pretty sure he's asking about a DP with two HFCs. I would be interested in this as well. There's something about going from three cats to one that I'm not crazy about, I'd prefer to have two high-flow cats in the downpipe or get a shorty with a HFC and retain the stock third cat. I realize I wouldn't be getting maximum gains, but I'd like to clean up the exhaust a little bit, try to strike a balance between performance and emissions. Link to comment Share on other sites More sharing options...
KGreb Posted June 22, 2005 Share Posted June 22, 2005 I believe Rally Performance said they could deliver something this if you bought a catted downpipe and catted center section. However, I don't know if they've actually built up the pipes they were discussing. After they couldn't be bothered to return my PMs I just went with a single cat Lachute pipe. Link to comment Share on other sites More sharing options...
YBNormal07 Posted June 23, 2005 Share Posted June 23, 2005 You can easily fab in a 2nd HF cat to a Cobb or Lachute DP with the HF cat already installed. TBH, I can't understand why, but everyone has their own thoughts and needs. Here are few "solo" HF cats that could be used: http://www.machv.com/busrachigcat.html http://shop.store.yahoo.com/hopup1/hehicatst303.html and of course...ebay: http://search.ebay.com/high-flow-cat_W0QQfkrZ1QQfnuZ1QQfromZR8 It's been my experience that as long as you have one CF cat, emissions and visual can be passed (at least in PA, chester county). Link to comment Share on other sites More sharing options...
abakja1 Posted July 4, 2005 Share Posted July 4, 2005 Since Im piecing my exhaust together, an uppipe and dp are my first choices,.. With a Perrin DP cause its cheaper,..will it bolt to stock axle back exhaust? I was thinking about getting the Stromung shorty, but figure go "big" all the way thru,..figure "might as well" go 3" all the way thru,..I have to figure in shipping costs too so I wish I could get the Lachute, but unless anyone knows of any sales or "free shipping or maybe $20 more" to Hawaii 96818,..then Id be more interested to get that,..Any downsides to Perrin DPs as we dont have our own "review" section filled up yet?? What else/fixes do I need to get rid of all cels other than resistor for upipe since I will have to wait to get a axle backtill later?? thanks Kevin Link to comment Share on other sites More sharing options...
franklin Posted July 5, 2005 Share Posted July 5, 2005 Are there any dp's out there (or in development) that retain the 2nd and 3rd cats (but replace one or both with an HFC)? The long ones all seem to do away with at least one cat, as do the shorty's. I'd be interested in a full length dp with the 2nd and 3rd cat replaced with HFC units. More expensive, but also still looks legal. Just a thought. Any advantage of a shorty over a full length dp? My take on the advantages of the "shorty d/p" is A) this is the major restriction in the exhaust system B) a shorty will leave the stock 3rd cat in place and w/o a close exam look "more" stock C) its about $250 vrs $450-600 for a full catted d/p. As to a full d/p with 2 cats dont know of any made. The full d/p's w/ cats all replace the 2nd and 3rd cats with 1 high flow cat. NOTE: if you leave the stock uppie alone it still has a cat. Franklin Link to comment Share on other sites More sharing options...
franklin Posted July 5, 2005 Share Posted July 5, 2005 Another fact until 50,000 miles or if destroyed you cant legally replace the cats anyway. So even if you put 2 high flow cats in place of the 2nd and 3rd cats its still illegal. Link to comment Share on other sites More sharing options...
zildjiank Posted July 5, 2005 Share Posted July 5, 2005 Aright, great, so now that we know we are going to be illegal in anything we do w/ the car....I just want to know, when I go to smog it (and how often does that have to be done?), I just put on the stock stuff right? B/C it's all bolt on right? THEN will all be good? Link to comment Share on other sites More sharing options...
jaymesbry Posted July 5, 2005 Share Posted July 5, 2005 you dont have to smog our cars for like 5 years later. And yes, all you have to do is put the stock stuff back on and you will be ok. now putting that stuff on.. is a pain Link to comment Share on other sites More sharing options...
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