uniberp Posted October 12, 2007 Share Posted October 12, 2007 I'm looking now for a less restrictive exhaust system for the Legato or Forester. The stock connector pipe is 2" id, which is the same size as the head ports. Seems to me a 2.5" ID Cat-back would be a better option. I know Borla makes a header for the dual port heads, but they don't make a larger cat-back. I expect the dual catalytic convertors are restriced to 2 inches for emissions purposes, so I don't know if a larger cat-back woudl benefit anyhow. In general I have found that less restriction is better overall. The old argument about backpressure being good is a myth. The parts guys checked Walker/Dynomax and the other major mfgs, and Borla and came up with nothing. Is my only choice: custom? Link to comment Share on other sites More sharing options...
Gene J Posted October 13, 2007 Share Posted October 13, 2007 A good muffler place could do this for you. When the GT needed a new exhaust I got 2 1/4 all the way back! And without a resonator it still sounds the same. Link to comment Share on other sites More sharing options...
beataru Posted October 13, 2007 Share Posted October 13, 2007 check with jegs or summit or whatever and get a high flow cat or, look for some of those SPT things or STI bolt on things, these are subarus, thing bolt on to eachother. The cats do restrict flow but bear in mind car makers generally do make a desent exhaust nowadays (by nowadays I mean since around 1998 so....) and if you go custom, go stainless its always in every way better in the short and long run! Link to comment Share on other sites More sharing options...
destey Posted October 13, 2007 Share Posted October 13, 2007 I'm looking now for a less restrictive exhaust system for the Legato or Forester. The stock connector pipe is 2" id, which is the same size as the head ports. Seems to me a 2.5" ID Cat-back would be a better option. Does the stock pipe actually restrict? These aren't exactly high horsepower motors. Link to comment Share on other sites More sharing options...
JEGIII Posted October 14, 2007 Share Posted October 14, 2007 I used one of these on my '97 OBW. With the Borla headers and stock cat-back. Sounds good and seems to have a little more zip. Got them here; http://www.boxer4racing.com/. Link to comment Share on other sites More sharing options...
xrturbo Posted October 15, 2007 Share Posted October 15, 2007 For the header I would stay as far away from Borla as possible. I got one for free that had been welded from prev. cracks, I hung it and had to pull it down to re-weld it. And now it is finding new places to crack. I would just go with a Borla style ebay header. Un-equal is the way to go as far as sound. I first used an equal length and it sounded like a Honda. I am not sure what is out there for a cat back setup but I just gutted the rear cat and hung a Magnaflow muffler. The Magnaflow with the Un-el header sounds amazing, and there is no annoying drone on the highway. Link to comment Share on other sites More sharing options...
idosubaru Posted October 15, 2007 Share Posted October 15, 2007 some else had cracking borla headers on his EJ engine (Andyjo i believe). got multiple replacements and they all did the same thing. as for backpressure not being an issue, that's definitely not true. keeping in mind that pricinples for turbo and non turbo differ competely. speaking of non-turbo, i don't know if "backpressure" is the right terminology but i've done enough different exhausts to know for sure that too much/too big is definitely counterproductive. running larger pipe and straight pipe all the way back is not advisable, i've done that. open it up too much and you loose low end grunt significantly. just look at any actual dyno plots of an exhaust upgrade, they gain more power but at higher RPM's and shift the entire curve. depends what kind of driving you're doing. if yo'ure racing you're living in the upper RPM range and don't care about low end. but for daily driving something like a race style set up, it's annoying. feels like a lug starting off with no power, that's no fun for daily driving. you'll want to be somewhere in between. Link to comment Share on other sites More sharing options...
Virrdog Posted October 15, 2007 Share Posted October 15, 2007 At no point should a N/A exhaust get larger than a previous length of pipe. So whatever size it is at where you are replacing it, just do the same size all the way back with less restrictions. Link to comment Share on other sites More sharing options...
beataru Posted October 15, 2007 Share Posted October 15, 2007 Wow, people having problems with their borlas eh? Merkatroid has a borla on his RS and he hasnt had problems as of yet. I wonder what the deal is on those, they must have had a bad set and a good set or something like that! And yeah Equal lengths are nice for turbocharged cars when it comes to power but.... They will make the subaru sound like any other 4 cylinder out there!!! this is becoming a good thread! Im interested to see what others have done to their exhaust on the ej's! And Merkatroid (my bro in law) also has a Scoobie sport muffler on his car (You guys hopefully have heard of the great scoobie sport products if not, well then, time to learn how rad they are ) The reason I bring this up is because I belive (not exactly sure on the sizes) it goes from 3 to 2.75 and then to something else.. I just know it shrinks a little bit to help with back pressure (this scoobie sport muffler sounds great, I really really want it on my little car) anyways hope it helps!!! EDIT: I adjusted the size, it has a 3 in exhaust not 3.5 Link to comment Share on other sites More sharing options...
Virrdog Posted October 15, 2007 Share Posted October 15, 2007 The reason I bring this up is because I belive (not exactly sure on the sizes) it goes from 3.5 to 3 and then to something else.. I just know it shrinks a little bit to help with back pressure It has nothing to do with backpressure, that's just a side effect of smaller piping. Its all about the exhaust gas velocity. Link to comment Share on other sites More sharing options...
uniberp Posted October 15, 2007 Author Share Posted October 15, 2007 It has nothing to do with backpressure, that's just a side effect of smaller piping. Its all about the exhaust gas velocity. Are you saying increased turbulence within a larger pipe increases the exhaust pressure? I don't think that's true. I suppose it's possible, but the basic volume vs wall area calcs say otherwise. Link to comment Share on other sites More sharing options...
jamal Posted October 15, 2007 Share Posted October 15, 2007 no, he's saying that the important issue with exhaust piping is having it sized appropriately for the flow rate. Too small and it's restrictive, too large and the exhaust slows down and causes a loss of power/scavenging. Ideally you don't want back pressure; you want quick and efficient flow. The whole "too big and you'll lose low end power" issue isn't because of a lack of backpressure, it's because of a lack of exhaust flow in a large pipe at low revs. Exhaust sizing is the same as cam profiles and timing and intake size/runner length etc. It really only has one ideal rpm, and has to be a compromise to work across the entire range. From what I've heard the newer H6es have a butterfly valve in the exhaust just like the corvette z06. I personally am going to buy the OBX EL header (this week!), and extend an STi catback (~2.25") to work with it. Still trying to figure out exactly what to do for the cat section but I have a pretty good idea. Link to comment Share on other sites More sharing options...
xrturbo Posted October 15, 2007 Share Posted October 15, 2007 I have heard mostly that people seem to like 2.25" behind a NA 2.5 with minor mods. Just gutting my 2nd cat helped my setup both sound and power. And by the way with my setup (with the un-el, single cat, and magnaflow) it sounds soooo much better than my 00 RS that had a borla header, random tech. highflow cat and greddy cat back. Just try the magnaflow..... you won't be dissapointed!! I provides great sound and tone without getting too loud. Link to comment Share on other sites More sharing options...
agostobobby Posted September 13, 2009 Share Posted September 13, 2009 Cobb tuning they do well ! Link to comment Share on other sites More sharing options...
bratman18 Posted September 13, 2009 Share Posted September 13, 2009 Cobb tuning they do well ! You gotta take a look at the post dates Link to comment Share on other sites More sharing options...
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