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Old 01-29-2007, 12:44 AM   #1
Rockgod
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Question Ok I think I messed up somewhere

Hey Everybody clue me if you think I messed up and what I should do now?

I got my Borla Headers installed on my car awhile back (Thanks go out to Rougeben83 for the advice and soundfile.) and a Flowmaster Delta 40 Series muffler. Now, I when I got the headers I didn't change the cats at first nor the muffler but my 01 BE ran fine and sounded ok. Over sometime the cats failed (to which I don't know why but that is a moot point now.) and I had to get a High-flow cat which if I remember correctly alot of guys here told me to do. Anyway, after I got the cat and the muffler I noticed a drop in low-end torque (which was told to me also. which by now I'm laughing at myself for not following the recipe for success.) Anyhow I didn't do the work myself but rather took it to my local muffler shop. My subie is the first one they've ever worked on (according to them) and I think they put the wrong size pipes after the headers. What should be the correct size for the down pipe and on? Is 3 inches too big before the H-F Cat?

I'm not a very good DIYer. So all input on this is valuable to me for now and in the future. I raise up this issue because the part I refer to in messing up is that I explained to them what I wanted but didn't clarify it. At high rpm's it sounds sweet if not a little too loud also. At low rpm's there's the loss of power and a long droning sound. Raise your hand if you've gone through this.

I've been trying to get a video file of it but I just have a camera phone so bear with me.
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Old 01-29-2007, 01:01 AM   #2
that one legacy
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edit: didn't notice that you were talking about the piping before the cat.

i think what you're looking for is 2.5" piping there, with 2.25" after the cat. i might be wrong about that though, 2.25" before the cat might be otimal as well.
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Old 01-29-2007, 01:53 AM   #3
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yeah, 3" is more for the turbo cars. However, you are probably experiencing your displeasure with the borlas more than anything. Maybe you could sell them and get the obx EL headers instead?!? You'd have better low-end torque from what I've read...
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Old 01-29-2007, 02:24 AM   #4
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Quote:
Originally Posted by janikphoto View Post
yeah, 3" is more for the turbo cars. However, you are probably experiencing your displeasure with the borlas more than anything. Maybe you could sell them and get the obx EL headers instead?!? You'd have better low-end torque from what I've read...
but you'll lose that wonderful boxer rumble. that's the one thing that really irritates me.
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Old 01-29-2007, 10:22 AM   #5
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Quote:
Originally Posted by Rockgod View Post
...down pipe....3 inch...

2001 Legacy L
Wintergreen
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Old 01-29-2007, 12:38 PM   #6
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3" too big, 2.25" is the usual upgrade. Up to 2.5" is ok post-cat, but it depends on your muffler too (my STi muffler w/ 2.5" is pretty good).

Not sure about the fouling of the cats w/ borlas. I have knockoff borlas, been running them for the past 6 months/5k miles w/ no issues. About half a season of rallyx and a couple of autocrosses with the setup too (lots of high-rpm use).

Only way you could kill a cat is by running rich, leaving excess/unburnt gasoline to go out of the engine and into the cats. I would check your 02 sensors as well; may have fiddled with your AF making you run rich; the borlas may have just exascerbated or indirectly caused the cats to go bad.

Oh yeah, DP is only for turbocharged cars. It's usually headers/midpipe(cat section)/catback/muffler that are the terms used when talking about the NA subbies.
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Old 01-29-2007, 01:14 PM   #7
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ok cool, I'm glad to have the responses come through. As for the cats, you could say I was running rich now that I think about it. I was using a fuel treatment known to damage cats if used in excess for which I was doing. And yes I did have to change my O2's when that occurred. Thanks for the input guys. now I know what to tell them to install on the car. I brought up (downpipe/midpipe) pipe before the cat LOL because it looked too big. It looked as big as the pipes after the cat which are 3" so I figured that was the power problem but wasn't sure.

Oh one more thing. Would anyone like to share a personal preference on spark plugs? I'm using NGK Iridium IX for my subie but do you think there is one better by NGK?
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Old 01-29-2007, 02:11 PM   #8
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NGK Copper V-powers are better for performance, but you don't need anything better than that on your N/A engine.
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Old 01-29-2007, 02:34 PM   #9
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Coppers are the suggested ones, but they do need to be replaced more often than the Iridiums.

Either one is fine IMO.
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Old 01-29-2007, 03:23 PM   #10
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Denso U-Grooves can substitute for the V-Powers in a pinch, but i wouldn't run them for too long. they always seem to foul up on me pretty quickly.
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Old 01-29-2007, 10:24 PM   #11
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You said 3" on a naturally aspirated car. That's where your torque problem lies. Its just too big of piping for torque. The exhaust gases are expanding too much in that large diameter pipe and are cooling and slowing down. At higher RPM's you don't notice this because the volume of exhaust gas you are pushing through is so much larger.

If your borla's are 2.25" you should stick with roughly that size piping all the way through. At the very least don't get smaller anywhere along the pipe or you'll negate the effects of the increased piping size. However, I wouldn't go larger than 2.5" anywhere in the system, because even at 2.5" you begin losing torque.

Having said that, your car will have less high end power with smaller piping, so you might notice this trade off if you were to switch. Alot of people experience check engine lights as a result of high flow cat's, It is a symptom of the performance exhausts, so make sure that that is not the reason for errors before you start replacing parts.

Happy motoring!
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Old 01-29-2007, 11:27 PM   #12
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I doubt he'll see any good high end gains from 3" exhaust. 2.5" is generally for the modded N/A engine that sees a lot of revving (track car, etc) and 2.25" is for the daily driver that wants to see gains in performance.
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Old 01-29-2007, 11:29 PM   #13
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Quote:
Originally Posted by Plays_With_toys View Post
You said 3" on a naturally aspirated car. That's where your torque problem lies. Its just too big of piping for torque. The exhaust gases are expanding too much in that large diameter pipe and are cooling and slowing down. At higher RPM's you don't notice this because the volume of exhaust gas you are pushing through is so much larger...
well, he could always wrap all the 3" pipe to keep the heat in. This would also keep heat away from the trans and from the floor of the car, both of which are better off without extra heat on them. I've never seen a whole exhaust system wrapped before, but I bet it would be kind of neat...
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Old 01-30-2007, 12:46 AM   #14
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3"...you could, but why would you? I wouldn't run that much header wrap in any car (hello premature rust and potential fire hazard). Stick to 2.25 or 2.5", should be ok.

I would REALLY doublecheck what size pipe the shop put in there to alleviate any confusion and potential arguing in this thread . I doubt that a shop would put a 3" pipe there to begin with; it's just extra cost and more work for them to make such a big pipe fit where a less than 2" one was before...
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Old 01-30-2007, 01:04 AM   #15
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Brilliant info guys. I'm wiser now than before on this topic and the spark plug question I had. I'm definitely going to have the pipes replaced to 2.25". As for the check engine light, I had that happen to me just the other day so now I know one more reason why it would activate. Ok Plays_With_Toys your saying that the total piping should be 2.25" all the way down to the muffler? Does that have an effect after the CAT? or are you just referring to the midpipe? My goal of course is to regain some of the power i've lost due to the change in size in the overall piping and the fact of the headers being longer than the stock ones. Also, LOL i'm not trying to lose that groovy boxer sound. Thanks to janik on the recommendation on the OBX but I love my Borlas.
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Old 01-30-2007, 01:11 AM   #16
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OBX's have it's own midpipe...you don't need to do any other work on yours are it replaces it. It doesn't have a cat though, so you may have to weld in a cat of your own choosing in place of the resonator.
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Old 01-30-2007, 01:14 AM   #17
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I'm going to Ben. But it struck me funny when the shop told me my car was the first subie they've worked on. Hondas yes. Subaru no. And that was from the owners who are father and son. Hell they loved the way it sounded when the work was done. And they mainly work on Chevys, Fords and ahem! hondas. I have a lot of honda ricers in my part of the Bronx with their freaking wrannnng.
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Old 01-30-2007, 01:32 AM   #18
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Hmm...well I know a shop in Queens that does a lot of subbies (and a lot of other modded cars), it's out by College Point. They have their own mandrel bender, which is a plus, but they can be pricey.

They did my exhaust. Very nicely done 2.5" all in one piece from the cat-back. Tucked way under the car, which I found out later on is a big plus for rallycrossing. My muffler is actually one out of their parts-bin because the stuff I brought to them wouldn't really work right.
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Old 01-30-2007, 01:37 AM   #19
Rockgod
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Location isn't a problem and I would like to know more anyway. The only thing I wish I could do is tune it more. But that doesn't seem realistic right now. Turbo is out of the question. But i'll be happy when it gets some power back.
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Old 01-30-2007, 01:44 AM   #20
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http://www.rjcustompiping.com/index.htm

There you go. When I was there, there was an 80's bi-turbo'ed 911 (wasn't sure if it was aftermarket or factory) that they were doing some exhaust work on...also saw a Civic Si get dyno'ed (~165hp at the wheels...underrated stock specs whew). Good guys, but like I said they can be a little more expensive than a typical muffler shop because they really do a lot of custom work rather than typical midas stuff.
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Old 01-30-2007, 01:51 AM   #21
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great! thanks for the info.
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Old 01-30-2007, 03:15 AM   #22
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Here's some reading to get you started. There's quite a few good articles floating around the net.

I skimmed this one because I couldn't find the one I wanted, but the info looked pretty good:

http://www.nsxprime.com/FAQ/Miscella...austtheory.htm
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Old 01-30-2007, 10:58 PM   #23
Rockgod
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P.W.T thank you very much on the website. I'm reading it now and I'm absorbing the info. The info concerning pipe diameters cements what was said here by yourself and the others. I'm going to work on a before and after of my setup to video once my vidcam comes in. I'm going to contact the shop rougeben83 recommended to me. because I want this done right. especially by a shop who has experience with subies. The first vid you should be able to notice the LOUDNESS of my car. I drove today and a guy in a WRX STi next to me asked me what I was running with. I sheepishly said "Stock" . And he looked at me like BS.
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Old 01-31-2007, 12:09 AM   #24
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Well, it's not entirely stock if you're running exhaust.
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Old 01-31-2007, 12:50 AM   #25
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Make sure you think through it all, and don't be afraid to ask questions. I've spent much more on my exhaust than if I had just done it right the first time.
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