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Old 08-08-2010, 02:52 PM   #1
resident1155
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Default HELP me reduce my exhaust noise!

So I've had an OBX full catback on my 2002 2.5RS now for about 5 years. It's a nice exhaust, still very minimal rust. The problem is the LOW DRONE. I absolutely can't stand it, especially at cruising speed (70mph+) on the highway. I literally have to turn my radio up significantly at that speed to hear anything.

My question is, what can I do to rectify this problem? I really don't want to blow $500 on a new exhaust system when this one works fine. I was thinking I could swap out the mid-pipe for a resonated pipe, but I have a feeling the axle-back portion of the exhaust is also greatly contributing to the noise.

Anybody have any experience with these OBX exhausts? I really want to achieve NEAR stock sound if possible. I went to Midas recently and they said they cant put a glasspack or resonator in because there's not enough room.

Any help is appreciated! Thanks.
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Old 08-08-2010, 06:28 PM   #2
Patrick Olsen
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Quote:
Originally Posted by resident1155 View Post
I was thinking I could swap out the mid-pipe for a resonated pipe...

I went to Midas recently and they said they cant put a glasspack or resonator in because there's not enough room.
This statement confuses me. Based on the first sentence, you have a mid-pipe with no resonator now, right? So what additional room does Midas need to add a resonator?

My exhaust was getting a little drony, plus the cat/mid-pipe section was a bastardized combination of OBX and MRT bits, so I went to the local Midas or Meineke and told them to make me a new mid-pipe and put a bigger resonator on. They did. Maybe you just need to try a different shop and/or explain things to them better?

Oh, and I think adding a resonator to your mid-pipe would be a smart first step, and probably the most cost-effective. If it's still too loud/drony, then see about changing out the muffler section.

Pat Olsen
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Old 08-08-2010, 07:56 PM   #3
resident1155
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Thanks for the reply Pat. To be honest, I don't really remember if the OBX mid-pipe had a resonator or if it was just hollowed out. I was hoping somebody on this board might know/remember. Maybe like you are saying, I can just have the exhaust shop swap one out for a larger one. I think you are right, I can definitely KILL the drone by throwing on a bigger resonator.

In any event, I was able to cut down on noise by about 30-40% by removing the Cobb intake. That thing was absolutely ridiculous. Probably the worst investment I ever made on that car. It made the car have a lumpy idle and the shifts (4EAT tranny) were wretched, especially in the winter.

BTW, that's a very interesting pic of your exhaust...I'm curious to know are those the stock cats? My heat shields are making a TON of noise right now, I really need to rip them off soon...or just get a high performance cat
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Old 08-08-2010, 08:03 PM   #4
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It's also due to having a 4EAT. If only there was another gear. Highway speeds + exhaust + 4EAT will be louder than a 5-spd.
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Old 08-08-2010, 11:39 PM   #5
Patrick Olsen
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Quote:
Originally Posted by resident1155 View Post
BTW, that's a very interesting pic of your exhaust...I'm curious to know are those the stock cats?
The first "cat" is actually a little (probably worthless) resonator that comes with the OBX equal length header. The second cat is actually a cat - it's a universal metallic substrate hi-flow cat that I picked up somewhere. Then after that is the remains of the MRT mid-pipe (the metallic flex joint and the resonator). Now the OBX fake cat is gone, as are the two extra flanges in the middle of everything.
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Old 08-08-2010, 11:54 PM   #6
bulletproof4130
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Quote:
Originally Posted by EdHilario View Post
It's also due to having a 4EAT. If only there was another gear. Highway speeds + exhaust + 4EAT will be louder than a 5-spd.
Im curious as to what the rpms are 4EAT vs 5 spd. I doubt they are much different, but it would be nice to know. The gearing is alot higher in the 4EAT, but someone post up their 5 spd RPMs at 60, 65, then 70 and Ill get the 4EATs tomorrow.
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Old 08-09-2010, 08:54 AM   #7
Patrick Olsen
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Manual: 1st 3.454, 2nd 2.062, 3rd 1.448, 4th 1.088, 5th .780. Final 3.9
Automatic: 1st 2.785, 2nd 1.545, 3rd 1.000, 4th .694. Final 4.111

I believe those have been the same since 2006. Those are just the N/A ratios - the turbo cars have different 5MT ratios.
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Old 08-09-2010, 08:55 AM   #8
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It makes a significant difference. Several hundred RPMs over a long distance too. Would also help with gas mileage.
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Old 08-09-2010, 09:50 AM   #9
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Quote:
Originally Posted by EdHilario View Post
It makes a significant difference. Several hundred RPMs over a long distance too. Would also help with gas mileage.
not really that much with the mpg

my 4eat obs ~2200-2500 rpms @ 65 & 25-27mpg w/ ac, 31mpg w/o ac

my 5spd legacy ~2850 rpms @ 65 27-29mpg w/ ac, 31mpg w/o ac

the obs has an exhaust leak (@ the axle back) right now and sounds like crap
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Old 08-09-2010, 11:51 AM   #10
resident1155
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Quote:
Originally Posted by EdHilario View Post
It's also due to having a 4EAT. If only there was another gear. Highway speeds + exhaust + 4EAT will be louder than a 5-spd.
I kind of agree and disagree with you. After swapping out the cobb intake, when I get on the throttle it no longer "buzzes" like a space ship. It sounds like a normal car, except it has the low drone of the exhaust now. Certainly the 4EAT causes plenty of backfiring in b/w gears though which is always fun/funny. To put it in perspective, when I'm cruising around 70mph, my RPM is around 3300(+/- 100rpm).

I'm really looking for a solution though guys. Anybody know anything about the OBX mid-pipe? Does it have a resonator in there? Can one be installed? Thanks!
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Old 08-09-2010, 03:56 PM   #11
Patrick Olsen
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Can you see under your car?
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Old 08-09-2010, 05:11 PM   #12
resident1155
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Quote:
Originally Posted by Patrick Olsen View Post
Can you see under your car?
I can crawl under, but I don't have direct access to a lift. The mid-pipe has a bubble where there is probably a resonator, so my question is, if there is one, can it be removed and replaced with a larger one? I was hoping somebody might have had experience with the OBX mid-pipe. Thanks.
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Old 08-09-2010, 06:40 PM   #13
bulletproof4130
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60-2300 65-2500 70-2750

So there must be a significant difference in the gearing from the 02 4EAT to the 07 4EAT because 3300 and 2750 is quite a bit of difference. I would be running at or near 80 for my RPMs to be that high.
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Old 08-09-2010, 07:42 PM   #14
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On my way to the gas station to fuel up for the week I went ahead and went up to about 3300. I was at 82-83 mph. Im getting really curious about this. Pat come back and find me some answers...haha
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Old 08-09-2010, 11:40 PM   #15
Patrick Olsen
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Quote:
Originally Posted by Patrick Olsen View Post
I believe those have been the same since 2006.
Does that help? I'm sure you can find the 2002 ratios if you search online.
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Old 08-10-2010, 06:44 PM   #16
GrundleJuice
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Quote:
Originally Posted by resident1155 View Post
I can crawl under, but I don't have direct access to a lift. The mid-pipe has a bubble where there is probably a resonator, so my question is, if there is one, can it be removed and replaced with a larger one? I was hoping somebody might have had experience with the OBX mid-pipe. Thanks.
The OBX is steel, stainless I believe. Any aftermarket resonator can be installed as long as there is clearance with the things around it like suspension parts, driveshaft, heatshields/underbody and there is a section of straight pipe long enough to replace with it. Keep the same ID as your OBX if possible.
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Old 08-10-2010, 08:04 PM   #17
bulletproof4130
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Does that help? I'm sure you can find the 2002 ratios if you search online.
Must have missed that. So sorry I bothered you. Jesus
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Old 08-11-2010, 08:42 AM   #18
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run a long glasspack 20+ inches I used a 40 incher once
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Old 08-13-2010, 08:14 AM   #19
resident1155
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Thanks for the input guys. Can anybody recommend a good exhaust shop in the Chicagoland area? I could just go to a midas but I've had bad experiences. Thanks.
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