Welcome to the North American Subaru Impreza Owners Club Monday December 22, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Normally Aspirated Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 08-08-2010, 03:52 PM   #1
resident1155
Scooby Newbie
 
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:
2002 Impreza RS

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.
* Registered users of the site do not see these ads.
resident1155 is offline   Reply With Quote
Old 08-08-2010, 07:28 PM   #2
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

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
Patrick Olsen is offline   Reply With Quote
Old 08-08-2010, 08:56 PM   #3
resident1155
Scooby Newbie
 
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:
2002 Impreza RS

Default

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
resident1155 is offline   Reply With Quote
Old 08-08-2010, 09:03 PM   #4
EdHilario
Scooby Specialist
 
Member#: 137398
Join Date: Jan 2007
Chapter/Region: E. Canada
Location: Toronto
Vehicle:
2004 Impreza 2.5RS
Platinum Silver Metallic

Default

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.
EdHilario is offline   Reply With Quote
Old 08-09-2010, 12:39 AM   #5
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

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.
Patrick Olsen is offline   Reply With Quote
Old 08-09-2010, 12:54 AM   #6
bulletproof4130
Scooby Specialist
 
Member#: 173704
Join Date: Mar 2008
Chapter/Region: MAIC
Location: MD
Vehicle:
07 No Show and No
Go 2.5 N/A

Default

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.
bulletproof4130 is offline   Reply With Quote
Old 08-09-2010, 09:54 AM   #7
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

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.
Patrick Olsen is offline   Reply With Quote
Old 08-09-2010, 09:55 AM   #8
EdHilario
Scooby Specialist
 
Member#: 137398
Join Date: Jan 2007
Chapter/Region: E. Canada
Location: Toronto
Vehicle:
2004 Impreza 2.5RS
Platinum Silver Metallic

Default

It makes a significant difference. Several hundred RPMs over a long distance too. Would also help with gas mileage.
EdHilario is offline   Reply With Quote
Old 08-09-2010, 10:50 AM   #9
grafton
Scooby Specialist
 
Member#: 187936
Join Date: Aug 2008
Chapter/Region: MAIC
Location: Fairmont WV
Vehicle:
97 Legacy w/12:1CR
07 WRB STi

Default

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
grafton is offline   Reply With Quote
Old 08-09-2010, 12:51 PM   #10
resident1155
Scooby Newbie
 
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:
2002 Impreza RS

Default

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!
resident1155 is offline   Reply With Quote
Old 08-09-2010, 04:56 PM   #11
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

Can you see under your car?
Patrick Olsen is offline   Reply With Quote
Old 08-09-2010, 06:11 PM   #12
resident1155
Scooby Newbie
 
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:
2002 Impreza RS

Default

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.
resident1155 is offline   Reply With Quote
Old 08-09-2010, 07:40 PM   #13
bulletproof4130
Scooby Specialist
 
Member#: 173704
Join Date: Mar 2008
Chapter/Region: MAIC
Location: MD
Vehicle:
07 No Show and No
Go 2.5 N/A

Default

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.
bulletproof4130 is offline   Reply With Quote
Old 08-09-2010, 08:42 PM   #14
bulletproof4130
Scooby Specialist
 
Member#: 173704
Join Date: Mar 2008
Chapter/Region: MAIC
Location: MD
Vehicle:
07 No Show and No
Go 2.5 N/A

Default

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
bulletproof4130 is offline   Reply With Quote
Old 08-10-2010, 12:40 AM   #15
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

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.
Patrick Olsen is offline   Reply With Quote
Old 08-10-2010, 07:44 PM   #16
GrundleJuice
NASIOC Supporter
 
Member#: 165749
Join Date: Dec 2007
Chapter/Region: South East
Location: stupid Florida
Vehicle:
2007 No YELLING
on the bus!

Default

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.
GrundleJuice is offline   Reply With Quote
Old 08-10-2010, 09:04 PM   #17
bulletproof4130
Scooby Specialist
 
Member#: 173704
Join Date: Mar 2008
Chapter/Region: MAIC
Location: MD
Vehicle:
07 No Show and No
Go 2.5 N/A

Default

Quote:
Originally Posted by Patrick Olsen View Post
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
bulletproof4130 is offline   Reply With Quote
Old 08-11-2010, 09:42 AM   #18
GEE-OTTO
Scooby Specialist
 
Member#: 201277
Join Date: Jan 2009
Chapter/Region: MAIC
Location: Arlington VA
Vehicle:
2009 Legacy GT
OBP

Default

run a long glasspack 20+ inches I used a 40 incher once
GEE-OTTO is offline   Reply With Quote
Old 08-13-2010, 09:14 AM   #19
resident1155
Scooby Newbie
 
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:
2002 Impreza RS

Default

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.
resident1155 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
HELP me with my exhaust boostedsti06 Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 3 01-15-2007 12:50 PM
Please help me reduce my understeer! Starkiller Brakes, Steering & Suspension 28 10-24-2005 06:02 PM
FS: Fender Strat Guitar - Like New; Help me buy my exhaust! brianbot5000 North West Impreza Club Forum -- NWIC 1 02-25-2005 03:10 AM
The shop messed up, help me with my exhaust!! lowridinWRX Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 12 03-01-2004 12:31 AM
Please help me with my exhaust Cardwizz Normally Aspirated Powertrain 9 06-24-2002 05:06 PM


All times are GMT -4. The time now is 01:49 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.