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08-08-2010, 02:52 PM | #1 |
Scooby Newbie
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:2002 Impreza RS |
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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08-08-2010, 06:28 PM | #2 | |
Scooby Guru
Member#: 120
Join Date: Jul 1999
Chapter/Region:
AKIC
Location: Where the Navy sends me...
Vehicle:1997 Legacy 2.5GT 1996 Impreza coupe |
Quote:
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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08-08-2010, 07:56 PM | #3 |
Scooby Newbie
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:2002 Impreza RS |
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 |
08-08-2010, 08:03 PM | #4 |
Scooby Guru
Member#: 137398
Join Date: Jan 2007
Chapter/Region:
E. Canada
Location: Toronto
Vehicle:2004 Impreza |
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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08-08-2010, 11:39 PM | #5 |
Scooby Guru
Member#: 120
Join Date: Jul 1999
Chapter/Region:
AKIC
Location: Where the Navy sends me...
Vehicle:1997 Legacy 2.5GT 1996 Impreza coupe |
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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08-08-2010, 11:54 PM | #6 |
Scooby Specialist
Member#: 173704
Join Date: Mar 2008
Chapter/Region:
MAIC
Location: MD
Vehicle:07 No Show and No Go 2.5 N/A |
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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08-09-2010, 08:54 AM | #7 |
Scooby Guru
Member#: 120
Join Date: Jul 1999
Chapter/Region:
AKIC
Location: Where the Navy sends me...
Vehicle:1997 Legacy 2.5GT 1996 Impreza coupe |
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. |
08-09-2010, 08:55 AM | #8 |
Scooby Guru
Member#: 137398
Join Date: Jan 2007
Chapter/Region:
E. Canada
Location: Toronto
Vehicle:2004 Impreza |
It makes a significant difference. Several hundred RPMs over a long distance too. Would also help with gas mileage.
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08-09-2010, 09:50 AM | #9 | |
Scooby Specialist
Member#: 187936
Join Date: Aug 2008
Chapter/Region:
MAIC
Location: Fairmont WV
Vehicle:19 WRX & WRX STi |
Quote:
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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08-09-2010, 11:51 AM | #10 | |
Scooby Newbie
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:2002 Impreza RS |
Quote:
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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08-09-2010, 03:56 PM | #11 |
Scooby Guru
Member#: 120
Join Date: Jul 1999
Chapter/Region:
AKIC
Location: Where the Navy sends me...
Vehicle:1997 Legacy 2.5GT 1996 Impreza coupe |
Can you see under your car?
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08-09-2010, 05:11 PM | #12 |
Scooby Newbie
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:2002 Impreza RS |
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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08-09-2010, 06:40 PM | #13 |
Scooby Specialist
Member#: 173704
Join Date: Mar 2008
Chapter/Region:
MAIC
Location: MD
Vehicle:07 No Show and No Go 2.5 N/A |
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. |
08-09-2010, 07:42 PM | #14 |
Scooby Specialist
Member#: 173704
Join Date: Mar 2008
Chapter/Region:
MAIC
Location: MD
Vehicle:07 No Show and No Go 2.5 N/A |
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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08-09-2010, 11:40 PM | #15 |
Scooby Guru
Member#: 120
Join Date: Jul 1999
Chapter/Region:
AKIC
Location: Where the Navy sends me...
Vehicle:1997 Legacy 2.5GT 1996 Impreza coupe |
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08-10-2010, 06:44 PM | #16 | |
Scooby Specialist
Member#: 165749
Join Date: Dec 2007
Location: Detroit, MF'er!
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Quote:
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08-10-2010, 08:04 PM | #17 |
Scooby Specialist
Member#: 173704
Join Date: Mar 2008
Chapter/Region:
MAIC
Location: MD
Vehicle:07 No Show and No Go 2.5 N/A |
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08-11-2010, 08:42 AM | #18 |
Scooby Specialist
Member#: 201277
Join Date: Jan 2009
Chapter/Region:
MAIC
Location: Northern VA
Vehicle:2008 08 QSM 5MT LGT QSM |
run a long glasspack 20+ inches I used a 40 incher once
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08-13-2010, 08:14 AM | #19 |
Scooby Newbie
Member#: 92659
Join Date: Aug 2005
Location: Chicago
Vehicle:2002 Impreza RS |
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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