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Old 12-07-2004, 02:09 PM   #1
Unabomber
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OMGHi2U Exhaust dB data

In an effort to dispel some of the myths and confusion with regard to which exhaust is quiet or loud, I have come up with some comparative data for NASIOC users. This may help indivduals who live in remote areas or areas where few different exhausts are located to determine which exhaust is right for them.

Testing policy:
a. All measurement are and will be taken with an Exetech digital dB meter with an accuracy of plus or minus 2db using the same settings at the same distance.
b. All idle measurements are taken at warm idle, NOT cold (higher RPM) idle, and then 3000RPM.
c. All measurements are taken 6" from the tailpipe.
d. All measurements are averaged, not peak high or peak low as the exhaust dB can vary 5-10dB due to the boxer motor characteristics.

Today I measured a 100% stock 2002 WRX to "zero" my meter with the previous testing results of Turbo & High Tech Performance Magazine's data. Their data has been used as well to broaden the information as they tested some unique exhausts.

With every Subaru Meet I go to, I will bring the dB meter with me and do testing. I will bump this thread with each addition.

I won't post the results here as the bulletin board's software screws up all the cool formating, but you can download it from my server via these two links:

.xls file (MS Excel format) 31 kB

.txt file (the format will be messed up slightly) 8 kB

Exhausts tested so far:

5Zigen
A'PEXi
APS 3" & 3.5"
B&B
Blitz
Borla (XR-1 and Hush)
Bosal
Brullen
CES
Cobb Tuning
Espelir
Fujisobo
Greddy (EVO and SP2)
Helix
Heyward and Scott
HKS (Hi-Power and Carbon Ti)
Invidia
JIC
MRT
M2 Performance
Prodrive
RSR
Skunk2
SPT
Stromung (single and dual tip)
Supersprint
Tanabe
Tenso R
Thermal Research & Development
Tom Motorsports
Trust
TurboXS (Magnaflow & RFL)
Worx Tuning
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Last edited by Unabomber; 08-29-2005 at 09:37 PM.
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Old 12-07-2004, 02:14 PM   #2
Quack
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sounds good, but would 3ft be a better distance to measure?
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Old 12-07-2004, 02:15 PM   #3
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Sounds like a good test.




my next liscence plate is going to own *snickers*
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Old 12-07-2004, 02:17 PM   #4
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3ft did not jive with the testing that Turbo Magazine did to get the same readings. I am also going to look up (help anyone?) the new California dB law and find out how they are supposed to take their readings and hopefully incorporate that as well. But remember folks.....this is for fun, so don't use my findings in court!
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Old 12-07-2004, 02:18 PM   #5
Quack
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i believe that CA tests from 3ft (forgot where i read this)

Last edited by Quack; 12-07-2004 at 02:31 PM.
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Old 12-07-2004, 02:27 PM   #6
Quack
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jsut found this:
http://www.dmv.ca.gov/pubs/vctop/vc/vctoc.htm

27200. (a) The Department of Motor Vehicles shall not register on a dealer's report of sale a new motor vehicle, except an off-highway motor vehicle subject to identification as provided in Division 16.5 (commencing with Section 38000), which produces a maximum noise exceeding the applicable noise limit at a distance of 50 feet from the centerline of travel under test procedures established by the Department of the California Highway Patrol.

Limits for Vehicles under 6000 GVWR

27206. For the purposes of Section 27200, the following noise limits shall apply to any other motor vehicle, not specified in this article, manufactured:

(1) After 1967, and before 1973 86 dbA
(2) After 1972, and before 1975 84 dbA
(3) After 1974 80 dbA

Limits for Vehicles Exceeding 5,999 Pounds Gross Vehicle Weight

27204. For the purposes of Section 27200, the following noise limits shall apply to any motor vehicle within the specified manufacturer's gross vehicle weight rating and date of manufacture:

GVWR-Pounds Date of Manufacture Noise Limit -dbA
Over 6,000 after 1967 and before 1973 88 dbA
Over 6,000 after 1972 and before 1975 86 dbA
Over 6,000 after 1974 and before 1978 83 dbA
Over 8,500 after 1977 and before 1982 83 dbA
Over 6,000 but not over 8,500 after 1977 80 dbA
Over 8,500 but not over 10,000 after 1981 80 dbA
Over 10,000 after 1981 and before 1988 83 dbA
Over 10,000 after 1987 80 dbA
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Old 12-07-2004, 02:37 PM   #7
Vikingmoose
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Unabomber-

I posted a SPL comparison of a stock vs. Prodrive ovaltip axle back a while ago in the Car Parts Review forum (I think). It is a complete and thorough test including ambient, stock and Prodrive levels all broken down into octaves (although not necessary). If you search, I'm sure you could find it, and of course, the info is all yours for the taking!

-Justin (aka: vikingmoose)
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Old 12-07-2004, 02:38 PM   #8
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Society of Automotive Engineers (SAE) test procedure J1169 (May, 1998) is how it is to be tested.

it turns out to be 95db @ 20" (see page 4)
http://www.ci.kennewick.wa.us/City_Clerk/KMC/11-36.pdf
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Old 12-07-2004, 08:51 PM   #9
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My first update!

Thanks for the offer Justin, but I tested the Prodrive oval tip tonight on my car.

Thanks for the update on California testing. I'm still not 100% sure if I can/should include this "California data" into my tests or not. I'm pretty sure some asshat will sandblast me down the road if they buy an exhaust and I post that it's "legal" and they get a ticket when this testing is 100% NOT official. If any of you think I should please PM me or post with your thoughts and I'll consider it.
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Old 12-07-2004, 09:41 PM   #10
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Quote:
Originally Posted by Unabomber
My first update!

Thanks for the offer Justin, but I tested the Prodrive oval tip tonight on my car.

Thanks for the update on California testing. I'm still not 100% sure if I can/should include this "California data" into my tests or not. I'm pretty sure some asshat will sandblast me down the road if they buy an exhaust and I post that it's "legal" and they get a ticket when this testing is 100% NOT official. If any of you think I should please PM me or post with your thoughts and I'll consider it.
I think you should take measurements at the distances and angles specified by CA regs (which, so far, have not been presented here).
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Old 12-07-2004, 09:52 PM   #11
banzai
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thanks for the test today ron! now we know who is the loudest!!
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Old 12-07-2004, 09:54 PM   #12
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What surprised me is on the Greddy Evo, is that it actually got quieter at 3000rpms just like they claim. Infact other than stock it was the most quiet system on their. Good info Unabomber!! (thumbs up)
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Old 12-07-2004, 09:54 PM   #13
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Quote:
Originally Posted by Jon [in CT]
I think you should take measurements at the distances and angles specified by CA regs (which, so far, have not been presented here).
Throw a brother a bone here Jon! You are the .pdf/regulation Guru, hook a brother up if you know/can find the real info!

From my limited research, I would need a sound level meter complying with ANS S1.4-1971 (mine isn't and the real things run ~$300) and would have to comply with SAEJ1169 Testing Procedures:



And the Engine RPM must be held steady at 75% of rated peak horsepower RPM. Given the latter figure is 6,000 RPM for the US spec WRX/STI, the test speed is 4,500 RPM for these vehicles.

This is all too much of a pain for me to think of doing, so sorry California Scooby owners.

Last edited by Unabomber; 12-07-2004 at 10:55 PM.
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Old 12-07-2004, 09:54 PM   #14
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yeah, i remember hearing in a couple different db tests about the meter being held at 45 degrees to the tip of the exhaust.
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Old 12-08-2004, 03:50 AM   #15
tribalwrx
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good intel unabomber but damn i didn't think my helix setup was 110db loud at 4000rpm's


mike
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Old 12-08-2004, 04:03 AM   #16
MB38
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Thanks, Unabomber. This is why you're the master.
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Old 12-08-2004, 04:42 AM   #17
elhalisf
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Petition to change "FAQ Master" to "Master to all that is NASIOC.COM" but that probably wont fit so "NASIOC Master"

Anyhow back to the point, ever tested a Spugen Catback. I got it on mine and I have to say at idle this thing is AMAZINGLY quiet. When I met up a few guys around here when I was parting out my car, ALL of them said that they never even heard my car comming. One person even thought my car was off until I poped the hood. But once you go full WOT this thing sounds so damn free flowing its UNBELIEVABLE. I might just have to buy the testing unit and do some testing for you guys.

What is the name of the testing unit?
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Old 12-08-2004, 05:04 AM   #18
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Damn, no decibel test of the stromung exhaust. Anyone have a decibel meter in Socal? My

Here is a video I took of the other day if anyone wanted a video of what the stromung exhaust sounds like. http://boxware.cx/~fileid/WRX/stromung.wmv

I'm thinking of picking up digital decibel meter from radio shack but I can't justify the cost of $50 for one reading.
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Old 12-08-2004, 05:16 AM   #19
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Quote:
Originally Posted by file_id
Damn, no decibel test of the stromung exhaust. Anyone have a decibel meter in Socal? My

Here is a video I took of the other day if anyone wanted a video of what the stromung exhaust sounds like. http://boxware.cx/~fileid/WRX/stromung.wmv

I'm thinking of picking up digital decibel meter from radio shack but I can't justify the cost of $50 for one reading.
Can you justify using the return policy? I can
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Old 12-08-2004, 05:19 AM   #20
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But that would be immoral and unjust.
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Old 12-08-2004, 06:21 AM   #21
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Quote:
Originally Posted by file_id
Damn, no decibel test of the stromung exhaust. Anyone have a decibel meter in Socal?
Not to fear....Stromung testing will occur this Sunday. Plus, I will be in Socal (San Diego) in March going to a school for 4 months. Hopefully I can test a bunch of people up in LA during my "Unabomber invades Socal tour".

Last edited by Unabomber; 12-08-2004 at 07:22 AM.
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Old 12-08-2004, 10:06 AM   #22
mbiker97
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You have way too much time on your hands Ron!

This should be really interesting though.
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Old 12-08-2004, 10:36 AM   #23
WRXBlue02
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After looking at the chart I never expected my exhuast to be so loud
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Old 12-12-2004, 11:07 PM   #24
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Bump for the update! I tested 25 exhaust combos at a local meet today. Testing sucks when I should be hanging out with locals. One local did own me and my meter with his RICH exhaust by spraying a gas/carbon mixture all over my meter and my pants.
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Old 12-12-2004, 11:18 PM   #25
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Thanks for helping the community Ron.
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