Greddy Power Extreme 2 Epa 'ed At 93db(a)

[immortal^]

Hi all,

Just a quick question, I recently bought a 3" greddy power extreme II cat back exhaust system with a 3" front pipe, the thing looks great and really isn't that loud (if compared to whats around) but has a nice grunty sound when you accelerate(not a droning noise), Now I thought I would be Pro active and go to an exhaust outlet that is a EPA approved noise tester and get a noise test done to my exhaust at EPA standards, just to see how I would fair, to my dismay the exhaust had a sound pressure reading of 93db(a) (90db being the legal limit), just 3db over the limit !!

Question: Is there anything that can be done to easy that sound pressure down a little?? any tricks of the trade?? can the exhaust be wrapped to help deaden the noise ? or is there anything else that might help drop the sound pressure down just a fraction? please help ....

PS Please dont post stupid obvious responses like, put your stock exhaust back on, or you will get a public for your troubles...

Thanks all.

Edited October 18, 2007 by immortal^

[bloodsword27]

ok this might sound stupid (and i wouldnt recommend for street) but my freind put some steel wool in the zorst to clear EPA...basically took ALL the sound out (and probs kept all the exhaust gases in)....a silencer will do the job easily

[Jmaac]

I wouldnt worry about it that close, theres usually a tolerance allowed for machines such as these i.e. as a result of other noise interferance, position when taken (wave patterns/nodes cancelling in/out), plus more. I would say +/-5% easy which would make your exhaust comply with EPA

Otherwise, stick some steel wool in there, it will deaden the sound enough to pass a epa test and will burn out after about a week. Doesnt harm exhaust at all..... o/wise goto motorbike shop and get internal fibreglass baffle to suit 2 stroke muffler and stuff that in there (you'll have to dig that out cos it wont burn like s/wool)

Unfortunately if you wrap the exhaust you'll just force more noise out the back straight into the device (it will make it quieter in the car for you) only way to quieten it is improving the internal baffle (increases turbulence) hence above.

Alternatively you may be able to buy/fabricate a restrictor for your muffler. These fit into the tip and increase backpressure at the outlet causing the sound to bounce back into the muffler, in turn cancelling some frequencies and disapating more noise through the baffle

all these methods will increase your backpressure obviously and decrease your peformance at high rpm.

[Ronin 09]

i'm confused mate, if you haven't been reported to the EPA then don't worry until you do.

if it isn't too loud (doesn't sound like it is) then you probably shouldn't be reported to the EPA.

cheers

[STATUS]

fit a restrictor in between pipe one and two. Tkes less than 2 mins to remove and replace.

think normal gasket but with a 2" hole instead of a 3" hole... works a treat for epa noise testing

[R31Nismoid]

I wouldnt worry about it that close, theres usually a tolerance allowed for machines such as these i.e. as a result of other noise interferance, position when taken (wave patterns/nodes cancelling in/out), plus more. I would say +/-5% easy which would make your exhaust comply with EPA

Well your wrong there unfortunately.

93 is 93. There is no "variance" allowance. Never has been.

So moving on, you probably need to look at changing a muffler to a better one.

3db is reasonably easy to knock out and keep it flowing.

Hell my 3.5" made 93db aswell, so easy to get it a bit quieter with a better muffler or whatever.

You can weld in restrictors, but thats a pin in the ass each time. Although with 93db its highly likely that you wont be pinned.

I wouldnt worry till you get the letter in the mail as 93db is much quieter than the usual 100+ systems that most people have.

[skylinecouple]

Just put a hot dog on it. Guaranteed to knock 5db off it. So simple.

[R31Nismoid]

A guarantee you rekon? I dont think so.

I know a number of people who have installed hot-dogs thinking it would work... and in the end had little-to-no impact to the overall db, the 'drone' is affected more than the outright noise based on what ive seen

[Green_s13]

yup a hot dog did nothing for me, the only thing that reduced the noise is my car was changing the rear muffler, as said though i wouldn't worry about it until you done for it

[immortal^]

Cool, Some good suggestions, thanks for the feedback guys

[GTST98]

to get mine passed i made up a reducer in the back of the cannon , it slipped in side the tip had one little rivet up from the bottom to make sure it didnt come out during rego check , in steed of a 5 inch hole in the cannon it was like 3.5inch or something didnt look stupid , used another piece of ss pipe to go down the canno bout 3 inchs and then a bit of pate tig welded to the end of the 3.5 inch piece and then put it in the lathe to machine it round and bore the internal dia out. worked for me easy to take in and out , made an easy 5-10db difference that what i did any way cheers

[Adriano]

I personally wouldnt worry, 93 db is exactly twice the sound pressure of 90db. 90 db is really quiet, to got my Z32TT to 90 db i had to bolt in restrictors and heaps of steel wool, it sounded like a sewing machine, and i didnt boost it as it felt terriable, just wait for the letter, and hopefully it never will.

PS the sound test is done not under load, thats how all the "factory" V8's and the like pass, hold them at a steady 3000rpm and their quiet(thats where the test is done), give them a stab, and they bark.

[nfi]

fit a restrictor in between pipe one and two. Tkes less than 2 mins to remove and replace.

think normal gasket but with a 2" hole instead of a 3" hole... works a treat for epa noise testing

+1

Really easy 5 minute fix to make the problem "go away" why its getting tested. I would only muck around with mufflers if it was annoyly loud. 93db isn't very loud at all.

[mesmerized]

i got a 'hi-tech mufflers' resonator welded on. dropped db from 92-84db, no drone or noticeable performance loss