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Exhaust dB register


Homer
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[table=head;sort=7]Exhaust model|2nd cat/decat|1st cat/decat|engine spec|Member name|dB reading idle|dB reading 4rpm

Boostlogic 4in (+2nd silencer)|4in decat|4in DP|BW 88/75 single|Steve|95.0|115.3

Motoria 3in|decat|decat|TT|brettjones|93.5|104.0

Nur Spec R|decat|decat|TT|supra_steve|85.0|102.0

RSR - Envy copy|decat|decat|TT|danhicks22|86.9|101.5

TBC - 5zigen?|decat|decat|TT|Pete_TT|97.2|108.5

Whifbitz twin box 3.5in|decat|decat|TT|jaymdee|81.2|102.0

Nur Spec RX|decat|cat|TT|Branners|69.1|85.2

HKS Ti 4in|3in decat|3in DP|T61 Single|Supramatt|88.7|105.6

Whifbitz twin box 4in|4in decat|4in DP|T74 single|JamieP|96.2|106.5

Stock|cat|decat|TT|GJD|62.6|81.4

Whifbitz single box 2.5in|cat|cat|NA|Fitz|76.4|88.0

Whifbitz single box 2.5in|cat|cat|NA|scottc998|78.8|92.5

Whifbitz single box 3.5in|3in decat|3in DP|T60-1 Single|Heckler|99.0|109.0

Boostlogic 4in|3in decat|3in DP|T67 single|Homer|96.3|121.6

Whifbitz Twin box 3in|3in decat|3in DP|BW 88/75 single|Gaz6002|84.2|90.8

 

[/table]

 

All readings taken at 50cm from the exhaust at 45 degrees right of the exit angle

Edited by Steve (see edit history)
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Lol, that was a waste of money buying the whifbitz 4" twin box, its louder than my old HKS ti thats now on supramatts car:)

 

Also the whifbitz twin box 3" is louder than the single box? maybe i should cut a box of of mine to quieten it down a bit?:D

 

Yeah, it was a bit odd, I did 4 readings on your car (that's why it took a while) as I was expecting it to be quieter. Got to admit after standing behind a lot of cars today your one did sound one of the noisier ones.

 

However, it's my understanding that new exhaust takes some time to build up some soot (or whatever it is) on the surfaces which helps quiet things down. The two identical NA's with the single box system show this, one system has been on a while, the other was fairly new and was noticably louder.

 

The two single box systems were NA's and had cats in, so probably not that comparible to the TT or single with no cats. Will bring the meter to Japfest to get some more results :)

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Lol, that was a waste of money buying the whifbitz 4" twin box, its louder than my old HKS ti thats now on supramatts car:)

 

Also the whifbitz twin box 3" is louder than the single box? maybe i should cut a box of of mine to quieten it down a bit?:D

 

Ya that seems a bit loud on idle for a twin box mate though you wonted to do more track days to !

 

 

Also thanks To Homer for sorting this nice to see the difference in the exhaust db and non seem to be track friendly lol .

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Seems to show that once both cats are out you've no chance on getting on most UK tracks.

 

With the measure 105db would meet *most* track day requirements

 

:lol: even with a 2nd silencer box added to the boost logic its still the loudest :D

 

Just added my old ones with the BL original, Wez's (really) old exhaust was pretty much the same level too, but never found out the spec. (Wez?)

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Interesting stuff. Sound testing is quite a difficult one. You've got a few variations to consider like quality of the sound tester, what revs you do the test at, if its windy, how far away and which angle from the exhaust, etc. We normally test them between 4500-5000rpm approx, and they should get quieter the higher the revs. Try testing one of them again at 5000rpm instead of 4000rpm and see what happens.

Steve L's 3" twin box system on his single turbo 3" dp/mp was tested at Oulton Park with a calibrated sound tester, 4500rpm and registered 100db in the garage which normally makes them louder. And the same exhaust on jaymdee car is 2db louder with I presume 2.5" decat pipes and stock turbo which will make it quieter.

The difference between 3" and 4" will be quite a lot, I reckon 5db difference and I'm pretty sure I guessed it would be about 106db Jamie? Only way to quieten it down further would be either another silencer in the midpipe or bigger silencers on the back.

My own car used to run a 4" with 3 silencers and that was down to 93db, I now run 3.5" with 2 smaller silencers and its now 94db.

 

Hope that helps a bit.

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