Noise limits...help!

[duncan]

I'm with you on that one

[Ian (DaOne)]

i think mine may of been over the 105 db limit?

am thinking about selling the nur spec r and getting something quiter, as i really enjoyed the virgin track day, and can hopefully see my self doing it again in the future!


ian

[borgue]

but for a ported rotary engine there can be no back pressure, no silencers
just straight through as the exhaust gas temperature rises mighty quick
as soon as a restriction is added.

[Stuart]

i think mine may of been over the 105 db limit?

If you were over the limit, you would not have been allowed out. You may well have been over the limit on the driveby stuff and got lucky, but you must have passed the static test.

Good advice Ollie~
bungs can cause all sorts of issues and after experiencing some of these first hand you do realise that sometimes quieter can be good. Two things back this up in my mind. When we went to the Ring the noise testing was far more common than before. I checked the figures when Dean got pulled in and virtually every car that failed or was asked for a test was an English car Why so? Do we just like a noisier car than our European petrol flavoured brethren? I suspect it might be a bit of form over function and also that Euro laws are stricter than out own, so they are just further ahead in adapting their cars for track stuff. Second point~ I was lucky enough to go out in a very tidy, very standard E30 M3 piloted by a proper driver yesterday. The only significant mod was an exhaust made by BTB. Very expensive, very well made and very fit for purpose. Tuneful throughout the revs, well under the noise limit (93dB if I recall correctly) but so nice to listen too. It didn't feel or sound worse in any way because it was quieter and I am lead to believe that NA cars are theoretically louder than their FI cousins. Is the noise just fashion then?

[slaphead]

i think mine may of been over the 105 db limit?

If you were over the limit, you would not have been allowed out. You may well have been over the limit on the driveby stuff and got lucky, but you must have passed the static test.

Is the noise just fashion then?

Stu - not all the cars were tested - mine wasn't (for example) - I must admit I was bricking it when the chappie was walking along testing random cars in case he tested my Kaki wouldn't mind finding out what it is putting out though for future reference.

~Mark

[Fast Eddy]

Well,
The chav boys certainly like a loud exhaust, but as has been infered already you can have a nice sounding but not too loud exhaust that can flow correctly if it is well designed with high flow boxes with the correct silencing volume.
Most of us know that turbo cars need little backpressure as this is created by the exhaust turbine of the turbo so a couple or one decent size box is usually sufficient. NA cars need correct backpressure to perform properly, some engines needing more than others of course. Also exhausts that are too large bore can be a bad thing and reduce low down torque. Another thing that affects the loudness or makes an exhaust appear louder is large tailpipes as the sound waves resonate after leaving the silencer box. Those of you with loud cars and large tailpipes can put a pipe the same size as the bore of the exhaust inside your tailpipe to see if this makes enough difference to keep the scrutineers happy without resticting your power. I keep most pipe sizes from 1 3/4" right up to 4" in mild steel and stainless steel.
If anyone needs extra/larger straight through silencers to get noise down a bit without sacrificing power, i have loads of boxes in stock from "2 to 3" bore. Supply only or fitted ok :-D
Eddy

[duncan]

mine did 94 db on the static test.... but static tests are great cos there is no boost nvolved

I just think if you are into track days then then it makes it easier and one less thing to worry about if the exhaust is never going to upset anyone.

[Stuart]

I stand corrected Mark~ amazed they let anyone out but there you are. Was your Kakimoto the same style as my old one> If so you would have fortunate to get through. I will ask the circuit if we can borrow the equipment for one of our evenings.

[Ian (DaOne)]

what would be a very good flowing/power exhaust for the impreza that will be track friendly?

have got a 3" decat down pipe and blitz nur spec r system at the mo, a deep burble would be nice

[duncan]

Mine is Milltek Sport and works very well from what both Pavlo at Zen and Zak at Mocom have said and is quiet enough to not worry about noise checks too