Exhaust dB noise levels

[BruceLee911]

Hi,

I was trying to find out default dB levels for a 996 exhaust? Without getting it tested at a garage I wondered if anyone knew what it roughly is? I have a track day soon and have found out the day has a limit of 98dB and not 105dB as advertised. I was thinking of trying an Iphone app, but don't know if this will be sensitive enough or calibrated correctly. My C4S has sports exhaust fitted but obviously this could be switched off (disgusting thought I know) if required to lower the level. If it exceeds the 98 - I can't go on the track!

 

[stevett]

I went to a recent track day at Brands and C4 with standard exhausts is 98db at 3/4 revs - approx 5000rpm according to the official scrutineer.

You should be okay.

Steve

 

[watlina]

I've also got a PSE (with no switch so permanently loud []) and was concerned about the noise at one of the Porsche Silverstone Experience days (in the end they don't care)

I got the safety man at work to come out to the car park one dinner time with his calibrated dB meter to check. We followed what seems to be the standard test regime of :-

ISO 5130:2007 Acoustics "” Measurements of sound pressure level emitted by stationary road vehicles
http://www.unece.org/trans/doc/2007/wp29grb/ECE-TRANS-WP29-GRB-45-inf01e.pdf

Most of the trackday setups appear to do it this way.
http://javelintrackdays.co.uk/jt/index.php?option=com_content&task=view&id=5&Itemid=22
http://www.clubmsv.com/car-trackday-noise-limits.aspx

It appears to be rather load. At a constant 5400rpm it was 108dB and if I blip it to the red line it would peak at 115dB. To me it sounds excellent ;-) but I guess I wouldn't get on many trackdays.

With it set to quite mode I'm sure you'd have no touble passing the test.

 

[Richard_Hamilton]

That's interesting. Mine won't rev above about 3500 (IIRC) in neutral. After that, it cuts the igniton and fluctuates around 3500. I wondered if there was something wrong, so I tried it on another 996T Tip, and it was the same.

 

[Richard_Hamilton]

Just another thought - it would be fairly simple to connect up a pipe and tee piece between the inlet manifold and the actuating valves, so that it runs quiet for track days.

 

[BruceLee911]

My C4S seemed not to want to rev higher than around 3.5K in neutral... as it happened the guy doing the DB test at Brands was actually not too bothered on the day when I mentioned that SPE and after a few seconds of me revving the engine he stuck the pass sticker on the screen and that was that, but didn't actually tell me what the level was. Only one guy I spoke to who was driving a Noble (Ford engine from a Mondeo with twin turbos) was slightly over the 98dB and the chap just told him to take it easy.