H&S exhaust @ Bedford Autodrome?

F

funkdude

Member
 London
Hi there fellows,

"The noise limits at Bedford Autodrome will remain unchanged at 101dB(A) static (measured 0.5m from the exhaust at a 45’ angle at ¾ maximum revs) and 87.5 dB(A) drive-by at 20 metres." :!:

May I ask if anyone have a standard H&S cat back fitted on their M who has experience with Bedford Autodrome? I am going to their trackday in March and I am not sure if I will pass their noise test. Dont have a dBA metre myself so I will need to rely on your advice.

When I collected my car Ian from H&S told me the noise level was 97dBA at 4,500rpm... but that figure cannot be applied to Bedford since 4,500rpm isnt exactly 3/4 max revs.

Thank you very much!
 
There's only three ways to know for sure:
1) buy yourself a cheap sound meter from Maplins - http://www.maplin.co.uk/Module.aspx?ModuleNo=226470&&source=14&doy=2m3 - and hold the revs at 5500rpm (that's where I needed to hold them at Oulton)
2) hire a sound meter from Bookatrack - http://bookatrack.com/-pp_Track-Day-Products?17
3) go to a local track during a track day and ask them to test it
 
That is true.. but I thought my exhaust really is quite loud. tbh it is a little louder than I'd like. I have already paid for the trackday so I just need to hope for the best now!

Andy reckon's his is on border line with track day regulations so mine should be okay in theory. But it all depends how strict they really are as I have heard of cars being black flagged for being 0.2dB(A) over!

Better be safe than sorry
 
Does anyone know what a standard reading is? I've ssen a guy get turned away from Croft in a standard 911 so I'm hoping for the best in the zed!
 
ive done bedford but i cant remember what my reading was...dont remember thinking it was mega close tho.
 
I did Bedford (though mine is also stock). They asked me what my redline was and then said rev to 3/4, not 4500RPM. It passed fine, ninety something IIRC but guessing...a few 911s were running with some kind of baffles on their exhausts, so that might be an option if it is slightly over.

Isn't 100Db ten times louder than 90Db? 0.2Db isn't a small as it sounds
 
Yeah its worked out by some kind of algorithm. I've had a car that was 105db static and that was pretty loud! Had to get a silencer made up before I went to Nurburgring put it that way.
 
a Z4M will go up to about 11,000rpm (red line)

3/4 rev would therefore be about 8,250rpm

My exhaust reading is 97dBA at 4,500rpm... You reckon it will exceed the limit of 101dBA at 3/4 rev? Got 4dBA of leverage...

Thing is, the car has a rev limitor of 6,000rpm at static. The rev indicator will keep bouncing at circa 5,800 - 6,000rpm if you try to max rev at static.

:( Its all a bit confusing.
 
I've never been noise tested at the 'Ring? Just drive up, put ticket in, floor it! or do you mean the GP Circuit

funkdude said:
a Z4M will go up to about 11,000rpm (red line)

Thing is, the car has a rev limitor of 6,000rpm at static. The rev indicator will keep bouncing at circa 5,800 - 6,000rpm if you try to max rev at static.

:( Its all a bit confusing.
Click to expand...

??? My revcounter goes to 9000RPM. Definitely didn't have to bounce it off the limiter! So must have been about 5.5k-6k
 
funkdude said:
a Z4M will go up to about 11,000rpm (red line)

3/4 rev would therefore be about 8,250rpm

My exhaust reading is 97dBA at 4,500rpm... You reckon it will exceed the limit of 101dBA at 3/4 rev? Got 4dBA of leverage...

Thing is, the car has a rev limitor of 6,000rpm at static. The rev indicator will keep bouncing at circa 5,800 - 6,000rpm if you try to max rev at static.

:( Its all a bit confusing.
Click to expand...

The red line is at 8,000rpm on mine (although the gauge goes to 9,000) - therefore 3/4 is 6000rpm, however I was told by the scrutineer to hold it at 5500rpm. I tried, but you need so little throttle input anyway that it was blipping between 5500 and 6000 all the time, with some nice pops on overrun - still passed though.

I'm trying to find out if they've kept a record of the reading at Oulton Park.

BTW, most circuits measure in dB(a) which is slightly different to dB - same logarithmic scale, but slightly different results due to weightings used. Something to do with whether it's sound pressure that's creating the measurement, or acoustic noise, or...I gave up listening to my colleague after that (he's a sound engineer for Cambridge Audio).
 
I do still come on here from time to time! Trouble is that because I'm not here everyday, it makes it hard to keep up with all the topics...

I did Bedford though, with my "custom" H&S (which I believe is slightly louder than the H&S sold "off the shelf"), and passed the noise regs fine :)


Oh and as an aside, DavidCH, H&R springs I'll get to you hopefully next week!
 
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