db levels
db levels
Author
Discussion

oli_quick

Original Poster:

380 posts

259 months

Wednesday 16th May 2007
quotequote all
Does any know what my db levels would be - about...

standard 4.5, cats still in place, sports backbox....

And how could I (if required) get this below 100db...silencers? Where and how much - can I hire them?

Thanks again

FUBAR

17,065 posts

268 months

Wednesday 16th May 2007
quotequote all
Probably in the 100-105 region imo. Tim at ACT sells track day silencers (I have a pair ) and he does, or at least used to, rent some out. Give him a phone or type

With the silencers you should be down to 95-98dba

spartacus

2,878 posts

300 months

Wednesday 16th May 2007
quotequote all
oli_quick said:
Does any know what my db levels would be - about...

standard 4.5, cats still in place, sports backbox....

And how could I (if required) get this below 100db...silencers? Where and how much - can I hire them?

Thanks again


My 4.2 with cats & quite noisy sports back box measured 104db at Brands Hatch if that helps.

carl_w

10,754 posts

288 months

Wednesday 16th May 2007
quotequote all
My 4.2 was 108 dB with cats and sports backbox (I have a noise meter). With the cats removed, it went up to 118 dB. ACT trackday silencers knocked about 8-10 dB off.

optimax sniffer

1,817 posts

245 months

Wednesday 16th May 2007
quotequote all
oli_quick said:
Does any know what my db levels would be - about...

standard 4.5, cats still in place, sports backbox....

And how could I (if required) get this below 100db...silencers? Where and how much - can I hire them?

Thanks again


Mine is the same spec. I was measuredd at Castle Combe last year at 117db, but nor confident their db meter was functioning correctly. Measured a few week ago, again at CC at 99db with track silencers. Got mine from ACT. About £120 delivered including clamps, vat etc.

byker28i

91,783 posts

247 months

Wednesday 16th May 2007
quotequote all
My 1997 4.2 with cats and sports box was 104.6db at Castle Coombe at 4K revs

I'm at Abingdon Friday with Act trackday silencers so I'll tell you then what I get

Billy_rfc

587 posts

285 months

Wednesday 16th May 2007
quotequote all
Something I've always wondered. How do that check your db level? I know that different tracks measure at different distances but is the measurement at idle or is it at a set rpm?
I've never had it done before so just curious.

Billy.

FUBAR

17,065 posts

268 months

Wednesday 16th May 2007
quotequote all
Its a bit of a mystical art akin to rolling road variences

General census of opinion is 2/3 rev range and 1 meter back, at 45 degrees. Im sure they where standing directly behind at the Ring recently, which failed a number of Cerbs.

carl_w

10,754 posts

288 months

Wednesday 16th May 2007
quotequote all
Some say 3/4 revs though. Best to err on the side of caution I reckon and get the highest reading, otherwise you may be disappointed at the track.

FUBAR

17,065 posts

268 months

Wednesday 16th May 2007
quotequote all
They told me to give it some when testing me at the Ring, so I brushed the pedal to a wholesome 1850 rpm and the tester waves me on with a smile

dempsey

297 posts

240 months

Wednesday 16th May 2007
quotequote all
I was going to buy a sound meter to try and avoid getting turned away at trackdays but the meters I looked at all had a error tolerance of 1.5 db either way which I think makes a nonsense of the track testing when +1 db can make the difference between getting through and getting turned away.

carl_w

10,754 posts

288 months

Wednesday 16th May 2007
quotequote all
dempsey said:
I was going to buy a sound meter to try and avoid getting turned away at trackdays but the meters I looked at all had a error tolerance of 1.5 db either way which I think makes a nonsense of the track testing when +1 db can make the difference between getting through and getting turned away.
I used to think that until I realized the meters used at certain track days were the exact same ones that you could get in the Maplins catalogue...

TT Tim

4,168 posts

277 months

Thursday 17th May 2007
quotequote all
FUBAR said:
Its a bit of a mystical art akin to rolling road variences

General census of opinion is 2/3 rev range and 1 meter back, at 45 degrees. Im sure they where standing directly behind at the Ring recently, which failed a number of Cerbs.


Have to dissagree with you there. The exact requirement and details of measurement are given in the MSA 'blue book' (the offical rule book of the MSA), the problem I've encountered is that the noise meters aren't calibrated, so there isn't any consistancy, I can be 102dB at one event and 106dB at another, and as the dB scale is logarythmic in progression that's a hell of a difference. All the 'blue book' states is that the meter should be calibrated regularly, but hey, every 5 years is regularly!

You are nearly correct in the details that you've given, with one small correction: 2/3 revs @ 45°, 0.5m from exhaust.

Tim

Julian64

14,325 posts

284 months

Thursday 17th May 2007
quotequote all
Can anyone categorically say mine would pass. Linked decats and standard backbox?

Anyone with same setup had theirs measured?

TT Tim

4,168 posts

277 months

Thursday 17th May 2007
quotequote all
Julian64 said:
Can anyone categorically say mine would pass. Linked decats and standard backbox?

Anyone with same setup had theirs measured?


No, do you have a dB meter Julian?

I do if you want to borrow it?

Tim

byker28i

91,783 posts

247 months

Thursday 17th May 2007
quotequote all
Castle Coombe wanted 4000 revs and measured it 0.5m away, althought their website says 4500 revs. With this I got 104.6db with cats and sports rear box.

Abingdon want 3/4 max revs at 0.5m - that's what 5500 revs? Nah I'll keep it down to 4K again I think.

TT Tim

4,168 posts

277 months

Thursday 17th May 2007
quotequote all
byker28i said:
Castle Coombe wanted 4000 revs and measured it 0.5m away, althought their website says 4500 revs. With this I got 104.6db with cats and sports rear box.

Abingdon want 3/4 max revs at 0.5m - that's what 5500 revs? Nah I'll keep it down to 4K again I think.


Yep, funny how the AJPV8 will only rev to 5500 at various venues. Mine has the same problem.

Tim