stevea
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| posted on 27/3/14 at 01:11 PM |
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BEC noise
Hi, In the next few months I intend to buy a 7 solely for track days and am quite taken by the idea of a bike engine. My question is, what sort of
static and drive by tests do BEC's produce? I know it will vary a fair bit but I think it would be a good idea to get some results from owners
to see if a BEC will work for me.
I'm up north and my local tracks; Croft, Cadwell, Elvington have fairly strict noise policies so I'd like to try and get something sub
100db static. Is this a realistic expectation?
Thanks
Steve
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raptor700
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| posted on 27/3/14 at 01:23 PM |
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I have a straight through akrapovic can 102db without the baffle in.
I have done Blyton / Cadwell and oulton all fine as they are 105db
A normal kit car exhaust will be a lot quieter.
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adithorp
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| posted on 27/3/14 at 01:26 PM |
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My car usually gets between 96-98dB static. As most of the tracks I use are normally 105 limit (Oulton, Blyton, Anglesea, Cadwell) it passes without
having to be too carefull on the revs. I've no idea what it is drive-by but I've never been pulled in for it.
Having the silencer in the Furys side pod probably helps and it's a longer than normal silencer. The exhaust broke at Blyton just after the
collector and it still didn't trip the drive-by meter, though they did hear the change in note.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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yellowcab
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| posted on 27/3/14 at 02:57 PM |
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Hayabusa engine & manifold with a standard Aprillia RSV Mille silencer is 103dB static @ 7krpm
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stevea
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| posted on 27/3/14 at 03:56 PM |
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Looking fairly good so far. I guess the option is there for me to put a bigger silencer on and deal with the slight drop in bhp.
Is induction noise the biggest problem for drive by?
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adithorp
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| posted on 27/3/14 at 04:19 PM |
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Induction noise is an issue if using an open foam filter. Some form of enclosed filter/airbox is quieter.
A bigger silencer will help. Largest diameter and length you can get away with and (if a straight through rather than baffled) shouldn't make
any significant difference to power; The exhaust tuning is compromised by the available length anyway. At least with a 7 you can go bigger; With a
Fury the side-pod limits the possible diameter.
Overall BECs get through noise testing OK but you have to avoid places with low limits, like Donnington, etc. 
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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mark chandler
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| posted on 27/3/14 at 05:15 PM |
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Induction noise killed mine at Goodwood, they are very strict, just squeezed through at Bedford.
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GreigM
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| posted on 27/3/14 at 05:45 PM |
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Under 100db will be difficult - if you are "honest" about rev limits I doubt you will pass at a 3/4 max test. After struggling at a 105db
day at Oulton when they insisted on 7500rpm for the test I bought a large silencer and still only got down to 101db which realistically is as low as
you'll get.
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jelly head
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| posted on 27/3/14 at 05:57 PM |
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Yeah i struggled with the noise limit for the IVA and only got through after re-packing the (pretty large) silencer and slipping a wire wool rat up
the pipe!!
Perhaps some silencers are better than others though?
quote:
Originally posted by GreigM
Under 100db will be difficult - if you are "honest" about rev limits I doubt you will pass at a 3/4 max test. After struggling at a 105db
day at Oulton when they insisted on 7500rpm for the test I bought a large silencer and still only got down to 101db which realistically is as low as
you'll get.
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adithorp
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| posted on 27/3/14 at 07:58 PM |
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Mine was 98dB last time out at Oulton. They wanted 8000rpm but I peaked out at 9000.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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doobrychat
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| posted on 27/3/14 at 08:16 PM |
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does my head in noise testing at tracks... bikes:- 600cc or 750cc have a 7000rpm noise test.. 1000cc and up are noise tested at 5000rpm and i have
done a kazillion bike trackdays... turn up in a 1000cc car and then its 7500rpm noise test...
who makes this stuff up.. MSV, one rule for one and another for another..
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stevea
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| posted on 27/3/14 at 08:19 PM |
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Thanks for all the advice.
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motorcycle_mayhem
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| posted on 27/3/14 at 08:43 PM |
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Adithorp's R1, from what I have read earlier, effortlessly produces a million horsepower, silently.
My experiences are not exactly the same. Induction noise drive-by is your enemy at circuits so phonically equipped. The NIMBY''s have
noise meters in their village gardens, just down from Goodwood, and yes, their hands are on the phone to the Council when your car records. Goodwood
is a bit difficult.
Croft is difficult, as is Combe (very, for the same reasons) Cadwell less so. It may be small, but if you want to make a lot of noise, Llandow, or if
you fancy getting on the Belfact ferry, Kirkistown is surrounded by lovely tolerant people. Pembrey, however, is somewhat strict, as is Brands.
Statically, 102dB for me has been the achievable limit. It's the drive-by though. At Combe, the GSXR750 powered Westfield recorded 110dB on the
pit straight noise meter, all 16,000rpm of it. The R1 engine faired no better, the Hayabusa car (this year) was black flagged at Brands (yet sailed
through the static test).
An induction box will help, dramatically, but (in my experience) it's all a bit difficult.
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stevea
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| posted on 27/3/14 at 10:29 PM |
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One of my mates manages Croft so im gonna be spending a fair bit of time there in the future. So making that db limit is one I need to get to.
Although there are a lot of 105db there days now.
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Nick DV
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| posted on 28/3/14 at 09:27 AM |
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quote:
Originally posted by stevea
Looking fairly good so far. I guess the option is there for me to put a bigger silencer on and deal with the slight drop in bhp.
Is induction noise the biggest problem for drive by?
Quite simply, induction noise is the killer! Airbox is a must 
"The force will be with you, always!"
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