But anyway 98 to 105 is quite a jump.
I've got a track day on Friday at Brands and have just learnt that they have started doing static noise tests. I've recently changed the
manifold which meant I had to use a standard 5.5" Westfield silencer instead of my old 6.5" silencer. I have a standard Vx engine with
170bhp. On the old silencer it was 98.7db. What do you reckon the chances of me being under 105db with the 5.5"? (I know this is like asking how
long a piece of string is, :durr: but I'd be interested to hear people's views.)
It sounds a bit louder, but nothing dramatic. I would have thought that an extra 6db would be very noticeable.
Any tips to get it through if it fails first time?
Because it's a log scale each dB is quite significant in terms of change of noise scale - IIRC 110dB is twice as loud as 100dB. No doubt someone
will delight in telling me if I've misremembered!
But anyway 98 to 105 is quite a jump.
What size is the tail/through pipe Phil and how long is the silencer? Is it still on carbs?
look on maplins web site; they sell a digital sound meter, not locost ~ £ 50 and a DIY kit £ 6 but the kit doesn't look like it will give much of
a resolution.
buy the maplins, use it then return it saying it was all a bad mistake etc: within the 14 day period.
quote:
Originally posted by ned
What size is the tail/through pipe Phil and how long is the silencer? Is it still on carbs?
Every increase of 3dB is twice as loud. Std log scale.
every 3dB represents twice the power but 10dB represents twice as loud as heard by the human ear. 1dB is often said to be the smallest increase in
sound pressure level that you can "hear".
I changed from a 5" to a 6" silencer on an R1 engine and lost a couple of dB. Packing will affect it too but remember that not all of your
noise is from the tailpipe. Noisy induction and panel resonance makes a difference.
I was talking to someone on Monday who swapped his pipercross filter for a K&N on his crossflow. For the first time he can hear an exhaust note
under the intake roar.
What do you reckon on stuffing a handfull of wire wool up the pipe, held in with some chicken wire, if it fails?
quote:
Originally posted by Phil. S
Bit of a desperate post really, but if I fail, I'll have a wasted trip and will lose my money, so it's a bit of a worry.)
Are there any racing circuit nearby? Most would be willing to do a noise test for you, especially if you suggest that you might be attending an event there depending on noise levels.
Castle Combe is an hour's drive away, but I'm not sure if I'll have time to do this tomorrow even if they could fit me in. Might give
them a call though. They also sell little add-on silencers if it's too loud. Looks stupid but would do the job.
What about the wire wool trick as a quick fix?
[Just phoned Castle Combe. They can't do it till 19th Feb.
]
[Edited on 7/2/07 by Phil. S]
peice of string average length 30m
Phil,
I would reckon you will be fine, my Indyblade is about 104.9db! and yours is nowhere even near as loud as mine.
I would be very very suprised if yours is anywhere near 105db.
Rich.
[Edited on 7/2/07 by shortie]
I'm sure you're right. It's just one more thing to worry about (apart from the crap weather for Friday). I'll take some wire wool,
chicken wire and a hose clamp just in case though.
quote:
Originally posted by shortie
Phil,
I would reckon you will be fine, my Indyblade is about 104.9db! and yours is nowhere even near as loud as mine.
I would be very very suprised if yours is anywhere near 105db.
Rich.
[Edited on 7/2/07 by shortie]
If you do the wire wool trick be careful to make sure there is definitely NO chance of it shooting through the silencer and out the tailpipe.
If you fail then I'm def stuffed for my next Brands Hatch day!!
Rich.
The idea was to stuff about three inches of wire wool up the tail pipe, cover the end of the pipe with chicken wire, then clamp the chicken wire to
the exhaust using the hose clamp. I told you it was a bodge! But apparently, it is very successful.
quote:
Originally posted by shortie
If you do the wire wool trick be careful to make sure there is definitely NO chance of it shooting through the silencer and out the tailpipe.
If you fail then I'm def stuffed for my next Brands Hatch day!!
Rich.
Sounds like it should do the job, will have to remember it!
Let me know how you get on mate.
Rich.
quote:
Originally posted by shortie
I would reckon you will be fine, my Indyblade is about 104.9db! and yours is nowhere even near as loud as mine.
quote:
Originally posted by shortie
Sounds like it should do the job, will have to remember it!
Let me know how you get on mate.
Rich.
It's a bit loud but def doesn't sound over 105db to me.
Rich.
Oh well, I've packed my wire wool silencer kit, and will see how I get on. I'll let you know if there's a problem. If there is, I'll be looking for a bigger silencer.
I had mine rmeasured at 108 when I bought it and it was f'kin load.
I changed silencers and got down to 95db and the difference was phenomenal.
As said, every 3db is twice as load so you have a fair margin to work with.
I would also try quietening your inlet as much as you can with a box as this makes big difference.
quote:
Originally posted by TangoManAs said, every 3db is twice as load so you have a fair margin to work with.
Well despite my worries, they decided not to bother with the static sound test. So I still don't know how loud my car is. It didn't have any
problems with the drive by test though, so I guess it can't be that bad.
On a different topic: my first attempt at in car videoing doing go very well. After recording two sessions, I couldn't get teh camera to work
(though it seemed fine when I got home). Also my bright idea of making a polycarbonate windscreen for the camcorder to protect it from spray and
stones didn't quite work. You'll see what I mean from this clip from the second session...
http://media.putfile.com/Brands-Hatch-track-day
So a disappointing start to incar videoing. I hope to do better next time.
Cheers
Phil
[Edited on 11/2/07 by Phil. S]
Phil,
If you're concerned about a clear view for the camera in the rain, make a rotating disc from clear poly (or similar), that as it spins, throws
off water.
Wouldn't need to be too big.
I can't remember what they are called, but quite common on boats
ATB
Simon