Simon
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| posted on 3/3/03 at 12:52 PM |
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Noise!!
Chaps,
I'm building my exhaust and a friend is concerned that I'll fail the noise test!!
SVA manual states 101 db at 75% of max revs or 66% of max power or something along those lines.
Exhaust is 1/5" headers into a pair of collectors (one each side) into a pair of 2" pipes (one each side), then into a couple of Cherry Bombs (one
each side!).
My understanding is that 101 db is actually very loud.
I need some eg please - ie pneumatic drill is 90db?
Thanks
ATB
Simon
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sg_frost
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| posted on 17/3/03 at 01:20 AM |
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Road rally cars are tested at 98dB at 4500rpm, get down to a local rally and try to have a listern. 101dB is loud!!!
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Simon
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| posted on 17/3/03 at 09:43 AM |
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Excellent:-)
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andyd
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| posted on 17/3/03 at 12:30 PM |
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Simon,
Have look here http://www.bookatrack.com.
They will hire a digital noise meter for £9 inc for a few days. You can then test out if your system is too load 
Click the miscellaneous link at the bottom of the shopping links on the left hand side at the top
HTH
Andy
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Northy
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| posted on 17/3/03 at 07:05 PM |
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You can't just go waving a sound level meter at your car, and reading the value on the screen.
There are standards writtern telling you how to take measurements, so far from exhaust, at a cetain angle etc etc.
My job is designing sound level meters, and I'm hoping to get hold of the standard if anyones interested.
You can't say 101 dB is loud, it depends on soo many things.
PS, while at Tiger on Saturday I saw their sound level meter which I was told was the same as used at SVA, I had never heard of the make! Look on the
back, make in China. No mention of any standards etc. If my car fails SVA on noise I'll start asking some awkward questions 
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing! 
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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kingr
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| posted on 18/3/03 at 10:21 AM |
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IIRC it's 1 metre at 45 degrees off the exit of the exhaust.
Kingr
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david walker
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| posted on 18/3/03 at 07:48 PM |
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If you are building a V8 Locost and going to have an exhaust outlet on each side of the car then you are at an advantage with the "1 metre, 45 deg"
rule!
Also Rover V8's, despite their engine size are not particularly noisy, ie don't have that shrill noise of some smaller 4 cylinder cars.
I failed my initial SVA on noise, coming in at 105dba. I debated with myself about challenging the result, ie asking to look at the certification for
the meter etc, but decided against it. The examiner had been pretty fair anyway. He told me to stuff some wire wool up the end of the exhaust and come
back! I did, and passed at 98dba.
He told me that an Ultima had failed the week before at 115dba - now that is noisy!
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
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locost7-online.com
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| posted on 18/3/03 at 08:20 PM |
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Dave, where did you have your SVA? Notts? i failed on noise there too, 105db with a 1300 xflow! standard but on carbs x2, the pipe im using is from
stuart taylor motorsport, i was suprised to fail
Locost Xflow 150bhp injected! Sold :-(
Facebook blog https://www.facebook.com/Johns-Tiger-Avon-Build-814223212056368/
PLEASE NOTE THIS MEMBER IS NOT A TRADER.
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david walker
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| posted on 18/3/03 at 10:07 PM |
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John, yes it was Notts (Watnall).
I have a home fabricated, 1.75" bore stainless system, it exits at the back of the car, but there isn't much in the "silencer" box!
I'm used to noise testing at motorsport events and to be fair I suspect his 105dba was probably right.
He checked my noise level at 4500 revs and I also considered arguing that this was too high. I have lent my SVA manual to another builder so can't
check it, but I recall the rpm level rules being ambigious and felt worth an argument!
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
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