smart51
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| posted on 28/2/06 at 12:31 PM |
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MNR exhaust noise level - too loud
I have an MNR exhaust with their stainless repackable silencer on an R1 engine. Has anyone had a similar exhaust measured for noise level for a track
day? What does it come out at?
Marc,
I guess you've had one measured for things like total kit car live and the donnington kit car show, as well as for racing.
[Edited on 3-3-2006 by smart51]
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marc n
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| posted on 28/2/06 at 12:41 PM |
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hi colin
yep for donnington we tested at 99 db with a decibel killer this came down to 95db on the r1, but we did have the silencer outlet pionting straight to
the meter rather than to the ground slightly
best regards
marc
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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procomp
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| posted on 28/2/06 at 01:58 PM |
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Hi smart 51 if you want it tested we have noise meters. the same as the msa use we are in birmingham.
cheers matt o121 350 3258
just ring if i can help you
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smart51
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| posted on 28/2/06 at 02:25 PM |
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Matt, that would be great.
Colin
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Agriv8
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| posted on 28/2/06 at 04:14 PM |
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Colin,
Another thing to consider is noise emmited from other sources not just the exhaust - engine noise ( from under the bonnet ) pannels rattling. intake
noise
another point is not everything that sounds noisey has a high DB level the V8 SOUNDS VERY NOISEY but at the SVA was well under the limits ( I think
this has a similar can to yours ( ok - well one each side )  .
We have the DB metter that you can buy from maplins think I bought it while it was on special offer. The SVA man kindly checked this on his
calibration machine and found it to read slightly out.
Make sure you let us know what it reads as this would be usefull for future queries not all MNR customers use this site.
Manj thanks
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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smart51
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| posted on 28/2/06 at 04:25 PM |
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I had an R1 can on for SVA. SVA said it was 100dB at 7600 RPM (2/3 max power). The MNR can sounds louder at tickover than the R1 can. Most track
days want to test at 3/4 of max revs which is 8800 RPM. I'm concerned that I won't meed the 105dB limit on the most generous tracks.
because of the louder can and higher revs. I'll ring procomp in a minute and book a test.
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Jon Ison
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| posted on 28/2/06 at 05:31 PM |
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At tracks with drive by noise meters you have to be on the ball, but at others Ive cut down the max rev display on the dash if that's makes any
sort of sense ? My old dash you could figure in max revs from 0-16000rpm, I normally set it at 12000 but for noise testing I used too set it at say
8-9k as there pretty cute these days and rather than take your word for it sneak a look at the rev counter for max revs rather than ask, if your dash
wont allow this then its of no use too you whatever, personally I wouldn't rely on a DB killer as I've had little or no joy from them, if
your at all worried get the noise down by other means.
Get a decent quiet system on, get it set up and leave well alone, whats the point in getting all your fueling and ignition spot on only too mess it
all up by fitting a different exhaust for a track day, the one time you would like to be running optimum engine set up ?
That's my take on it anyway.
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Avoneer
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| posted on 28/2/06 at 06:29 PM |
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Jon - what can do your run on you GT1 and is it quiet enough?
Mark - are you till selling your re-packable cans for BEC that Rizla had on his that proved to be really quiet?
Cheers,
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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smart51
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| posted on 28/2/06 at 07:07 PM |
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Marc,
what were you running to get 99dB? Was it similar to mine with a foam filter and no other sound proofing?
[Edited on 28-2-2006 by smart51]
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Jon Ison
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| posted on 28/2/06 at 07:45 PM |
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quote:
Originally posted by Avoneer
Jon - what can do your run on you GT1 and is it quiet enough?
Mark - are you till selling your re-packable cans for BEC that Rizla had on his that proved to be really quiet?
Cheers,
Pat...
£10 second hand Micron from clay x powersports and yes in that order, I've got the "kit car crisis" box in the garage, gonna try
that one when I fire it back up as its a "big" one and maybe quiet enough.
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smart51
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| posted on 3/3/06 at 03:38 PM |
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The nice chaps at procomp tested my exhaust noise level today. 107.9 dB at 8900 RPM. I need to lose 3dB or more to get in at loud track days.
What's the best way of doing this?
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amalyos
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| posted on 3/3/06 at 05:48 PM |
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What silencer did you have on when it was tested. I need to decide what to put on mine soon.
Could do with some advice before I spend.
Cheers, Steve.
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smart51
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| posted on 3/3/06 at 10:21 PM |
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I am using the repackable stainless steel can suppled by MNR. Marc recons the can should be quieter than this and thinks the noise must be coming
from elsewhere.
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amalyos
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| posted on 10/3/06 at 12:44 PM |
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What's the latest on the noise levels?
I'm thinking of getting a Std R1 can, but will this be any quieter than the MNR special?
Steve.
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smart51
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| posted on 10/3/06 at 04:07 PM |
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The MNR silencer is a stainless tube with end plates riveted in. This is so they can be removed for repacking. The gaps were not sealed and were
blowing. Also, some of the rivets were blowing through the centre. I have filled all these with clear silicone which seems to have worked.
I have put self adhesive chassis foam around all the bonnet joints to keep the induction noise in.
I was going to measure the noise agian today put it has been raining solidly since first thing so I won't be going out unless it stops.
The exhaust doesn't crackle so much on overrun now but I don't know if it is much quiteter. -3dB is only a modest change in perceved
volume to the human ear. -10dB is half volume at 3kHz so I wouldn't expect to be able to tell.
More news when it stops raining.
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David Jenkins
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| posted on 10/3/06 at 04:12 PM |
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quote:
Originally posted by smart51
-10dB is half volume at 3kHz so I wouldn't expect to be able to tell.
Almost right... -3dB is a half. -10dB is 10 times less. Don't worry about it though - few people get it right! 
See this link for a not-too boring explanation.
On a practical level, 1dB is roughly the smallest increment in sound level that people can detect.
David
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smart51
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| posted on 10/3/06 at 04:56 PM |
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No. Acually, -10 dB is half the volume as percieved by the human ear.
You seem to be thinking of POWER levels. -3dB represents half power on the logarithmic scale and -10 dB represents on tenth power on the logarithmic
scale.
I am talking about sound levels not noise power levels.
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amalyos
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| posted on 10/3/06 at 05:04 PM |
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Let me know how you get on.
Cheers
Steve.
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smart51
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| posted on 10/3/06 at 07:43 PM |
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When the rain stopped I went out to a quiet carpark near some woods. the background noise reading was 41 dB(A)
I set the sound meter to slow averaging max hold mode on a tripod 500mm away from the exhaust at 45°, at a height of 450mm (the lowest the tripod
would go)
at idle it read 89.9 dB
at 7500 (sva speed) it read104 dB
at 9000 (track day speed) it read 106.7
with the tripod raised to 550mm (hand height) those dropped by 0.5 dB
I moved the car to a different parts of the car park and read 108.2 and 108.9 dB
to gauge what difference the bonnet foam made, I took the bonnet off completely. the reading went up to 109.6 compared with 108.2 - a miserable
1.4dB.
at about 7000 or 8000, there is a lot of low frequency exhaust noise - like wind noise on an outdoor microphone but pulsing. by the time 9000 is
reached the engine noise seems louder than the exhaust.
There is panel vibration audible at 6000 - 7000 RPM but this is drowned out at higher speeds. this is despite me puting silcone everywhere.
The MNR can was noticably louder than the R1 can when I swapped them after SVA, yet Marc reckons that their can should be quiet. How can you tell
that there is wadding in the can without drilling the rivets off?
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David Jenkins
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| posted on 10/3/06 at 07:49 PM |
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quote:
Originally posted by smart51
I am talking about sound levels not noise power levels.
Here's a quote from that web site, when describing perceived loudness...
"Experimentally it was found that a 10 dB increase in sound level corresponds approximately to a perceived doubling of loudness."
Any misunderstanding is probably due to my far-too-long involvement in signal strength in telephony.
(don't worry - I'm not planning to start a row about this - life's too short)
David
[Edited on 10/3/06 by David Jenkins]
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smart51
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| posted on 10/3/06 at 08:34 PM |
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I didn't intend to sound at all angry, it was just that my tea was ready and I wanted to type quickly before logging off
I'd hoped that all that silicone and foam would have made more difference. Interesting that removing the bonnet had so little effect. Either
most ofl the noise is from the exhaust or the GRP is almost transparent to sound.
One test I intended to do but forgot was to measure the sound level from the other side of the car at the same position.
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smart51
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| posted on 11/3/06 at 10:53 AM |
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I fitted the R1 can today. noticably quieter but it messed up the midrange fueling. I leaned off the needles by 1 groove which mostly sorted it. It
is now slightly hesitant at full throttle.
The noise:
idle 87 dB
7600 RPM 100.4 dB (same as SVA)
8000 RPM 101.2
9000 RPM 101.6
10000 RPM 102.4
I measured from the same place on the non-exhaust side of the car just for fun
8000 RPM 97.6 dB
9000 RPM 97.6 dB
10000 RPM 102.4
It seems that my statement yesterday that at high revs the engine noise is louder than the exhaust was right.
Now the down side. Whilst the power delivery is smoother from 4000 - 5000, that is because it no longer jumps up at 5000 It now just rises smoothly
but bot as far. It feels slower all all engine speeds from 5000 up. I guess that's why I had to tweak the fueling.
What I want is something half way between the two, slightly more punch than the R1 can with only slightly more noise. any ideas?
[Edited on 14-3-2006 by smart51]
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progers
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| posted on 12/3/06 at 06:47 PM |
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I would guess that the fueling is not correct for the R1 can, even though you have played with the needles you may have to go down a jet size.
On my old MK Indy I originally had a modified R1 can and it needed 144 jets (I think). It made 138bhp at the wheels. Your car shouldn't feel
flat at higher revs.
I subsequently changed the R1 can for a custom 61/2" x 28" can to reduce noise and help improve power a bit. It needed 150 needles with
this free flowing can. Although the car seemed to rev out slightly more urgently, I wouldn't say the move from one can to the other was a great
difference. If your car feels that flat with the R1 can I would suspect fuelling before anything else.
If I were you I'd pick the can you want to use and then get the fuelling optimised on a RR.
Hope that helps.
Paul
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smart51
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| posted on 12/3/06 at 08:04 PM |
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quote:
Originally posted by progers
If I were you I'd pick the can you want to use and then get the fuelling optimised on a RR.
Yep, that's the idea. I just need to know which can to go for. Ideally, Id go for the MNR can if I could get the noise down by 5dB.
Otherwise, I'll have to get another can. R1 cans are cheap on eBay, and quiet enough as I have found. I take your point that some of the power
loss I have seen is probably down to fuelling but from the work I've done, I'd guess only half of the shortfall. The R1 can is more than
quet enough and I'd accept it being louder if it wasn't as restrictive.
My question: How can I make my MNR stainless straight through can quieter?
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procomp
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| posted on 13/3/06 at 09:21 AM |
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Hi if you want to try it we have the latest stuff that we are using on all of our more noisey racers. but like we said before there is no real way
that a straight throgh stainless silencer of that size is ever gonna work . usually the minimum required for trackday use is 28'' long
by 6'' dia and ally will always be quieter than stainless.
cheers matt
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