timmyb
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| posted on 12/9/06 at 05:28 PM |
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R1 engine/exhaust and noise restrictions
Hi guys,
"Tried" to have my first track outing in the MK Indy on Saturday at Castle Combe, but I was a league over the 100dB noise limit they
impose. Mine came out at 115dB @ 7000rpm (2004 R1 engine) - what exhaust box do you guys running a similar setup use to get under 100dB????
Tim
MK Indy R1
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cossey
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| posted on 12/9/06 at 08:30 PM |
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this the new r1 or the last of the old ones?
things you could try, non straight through exhaust (a chamber at the front with a partial baffle in it before the main tube/wadding part of the
exhaust)
sealed air box might also help as induction noise may be increasing it a bit too.
if it is the newer engine then make sure its a trackday without the drive by sensors as you mighr get it to pass a static at 7000rpm but it wont pass
at 11000+ where all the fun happens.
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smart51
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| posted on 12/9/06 at 09:00 PM |
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I have a 6" x 26" straight through can on my 98 R1. It measures 101 dB at 8800 RPM on my uncalibrated meter. on a 2004 R1, 3/4 of max
revs is 10300 RPM so for track days that will be really loud.
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dave-69isit
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| posted on 12/9/06 at 09:02 PM |
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hijack
colin has your cabel came yet
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DIY Si
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| posted on 12/9/06 at 11:33 PM |
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It should be 3/4 of max power revs, or so I've been told in the past. May differ from place to place though.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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TimC
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| posted on 13/9/06 at 05:47 AM |
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Talk to Simpson Exhausts. They do a pretty gigantic box which a lot of the Westfield guys/gals are using to get noise down.
I'll probably be going the same route with mine.
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907
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| posted on 13/9/06 at 07:34 AM |
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Food for Thought
Just a couple of points which may or may not be worth thinking about.
In my experiments with exhausts over the years I have found that the length of a can has more effect than the diameter.
For example, if you had a 125mm dia can 500mm long, and you fit a 150 x 500 you reduce the sound by say 1 dBa.
If a 125 x 600 can is fitted sound is reduced by say 4 dBa.
(assuming same design and materials are used)
To sum up, longer is better than fatter.
The other thing I notice is that bikes have enclosed engines, and within the bodywork are various bits
of stuck on foam or ally foil clad padding, partly to direct air flow, but also to absorb sound.
If I owned a BEC I would be looking at this as a partial solution.
Cover the inside of the side panels, bonnet, maybe fit a thin ally under-tray and clad this also.
Perhaps a layer of thin sponge behind air intake grills and outlet vents would help.
I think for very little cost a lot could be learned.
Sound reduction for no power loss IMHO is worth looking into.
atb
Paul G
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timmyb
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| posted on 13/9/06 at 08:46 AM |
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Cheers for the replies.
It's one of the last fuel injection models before the big changes. It confused me for a while - they seem to use almost the same castings on
the 2003/2004 throttle bodies as they do the carbs from the same/previous years! The exhaust box that's on at present came with the car when I
bought it, so I'll look into what exactly it is and put the info on here. I'm certain it'll be an MK supplied variant though.
I couldn't believe the figure that came out when the test was conducted though! My engine's running the standard air box, so I'm
confident that minimal nopise is passing over from that area too.
I did notice that the BEC's that did manage to pass the test and get onto track were running monsterous silencers. Unfortunately, I never
managed to find any of the owners near their cars to talk to them about it!
Where can I get in touch with Simpson Exhausts?
Many thanks once more,
Tim
MK Indy R1
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TimC
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| posted on 13/9/06 at 09:09 AM |
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Google is your friend....
http://www.simpsonraceexhausts.com/
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zxrlocost
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| posted on 13/9/06 at 11:27 AM |
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my r1 can was around 97db
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timmyb
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| posted on 13/9/06 at 12:47 PM |
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Cheers Tim, you're too good to me 
MK Indy R1
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amalyos
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| posted on 13/9/06 at 01:29 PM |
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I looked at turning the airbox around, but the spacing on the carbs are not equal, so it wasn't possible. I ended up making my own intake, and
got 95db at SVA using a 30" can from MNR.
Are the injection intakes equally spaced?
Steve.
 
Rescued attachment Airbox.JPG
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