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

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.

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.

colin has your cabel came yet

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.

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.

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

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

http://www.simpsonraceexhausts.com/

my r1 can was around 97db

Cheers Tim, you're too good to me

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