Last week I had the exhaust noise measured on my car at 107.9 dB at 9000 RPM. Too loud for a track day. I bit of silicon here and there plus some bonnet sealing foam tape reduced that to 106.7 dB. Lifting the bonnet off altogether only raised it to 108.9

I replaced my MNR stainless straight through silencer with an R1 can today. It is 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 went down to 101.6 dB. At 10000 RPM it was 102.4 on both the exhaust and non-exhaust sides of the car.
The noise went down to 100.6 dB. Interestingly it was 97.6 dB on the other side of the car but at 10000 RPM it was 102.4 dB on either side.

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 not 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? how I can get the MNR can to be quiter?

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




[Edited on 14-3-2006 by smart51]

Hi,

See my other link here:

http://www.locostbuilders.co.uk/viewthread.php?tid=40421

I'm after the same solution and within a few months, should have tested my Supertrapp, R1 and Yoshi can (which looks like it will be the best in-betweeny).

Pat...

118 dB. How? Are you using a silencer?

What have you done so far? I assume you've checked for air leaks. What can are you using?

Yeah, you might need one of those huge 7" x 30" numebrs Chris.

Pat...

I run a blade with an MK silencer on. must be about 106 db fortunatley Aintree is the only trackday that doesn't check noise level but they will pull you off if they think it is to loud which gives you a bit of leaway, the likes of donnington, oulton park if it ain't right you've waisted your money. A local bike racer said to me find out what the bike racers are running and use the same as the ACU have very strict noise levels at race meetings
tony

The ACU regs give a calculation for noise test engine speed based on the stroke of the motor. Would you believe I had my '06 ACU rule book here with me last week?

Normally, you're looking at about half max rpm with the meter 1 metre away from the end of the chimberley. The ACU limit at that is 105.something db (my TZ250 is bang-on the limit!!! ), but track day organisers don't seem to like this level....

[Edited on 13/3/06 by Coose]

TZ250 now that takes me back I was racing a TD1C when they first came out difference in speed was mind blowing, saw the light at the end of the tunnel and swapped over to racing sidecars
Tony

Ah, now this is a '94 v-twin......

[img][/img]

If you get it properly rolling roaded you'll most likely gain virtually all the lost power anyway, Richard Miles ran a standard R1 can on his R1 Striker and got some very healthy power figures and mine gave a reasonable RR figure whilst using someone else's engine map (ie mine hasnt yet been fully set up) so it can't be that restrictive.