I’ve been thinking about ways of reducing exhaust noise and want to invite opinions on an idea of mine. I have a link pipe between my exhaust collector and silencer that could be up to 145mm plus another 30mm or so that pushes into the collector and the can. If I were to have a silencer made with 2” OD tubes with a can 140mm long and 6” in diameter, would I get a noticeable improvement in silencing?

My car was measured at 102 dB(A) at Elvington last year (at 2/3 peak power) I would like to lose at least 2 or 3 dB to get in at some of the more sensitive track day circuits or better still 5 or 6 dB to qualify for Donnington. Is that a reasonable expectation?

Hi if you remember the one i was going to make.

I have one on a car now that has made a huge difference during testing. Your welcome to pop in and see what you think .

cheers matt

I'll be fabricating my new exhaust next week and will test it two weeks later.

But based on what I have learned from various reply's on a former thread it should help. Conclusion of the reply's and u2u's:

- More volume in the exhaust makes it quieter.
- More lenght in the exhaust makes it quieter.
- If the flow has to make sharp bends it will increase backpressure: usually reduce power and increase torque
- Wall stiffnes of the silencer is a big factor. A lot of sound come from the silencer itself as a 'boombox'

One person claimed he had made HUGE improvements by watercooling his exhaust. 5mm of water around the silencer plus some piping inside linked to an electrical pump and bike radiator mounted on top of the silencer. This cooled the air; made it denser and thereby reduced the speed in the silencer. Am still waiting for a picture but the idea doesn't sound that bad to me. I know they use that solution sometimes in industrial applications. Don't think it is practical for a seven though.

I would create a 'wall' in your 6"pipe roughly 50mm after the beginning. And in this wall fit 70mm small diameter pipes pointing backwards; as small as you can get as long as the total square area is slighly more than the 2" intake and exit.

Matt's solution is tested so if it is simple and it works; go with that!

Rgrds,

Mies

I did something similar last year as a trial in adding a small silencer, cut down custom chrome 5" unit to fill the gap. Very effective but haven't done any trackdays since to get the noise level measured. I would guess it's now 95 ish. No apparent loss of power. Must get one properly fabricated because it does look gross.
Rescued attachment extra quietness.jpg

Thanks Dusty. What was the noise level before you added the extra silencer?

100. Loud enough to be a pain after half an hours driving and to have tinnitus for 12 hours after a 250mile trip.

Have you had a noise test done since the new engine was fitted?

You're old engine had a fair few problems and it's possible they could have contributed to the noise issue. Mine went through SVA well below 100db with the MNR can.