Exhaust noise

[forumadmin]

Did a track evening yesterday at Donington. Yes, yes I know I am getting in some cheating bastard practice before the Silverstone event. :)

Anyway a couple of points, the noise limit at the event was 98dB drive by. Surely no problem? I mean my car which reads 94dB on a close up static test will be ok, right? Wrong, I recorded a 99.7dB while going past! They let me off with one warning, and I kept the revs down to 5000 and no full throttle for the rest as was OK.

So looks like the standard exhaust will be on for Silverstone, unless I can find some better inserts (mine don't do enough). I think my exhaust is getting louder over time.

[modarr]

You still here?
Didn't think push bikes had exhausts other than the fat bastard on top farting his pies out?

What diameter insert you running? Is it perforated tube wrapped in exhaust wadding?
I found that when the MX5 started farting too loudly, a slighter narrower tube/more wadding or in the end, actually hammering the insert end into a smaller diameter opening (creating an inwardly curving tip to the end going up the pipe) slowed down the gas enough to spend more time absorbing noise.

I even tried a narrow perforated tube that fitted inside the first, Russian Doll style, to really cut the noise as after a few black flags, paranoia sets in.

[forumadmin]

Yes I'm still here, and still willing to kick chump ass on a track until I leave. I have to make the most of living in a country with racetracks.:( The car performed awesomely at Donington, and being a Lotus Club day drove rings around the Elises and Exiges there. New suspension is the business. I took a girl friend with me, who can drive on a track and even though first time in my car, and at Donington, and immediately went out and kicked ass too. She's a lifelong Lotus fan and owner, but is a convert to the NSX now.

I wasn't using any inserts. The ones I made only reduced the levels by a couple of dBs, and as the system seems to be louder now than when I got it I'm not sure my homemade ones will be enough. I also think I can notice a difference in performance.

Should be conducting some sound tests with Paul soon to find a solution.

[simonprelude]

The monitors at Donington are very err........... conservative on the side of the conservatives, or indeed liberal for the noise abatement society.

My S2000 was recorded at 103dB's a couple of years ago at flyby, the same as a Lamborghini Murcielago. I simply added the silencer and kept off the loud pedal and had some fun at low revs instead, the Lambo simply went home.

The silencers should lower by 3 to 5 dB and in real life terms be fine, just not at Donington.

[markc]

You've got me worried for Silverstone now Kevin :(

Were you noise tested statically at Donington... what did you register? Sounds like the 98dB level was measured by trackside monitors?

What noise level did you record at Bedford when we were there in '07? Did you get 94dB there or was that from your own meter?

My Dali is a bit louder than your Taitec so I have to be extra careful.

Any advice on where I could get some reasonably priced insets/baffles for my 3 inch tailpipes? I'm not paying £100 each Supertrap prices.

Hopefully Silverstone/Goldtrack will be more helpful with their noise measurement equipment and attitude.

Cheers

Mark

[modarr]

Make your own with a perforated exhaust tube of your chosen diameter and wadding from Demon Thieves.
Cut slits around the edge, fold out flat with hammer, srew in place when required.
Mo