Noise Issues

[Krazyken]

As we all know if you want to take your car on track you have to be below 100dB otherwise you will usually get sent home unless you are at Llandow or Pembrey.  With the mods to my car over the winter incl. bigger inlet, ported head & longer exhaust primaries I was expecting a small increase in noise but as I have been regularly 97dB (or 98dB at Combe) and the noise level doubles every 3dB I was not unduly worried about it.

I drove to Combe on Saturday morning and went straight in for a noise test to see where I would be.  The testers at Combe have a reputation for being around 1dB higher than any other circuit so I was quite pleased when the tester showed me that I had peaked at 99.8dB at around 4700rpm.

Imagine my dismay then when talking to friends I knew in the paddock who were going out on track all told me that they had all measured around 2dB lower than normal!!  That would put me up to 101.8 dB and on my way home from a track day.  I later spoke to the noise tester and he assured me that the noise meter had been calibrated at 8am that morning.

Before I spend another small fortune on a new silencer box, MSE will have their noise meter at Pembrey and I can get a second opinion.  Has anyone else ever had a wide variety of dB readings?

[stupott901]

I was reading between 99 to 101 at keevil with mse and that was after me getting tested before hand and it read a max of 95 db

[David H]

I have varied loads over the last couple of years, all on the same engine. I have been as high as 99 at Combe and as low as 94 at Combe..... with the same exhaust. 94 was Saturday. The temperature of the engine seems to make a difference. If I'm warm but have rested the engine, i.e not idled it before the sound check but for a minute, the test seems to come back lower by a decibel or two.

This could be total nonsense but its like a lucky pair of socks....

Sound checks are so iffy as the weather, the person doing it, the time of day, pressure in the air etc all make a difference. My dad's MG went down from 103 to 98 with only one of the two exhausts having a 'Merlin special' stuck on the end. That basically made the noise nearly a 3/4 quieter. Really?? It didn't sound ANY different to me.

Still I'm glad they let him through as I got to drive it on track and what a hoot it was!!

Anyway Ken. Maybe try new fluff in the can?? Or slip em a 20 when doing a sound check. This sound check business is a proper pain. Why move to a town called Castle Combe then start complaining about noise from a race track?? Its been there a while.

['The Gaffer']

98 when I got tested at Combe on Saturday, yet the time before I was tested at 99.9 and just scrapped though... Thats odd I thought

[Krazyken]

Thanks for the feedback guys, it seems that noise testing is as reliable as the weather.  I will see what MSE come up with at Pembrey and report back.

[David H]

More importantly.... how was the car after all the upgrades?

[Krazyken]

I will find out at Pembrey but there is definitely better throttle response, more power & torque.  I collect the car from Marlin tomorrow with the new front spoiler and rear diffuser fitted so Pembrey next weekend will be the "shake down" test.

Next step is to panel in under the engine to get best use from the diffuser then have some dive planes designed & fitted on the front.  That will then be it for the Marlin it will have been developed as far as it will go.  The next stage after that would be to buy a Radical, R500, Atom Supercharged, Ultima GTR, GD T70 or just keep it as it is and be satisfied with that.

That's the problem with kit cars you can just go on & on & on & on & on....... you get the idea.