Reducing noise level.

[Polux RSV]

More and more tracks are requesting low noise levels. Some want 100dB on the main straight, others measures noise in static conditions. What is the best method to cheat the noise tester in static conditions? Reducing ignition advance? Adding fuel ?

Angelo

[Chris Wilson]

Fudging the rev counter, dating the noise tester's daughter, or back handing him a few $$ are all things that seem to work over here, allegedly

[Holmz]

More and more tracks are requesting low noise levels. Some want 100dB on the main straight, others measures noise in static conditions. What is the best method to cheat the noise tester in static conditions? Reducing ignition advance? Adding fuel ?

Angelo

Instead of cheat you could use a muffler.

[Chris Wilson]

I find a lot of measured noise can come from the induction side, especially with big overlap cams and high compression ratios. Silencing the induction is not something many people attend to on race engines, in my limited experience with induction attenuators they can make a surprising difference. Here in the UK noise is a big issue, and not being a particular fan of f1 it might be nice if in some countries they had to run silencers, and we mere mortals could plagiarise their development in that regard Stopping "stuff" resonating with the engine, and testing dog boxed cars with the clutch both up and down to see which is quieter can sometimes trim static noise levels a bit, as can lagging the exhaust primaries. I tend to go a bit OTT as nothing is more annoying than failing a noise test after a long period of car prep and a long drive to a circuit. PITA though, I love loud racing engines as much as most people.

[stevieturbo]

Really, what is the point in trying to cheat ? Just make the car quieter.

Yes it is crap, but it's the sad reality of the times we live in. Event organisers may do static or live noise tests. But Local councils can also have sound equipment as well placed around tracks or nearby. You wont cheat these. And if event organisers are found to be letting noisy cars out, the venues risk getting shut down.

Nobody likes it, but if people cheat and cause more friction between the idiots complaining about noise. The only losers will be people who want to race. As the tracks will get shut down.

All it takes is one idiot to make a lot of noise ( excuse the pun ) to the right people and even 1000 racers wont even get a look in.

[Polux RSV]

Stevie, I totally agree with you.

Let me precise why I need/want to cheat the static measurement. For bikes, static measurements on 2 cyls bikes are done at 4500rpm. Unfortunately, and despite muffler repacking and small outlets, my setup is noisy only in this condition, about 101-102dB. When running on the track, the motor revs no lower than 5000-5500rpm, and is way quieter than the inline 4. Bike was measured many times at about 95-97dB at full throttle. That's why I just want to pass the static test, which limit is set also at 100dB.

Angelo

[stevieturbo]

Really the only advice I can give then, is to buy a dB meter and test yourself.

They arent really that expensive, and then you can fine tune settings. But I found on my car that tuning to a normal lean mixture, say 14.0-14.7 etc and reasonably high timing was quietest. Running rich definitely made it noiser. Timing didnt have as much an impact though.

But in the end I did just fit the biggest silencers I could as well. As I also got fed up with the noise. My bloody supercharger makes more noise than my exhaust now during the test !!