Sound Testing

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AJRJ
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Re: Sound Testing

Postby AJRJ » Wed May 31, 2017 2:01 pm

Well, it depends :D

Some 450s are quieter (Honda) or louder (Kawasaki) with KTMs somewhere in the middle? Most bikes should pass the FIM test that's randomly employed now.

For the spark arrestor it is not required to deviate from stock, but encouraged. We all want to be responsible in our new environment of extreme scrutiny. Consider the use of a FMF Q4 or similar if possible.

:thumbsup:

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malcolmzilla
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Re: Sound Testing

Postby malcolmzilla » Wed May 31, 2017 2:32 pm

2015 YZ250FX stock exhaust FAILED Idaho City 100 testing in 2016, USFS 96dba limit I believe.
This is the "euro" mx can on the FX models, so is supposedly quieter than North America MX version (YZF).
15 Yamaha YZ250FX, 270cc, cams
15 XC250
11 Berg 570, dualsport and supermoto
17 PW50
78ish CT70
Just another Dirt Donkey...

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Hooligan
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Re: Sound Testing

Postby Hooligan » Wed May 31, 2017 8:24 pm

How is the test done? And what is the limit?

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malcolmzilla
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Re: Sound Testing

Postby malcolmzilla » Wed May 31, 2017 10:32 pm

Idaho city 100 they place a microphone by exhaust blip throttle. Spark arrestor test is rod inserted into pipe to see if it stops before full insertion.
15 Yamaha YZ250FX, 270cc, cams
15 XC250
11 Berg 570, dualsport and supermoto
17 PW50
78ish CT70
Just another Dirt Donkey...

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Hooligan
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Re: Sound Testing

Postby Hooligan » Thu Jun 01, 2017 9:11 am

How is the mic oriented to the exhaust tip? How far away? What RPM?

All of those things are gonna have a major impact on the noise level. The decibel scale is logarithmic, which means that small value changes can represent huge difference in noise. For example, 3 dB represents a doubling or halving of the noise level, while 10 dB represents 10x the noise level.

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AJRJ
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Re: Sound Testing

Postby AJRJ » Thu Jun 01, 2017 12:26 pm

The FIM recommends the "2 metre Max" method.

The mic is 2m away from the exhaust outlet at 45 degrees, and the motorcycle is help at max RPM for 1 second.

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