How many db?

[cliff123]

What is the standard noise produced by the 4.0 chim, in standard spec (ie. no fancy exhaust or other mod's etc?)

Would like to do a few track days and notice they all have different noise level limits. Any suggestions on how and where to measure the noise would be appreciated?

[tamago]

at bedford they measure you when you rev to 4000 rpm with a reader around 1 mtr from the exhaust...
no idea what mine was prior to sleeving my pipes but they just waves me through... a standard Chim should be fine for track days nationwide....

[hongkongfooi]

For my 450 I had measured at goodwood on standard exhaust 93db one pipe, 103 for t'other, average 98 ish, so would have thought similar to yours maybe??

[shadowninja]

hongkongfooi said:

For my 450 I had measured at goodwood on standard exhaust 93db one pipe, 103 for t'other, average 98 ish, so would have thought similar to yours maybe??

average??! does the quieter exhaust of one muffle the noise of the louder one???

anyway, the standard one is less than 115dB, that's for sure. Goodwood measured mine at 115dB with the perforated pipes replaced by normal pipes (i suppose this is what some people refer to as 'sleeved'?).

[shillers]

Just for the record, 93dB and 103dB average at 100dB (because its a log scale).

[hongkongfooi]

shillers said:

Just for the record, 93dB and 103dB average at 100dB (because its a log scale).

Thanks smarty!

[cliff123]

well, went to goodwood, and had it measured. 93db from the left, 99db from the right! so, just passed the 98db limit!

why are they different levels? surely the exhaust are the same length? what else is happening in there?

[DustyC]

I noticed the exhaust goes 8-2-1-2* so perhaps at the point where it goes from 1 to 2 there is better flow to one of the tailpipes than the other.

(*manifold through to tailpipes)

[hongkongfooi]

A question I have asked before is here
[url]www.pistonheads.com/gassing/topic.asp?f=8&h=&t=84521