Can anyone help clear up a few miths and answer a few questions on exhausts please.

1. For a BEC engine car max power at 9000rpm what engine speed will it be noise tested at for the SVA test. ?

2. Is it true that to quieten your exhaust if your baffle pipe has smaller perforation( more holes per SQ inch) this makes it quieter, or is the bigger the holes the Quieter ?

3. Lastly has anybody used a decible killer,
My exhaust baffle is 2 inch I/D with fibrglass wadding around the baffle and is repackable,does the wadding work better (ie silencing )if it loosley packed,or packed more densly.
I have a feeling it will be over the 101db on noise but not by much,so was thinking of putting the tapered cone type decibel killer insert into my baffle temporay,So do they work ?
Other alternative if this is correct, if I reduce the baffle I/D say to one inch will this make it quieter.
Also does anyone now of a make of high temperature silicone sealant that I can use to make the silencer gas tight when its re-assembled.

Well thats it now Im exhausted !

Any help advice appreciated

Thanks

Simon

1 - It's tested at 75% of max power rpm, so in your case 6750 rpm.

[Edited on 8/3/08 by matt_claydon]

To seal joints just use exhaust assembly paste,available in a tube from most motor factors.
And yes db's killers do work,they will knock around 5dbs off most cans,ideal for getting the car through sva,but they do sap a bit of power though,so loose it after.

[Edited on 19/05/04 by PAUL FISHER]

Firegum is the usual stuff for making up exhausts... Available from places like Halfrauds (or on Ebay )

Fibreglass packing is a tricky one. Pack it too loosely and it won't do anything. Pack it too tightly and it can actually stop silencing- in effect it just turns the can into a straight through stubby.....

I use bog (!!) standard silicone sealer for all my exhaust joints. As long as there are no bit holes or gaps to fill it works fine. Aparently, it gives off poisonous gasses with an exposure limit of just 4 hours so don't use it to seal up your oven if you intend to sleep in it.......

quote:

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Originally posted by matt_claydon
1 - It's tested at 75% of max power rpm, so in your case 6750 rpm.

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Thanks guys a few things to think about and try.

cheers

Simon