Muting the beast

[egilkv]

I am now the proud owner of a yellow 4.5 Cerb that I want to get through the registration inspection here in Norway.

With two tiny sports silencers in the back, she has a nice bark, but I'm rather convinced there is no way it will pass the test like that.

Any good ideas on how to silence her? It does not have to be permanent, I could live with some trick that may also mutes performance significantly just for this once only test. I guess an obvious choice is to fit an original back box, but they seem to be no longer available.

Cheers

[CerbWill]

Original style back boxes are available from ACT, pricey though!

[gruffalo]

But it sounds great and seems to release a bit more go than the louder systems.

[simoncrowe]

I have an original backbox if you need one?

[ukkid35]

simoncrowe said:

I have an original backbox if you need one?

It took me forever to locate a backbox, so if Simon's is for a 4.5 then I wouldn't hesitate for one second.

Now I have a Silverstone Performance unit that I use extra inserts with fibreglass wadding to help with noise tests at more demanding circuits.

[gruffalo]

OP, just how quiet does it have to be, the ACT back box gets it down to around 99db at 5000rpm on a static test.

[egilkv]

gruffalo said:

OP, just how quiet does it have to be, the ACT back box gets it down to around 99db at 5000rpm on a static test.

That sounds like something which would (just) pass my local trackday requirements, which is a good start.

The nit picking answer is that the sound level should be as TVR has stated in their type approval document, i.e. 75 dBA according to EC directive 70/157/EEC. (Of course we all know that in real life the cars left the factory with quite a bit more than that).

In practice, they will not measure this, so the practical answer is that it should not be so loud that "the man" thinks it must be far too loud. Depends on the man and his mood, then. Showing an exhaust system that looks like, or is, the original will surely help.

[gruffalo]

It sounds like the ACT system meets these requirements, I don't have cats in mine so assuming you will need these in place it should drop the noise level down a further 10db or so which for the test standard should be OK.

[egilkv]

simoncrowe said:

I have an original backbox if you need one?

Yes, absolutely. PM to egil at kvaleberg.no

[FarmyardPants]

ukkid35 said:

Now I have a Silverstone Performance unit ....

Looks like you have the 'low profile' version

[ukkid35]

FarmyardPants said:

Looks like you have the 'low profile' version

I have the TVR Glen version.

[mr shifty]

And if that doesn't work for you, I've got a spare ACT backbox and tail pipes.

[simoncrowe]

ukkid35 said:

It took me forever to locate a backbox, so if Simon's is for a 4.5 then I wouldn't hesitate for one second.

Is there a difference between 4.2 and 4.5 backboxes? I have 2 but I know one is for a speed 6 which I need.

[ukkid35]

simoncrowe said:

Is there a difference between 4.2 and 4.5 backboxes? I have 2 but I know one is for a speed 6 which I need.

Hope this helps

http://www.pistonheads.com/gassing/topic.asp?h=22&...

[Byker28i]

FarmyardPants said:

ukkid35 said:

Now I have a Silverstone Performance unit ....

Looks like you have the 'low profile' version

That's not the larger SP exhaust, which sounded great but was big, heavy. It's also fitting in the cutouts (well at least one side is). Long story of me and being ripped off with a SP exhaust

Plenty of ways of making the exhaust quieter. ACT have a quiet exhaust, extra silencing in the long centre pipes. ACT are also a very good company to deal with.

Cats of course, when fitted, are good for an 8-10db noise reduction (at around 4.5K revs) but will heat the cabin/gerbox/clutch. ACT also sell some decat replacements that are quieter versions of the straight through decat pipes
http://www.actproducts.co.uk/product/sjd02a-silenc...

For trackdays you can fit trackday cans into the rear of the exhaust - good for another 8-10db drop.

I have a decatted ACT system, similar to the big bore system here: http://www.actproducts.co.uk/product/sj10c-cerbera...
with ACT manifolds also. Noisiest I could get it was 116db by making it pop and back.
At 4.5K revs it's 106-108db, 98db with trackday cans on and 86db with both trackday cans and cats. At idle it's 88db as standard.

[tangerinedream]

In relation to putting an original exhaust on, I have just swapped a sports exhaust off and put the original exhaust (which came with the car) on. It's a bit quieter, but not as much as I (or more importantly my neighbour loving wife) was expecting. The car is decatted - not sure if this makes a difference.

[Incognegro]

I'll soon be having my ACT Decatted sport pipe noise tested for trackdays if I am struggling on passing I'll be going for this solution I think?

http://www.decibeldevil.co.uk/home

Anybody used before??

Thanks

[so called]

egilkv said:

simoncrowe said:

I have an original backbox if you need one?

Yes, absolutely. PM to egil at kvaleberg.no

Hi egilkv,
If you click on simoncrowe on the thread, it will take you to his profile where you will be able to email him your contact details.
Tony

[Byker28i]

Incognegro said:

I'll soon be having my ACT Decatted sport pipe noise tested for trackdays if I am struggling on passing I'll be going for this solution I think?

http://www.decibeldevil.co.uk/home

Anybody used before??

Thanks

Not those But I use these:
http://www.actproducts.co.uk/product-category/trac...
Worth 8-10db drop at 4500revs

[Incognegro]

Thanks for the heads up. I might have to speak to Tim... My issue is however I had my tips changed from the standard sports tails to Tips which are 4" diameter (outer) but they are dual walled. Te inlet diameter is 3" and they flare our to the 4 and have a length of about 8"

Still Im sure T will have a solution for me (I type with one hand as crossing fingers on the other).