Noise limits on circuits - bliss with new Powerspeed

[McBreadhead]

I am having the exhaust can replaced by Powerspeed and wondering what noise limit to go for balanced against having too large a dustbin on the side of the car.

 

They are suggesting a 7" can to cover all bases but it dominates the car whereas I am thinking perhaps 6" might suffice. Engine is a 1760cc Xflow with 4-1 primaries.

 

I am in the south so likely to visit circuits like Thruxton, Goodwood, Castle Coombe, maybe others in Midlands. Castle Coombe has limit of 100db(A), which is measured at ½ metre from the exhaust outlet at 4500rpm. Goodwood has a 105dB track day but I think they do quieter ones. Thruxton says Maximum 90db @ 0.5m/45 deg.

 

Confused and looking for advice on this one please. Cheers, McB

 

Edited by - McBreadhead on 20 Jun 2011 14:39:54

[BenF]

McB

 

I would go for the biggest can possible, even if it takes you well below 100dB. Noise restrictions are only ever going to get tighter and it will give you more choice in track days

 

Ben

[Fishy Dave]

Ithink you may have to give up on Thruxton, it would be hard to get a Caterham that quiet and still give the performance and fun you'd want. The odd trackday they do there is generally aimed at 'normal' looking road cars with no hint of race car about them or else they have complaints from the neighbours!

I did a trackday there years ago in my Celica 190, and their were a number of BTCC and Clio Cup drivers practising there in hire cars (Mondeos and Focus with Avis and Eurocar stickers on)! 😬

[jonboylaw]

Go for the 7 inch..

You will probably find that the induction noise will then become the biggest problem :)

Also make sure the manifold fitting gives a good pinch on the exhaust gasket to avoid it blowing, this can add a lot of high pitched output..

 

 

[McBreadhead]

Thanks for the replies - looks like 7" is the way to go then.

Re exhaust gaskets I already have 7 Workshop copper items which work fine - I assume you are referring to this area JBL or were you referring to elsewhere?

 

[jonboylaw]

Yes, this is the area, so just make sure that they do not "oversize" the exhaust ports on the manifold too much else you will never get a good seal, even with the copper gaskets. Take the gaskets with you so they can see the max bore they need on the manifold.

 

Jon

[McBreadhead]

Hopefully not a problem as I am leaving the primaries alone, it is just the silencer and 4 into 1 union that is being altered

[Drumster]

As a reference, my 1800 x/flow with 4-into-1 and 6" Tech-craft silencer used to register around 95-97 db at 4,500. The secret is not to pack in the exhaust padding to tightly.

 

Now I've gone Zetec with 4-into-1 and 7" silencer I was recorded at Goodwood in April as 92db at 4,800 and at Curborough a paltry 88db around 4,200

[McBreadhead]

Picked up the car on Sat with new Powerspeed 7" can. What a difference. And a nice installation too.

 

The old std Caterham unit was a duffer and always bottomed out - the design was way too low. The Powerspeed has a neat little S-kink section between the 4 into 1 collector and the can which raises it up nicely.

 

Any yes induction noise is now dominant!

 

Now for some track days......