Thoughts on a second silencer?

[SLR No.77]

My 1999 SLR runs with a Caterham o/e cat bypass pipe and a 7" BTB silencer.  Hopefully this week I'll find time to re-pack the BTB silencer but I've wondered whether it would be feasible to use the old cat pipe (which is pretty shot) as the basis for an addition custom short silencer. Has anyone any experience running with a second silencer, and any thoughts on whether it would have any effect on noise reduction, being quite short?  I know from running a classic Mini a twin box system is certainly an improvement over just a single box.

I've not used the car on track in years and I'm finding we spend more time touring these days, plus I'm not really into super-noisy exhausts. Also the rear exit Caterham setup has practicality issues so not really an option.

Thoughts?

Stu.

[Geoff Brown]

Too much weight !!

[SLR No.77]

Pardon Geoff?

But seriously ... I suspect a cat converted to a silencer will weigh less than the original cat!

[PlastererPete]

Back in my younger days a couple of friends took to knocking the gubbins out of theirs cats for "performance gains". I doubt it will weigh much more than the decat pipe after its knocked out. 

[ECR]

 Only way I can avoid being ejected on a lot of circuits !

[SLR No.77]

That's a trombone Roger!

[Nigel Blandin]

Here's a , probably dumb, question...

If you put a turned down exit pipe on a standard exhaust would that make any difference to drive by readings?

Like Roger, my exhaust is on the proper side and therefore blows to the outside of clockwise circuits. Certainly Goodwood and,  I suppose, others take readings on the outside of the circuit because that's where the complaints come from.,

[aerobod - near CYYC]

Turning down the exhaust (or better inward to reduce reflection off the ground) may knock down a marginal reading. At the Rocky Mountain Motorsports track that I use they have the most sophisticated noise measurement system that I know of, that was installed last year. It has several noise measurement points on both sides of the track that are linked to GPS monitoring of every car position (which is also linked to the electronic flagging system). My R400D was typically giving 5dB higher measurements on right side vs left side monitoring points.

[Gareth H]

I've been having similar thoughts about my CSR, which will be used mostly on the road, it already has a big silencer, and wondered what effect putting in a link pipe on the exhaust outlet to exit at the rear of the car rather than next to my ear might have.