Silencing a Seven

[c7kjt]

Living in the South I have some great tracks nearby, such Castle Combe & Goodwood, trouble is my '86 X/Flow with rear exist pipe is never going to meet the tight noise regulations at these circuits.

 

Given the size of the silencer with the rear exit pipe I guess there's not actually much silencing going on. If I switch to a side exit box (and maybe a 4:1 front pipe) will this have the desired effect or are there other aspects such as induction noise (thru' carbs) to consider?

 

Ta muchly

 

 

 

Kevin Thomas

kevin.thomas@bigfoot.com

 

[Mike Bees]

Induction noise can be an issue, but it depends greatly on the state of tune of the engine. If your xflow is in a relatively standard form then a new 5 or 6" silencer should get you through noisy (105db) days at both Combe and Goodwood. Not sure about quiet (98db) days.

 

Mike

[grover]

Goodwood only test the static noise level at the exhaust. You could try a supertrap. These can get you down to the 98dB (5'' side, 4-1) limit but will effect performance at the top end.

I put a 7'' silencer on my VX 2L with a 4-1 competion exhaust and this got me down to a surprising 96dB static (I did lie about the red line!)

They can get you on the drive-by on the induction noise as you go past the pits. It's a good idea to change up about here if you see the marshall with his stick out!

[Jason Plato]

It is a sad state of affairs when our cars require silencing at both ends !

Still I guess things will only get worse ?

 

How do R500 owners get on at trackdays ? .... at a recent Castle Gloom trackday

"7 DUO " recorded 107db at 4500rpm and was promptly laughed at by the sound test man ! . How pissed off would I be if this happened to me in my gleaming R500 !!

( dream on ) .

 

Dave (98db) J

[CHRIS CLARK]

Not a problem with my 'lowly' 1400 SS. I'm pleased to say!

 

Peter c's exhaust might cause a few problems as he burns the noise meter mans trousers!!!

[Roger King]

Be VERY careful about using a Supertrap type device. We tried a similar device on the rolling road a few years ago and on a 200bhp Vauxhall we lost over 40bhp. Worse still, it sent mixtures haywire and at one point in the midrange full throttle application led the engine to become so rich that the engine would just stop!

 

If you do want to use one, consult the manufacturer and get it in writing that no damage or power loss will result.

 

Caterham's 'dustbin' size silencers work well, but Techcraft's (01926 403721) are just as effective and can be dismantled for repacking when they start to get noisy. The downside is that they are not made specifically for Caterhams and you will have to fit your own head and tail pipe.

 

Edited by - Roger King on 24 Oct 2000 18:32:04

[Paulplays-kool]

We recently fitted a 6" s/s silencer to a Vauxhall Caterham, significant reduction in exhuast noise, but an increase in induction roar. Trouble now is making the induction side quiet without affecting breathing.

 

 

Paul

[mark.hall]

Paul

Is the induction actually noisier, or just that the exhaust is now sufficiently quiet that it is more noticeablequestion.gif

Welcome to Blatchat by the way.

[c7kjt]

Thanks for the advice everyone.

 

Roger, Dependent upon Xmas bonus I'll probably be coming your way in the New Year for a (170bhp?) rebuild on my 25K mile old supersprint motor, I guess the exhaust setup is probably best left until then so something completely suitable is fitted.

 

I'll just keep annoying the neighbours until then!

 

 

 

 

 

Kevin Thomas

kevin.thomas@bigfoot.com