Silencing?

[Tanguero]

Sound level meter arrived today so I had to try it out. 125dB at 4500rpm measured as per MSA regulations! This is not going to get me past the scrutineers for Brighton speed trial with a limit of 100dB!!! In fact at idle it is pushing 104dB

Currently I have TrackCar linked decats going into a sports exhaust that was on it when I got the car. Does anyone have any experience of ACT trackday silencers? I suspect they will struggle to get it under 100dB How quiet is standard back box on a 4.2? SP exhaust is a bit out of budget and I am not sure that would quieten it enough anyway.

Any other ideas?

[mike220]

Sorry I can't be of any help - but as I may be getting a Cerb in the v. near future I thought I'd enquire : If you get rid of the linked decats, will they fit a 4.5 ? If so, send me an e-mail if the time comes please.

Hope you manage to get things sorted and get her quiet enough to take part bud

Mike

[BCA]

• ahem* You'll probably have one of the quietest cars at the BSTs!

Our ACT silencers get the car down to 96db from 106db, but probably sap power... our car wasnt *that* loud compared to most, so you should be fine. Just remember to leave the handbrake on, or miss shift into fifth or something, we quite like the event being very much so err.. "ours".

[Tanguero]

mike220 said:

Sorry I can't be of any help - but as I may be getting a Cerb in the v. near future I thought I'd enquire : If you get rid of the linked decats, will they fit a 4.5 ? If so, send me an e-mail if the time comes please.

Hope you manage to get things sorted and get her quiet enough to take part bud

Mike

I am afraid the decats are specific to the 4.2 - the 4.5 needs a different length. I would like to keep them if I can get it quiet enough with them on. I only need the silencing occasionaly!

[mike220]

Fair play fella - that was one of my few complaints seeing the car today : I need to hear that sound more ! Was on standard pipes with cats in, perfect fro a trackday in terms of sound no doubt, but I wanna hear her sing if I get it ! haha

Hope you get sorted out.

Mike

[Tanguero]

BCA said:

*ahem* You'll probably have one of the quietest cars at the BSTs!

Our ACT silencers get the car down to 96db from 106db, but probably sap power... our car wasnt *that* loud compared to most, so you should be fine. Just remember to leave the handbrake on, or miss shift into fifth or something, we quite like the event being very much so err.. "ours".

I thought everything sounded fairly loud last year, but when I got my entry confirmation back last week, it had "noise limit 100dB NOT 103dB as listed" hand written on the bottom.

Given my recent showings ar Nort Weald I doubt you will have too much to worry about from me, unless I dramaticaly improve my launch technique!!!

What were your times last year?

[BCA]

12.79/ 116mph It is a properly slippery surface, not as grippy as santapod and the like, so that was a really good result for us.

I cant remember what the noise figure has been in previous years, but we've never had problems and are no where near the loudest of cars there... We run cats but have a sports exhaust (not good for power unfortunately, hope to sort that for next year maybe...)

[BCA]

Blimey, I believe thats three Cerbs confirmed for the event so far.

edit: Just re-read the figures actually... 125db @4500??!! yikes?!

What does it read at 3k rpm?? Thats what we're usually tested at (its a big lazy V8 that barely revs past 5.5krpm afterall) and its been between 104-106db for us usually...

Edited by BCA on Saturday 14th June 20:33

[FUBAR]

Ive just dug out my acceptance card...says "110dbs NOT 113dbs"

Also written above that is Handicap and under that SR.10. Anyone know what that signifies?

[Tanguero]

FUBAR said:

Ive just dug out my acceptance card...says "110dbs NOT 113dbs"

Also written above that is Handicap and under that SR.10. Anyone know what that signifies?

Just checked mine and you are absolutely right sir!! Only need to drop 16dB after all - hopefully the trackday silencers will do it!

Does anyone within reasonable distance of south london have a set I could try to see how much they quieten it, by any chance?

[Tanguero]

BCA said:

12.79/ 116mph It is a properly slippery surface, not as grippy as santapod and the like, so that was a really good result for us.

I cant remember what the noise figure has been in previous years, but we've never had problems and are no where near the loudest of cars there... We run cats but have a sports exhaust (not good for power unfortunately, hope to sort that for next year maybe...)

Good time!! though I was right - you dont need to worry!!! Definately more practice needed.

[Steve_T]

Peter,

I'd give Tim at ACT a call and ask him directly, it's got to be the easiest option.

Steve.

[Tanguero]

BCA said:

Blimey, I believe thats three Cerbs confirmed for the event so far.

edit: Just re-read the figures actually... 125db @4500??!! yikes?!

What does it read at 3k rpm?? Thats what we're usually tested at (its a big lazy V8 that barely revs past 5.5krpm afterall) and its been between 104-106db for us usually...

Just tested it again (much to he neighbours delight ) 120dB @ 3000rpm

[BCA]

ACT silencers can bring it down 10db in our experience...

The BSTs are going to sound even better this year!! Three Cerbs, blimey!

As an aside, we're not running in the handicap class this year, thankfully dad has got a National A license, so we'll run atleast three times I believe,

Edited by BCA on Saturday 14th June 22:14

[Tanguero]

Steve_T said:

Peter,

I'd give Tim at ACT a call and ask him directly, it's got to be the easiest option.

Steve.

I am planning to - just interested in other peoples experience too

[Byker28i]

Interesting. My old exhaust system was rear sports boxes - these in fact:


With cats they measured 104-106db, 96-98db with ACT trackday silencers. Without cats and act straight decats pipes I was 114-116db. MY SP system measures 109db without cats, 99-100db with.

Hope this helps.

[Tanguero]

My exhaust looks just like that.

What revs were your readings taken at?

Unfortunately I don't have a reading with cats on, but I guess that mine is another of these mythical "unusualy loud 4.2s"

[FUBAR]

Peter, Ive got some ACT silencers, but they are for the 3" system, so wont fit to 'try' if you have the 2.5" system. If you have the 3" system then you are welcome to try them (located 10 miles south of Gatwick...almost south London), but ACT are located near East Grinstead so half way between us. May be more sensible to contact Tim direct and 'try before you buy'?

I need to dig my sound meter out and test mine to make sure I can make the limit without having to use the silencers. Happy to test yours too if you fancy a drive south?

[Byker28i]

Tanguero said:

My exhaust looks just like that.

What revs were your readings taken at?

Unfortunately I don't have a reading with cats on, but I guess that mine is another of these mythical "unusualy loud 4.2s"

The original sports boxes were tested at 4k revs at various trackdays over the last couple of years. The SP full system is 109db on my car from about 3.7k revs upwards, but I've tested it, with/without cats at 4k and 4.5k revs. You'd be surprised how much difference the cats make in noise, which makes me wonder how much they are restricting the flow.

Most trackdays around me these days are asking for 4.5K revs

I have some ACT 2.5" trackday silencers, but I'm nowhere near you. The try before you buy idea is a good one. I assume they get slightly quieter as they coke up, but mine were pretty quiet from day one on the old system.

Edited by Byker28i on Monday 16th June 11:47

[BCA]

Byker28i said:

Most trackdays around me these days are asking for 4.5K revs

Why? Its a V8 that only revs to around 5k rpm, so even 3/4 revs shouldnt be that high??