Managing exhaust noise limits - teased from Japfest thread

**Lasitha** · 05-02-2006, 17:40

They don't work at all for our cars.
I rented one of these from a garage outfit that was at a Bedford trackday last year. I didn't even manage a single lap till i got black flagged...I was running an Apex type 1 cat back with de-cat and front pipe...

They work on N/A cars but not turbo'd ones.

**bren** · 05-02-2006, 17:56

Our S13 ran 100 yesterday with one of our new decat silencers. Thats a drop from 107ish

SM · 05-02-2006, 18:00

Originally Posted by bren

Our S13 ran 100 yesterday with one of our new decat silencers. Thats a drop from 107ish

Wondered how you passed the 105dB limit

Is that a Apex single box, or twin box, system + decat silencers.
I had it in my head you were running a silenced front pipe + single box system only.

**bren** · 05-02-2006, 18:11

Twin box with one of our new 3" decat silencers

I measured it as 95db, as did gary. Ann says BAT measured ti as 100db but maybe shes wrong seeing as both Gary and I got 95. Its certainly not anywhere near as loud as it used to be.

**Matt_S** · 05-02-2006, 20:28

Originally Posted by mambastu

115dp ? No, 115 db

You can literally hear the car howling from a couple of miles away when its on full chat. The weird thing is I don't get the uncomfortable resonance inside the passenger cabin that I used to get with the Nur Spec R when I had the CA in the car which makes the exhaust much more bearable with the bung out than it used to be......er....either that or I've gone deaf

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Yeah I found that with mine. First time I heard it I couldnt believe it!!! It sounds like a bike!!!

And youre right about the incar bit. ITs nowhere near as bad

**cHiL** · 11-02-2006, 20:29

Originally Posted by yeager

Ideally I would like to have something I can change easily. Looked at these options;

Apexi Exhaust Control Valve
http://www.apexi.com/product_exhaust...=251&pageNum=1
But it kills power too much.

If I had 2/3 silencers I could swap into the decat space, each giving me 96/98/100db's that would be ideal.

I have an APEXi ECV fitted but I took it to an engineering factory first and had the bore increased to 3 inch so as not to kill power. They charged me all of £20 to do it. It's my intention to have the valve "flap" itself increased to 3" to match so I can close the zorst right up if I want but at the moment it takes the DB right down to 94 with only the 67mm valve in the new 3" hole. I have been on track at CCoombe and Silverstone with this fitted and all I did was open the valve again when I got on track. I was never stopped or tested again but if I was tested again I would just pull the valve shut again

**archenemy.co.uk** · 13-02-2006, 07:41

Originally Posted by cHiL

I have an APEXi ECV fitted but I took it to an engineering factory first and had the bore increased to 3 inch so as not to kill power. They charged me all of £20 to do it. It's my intention to have the valve "flap" itself increased to 3" to match so I can close the zorst right up if I want but at the moment it takes the DB right down to 94 with only the 67mm valve in the new 3" hole. I have been on track at CCoombe and Silverstone with this fitted and all I did was open the valve again when I got on track. I was never stopped or tested again but if I was tested again I would just pull the valve shut again

Don't go to a place like Bedford

There are no second chances on the drive by tests, you pass a station, too much noise = bye bye

**cHiL** · 13-02-2006, 07:44

Drive by tests? what, on a public road or do you mean on a track?

**cHiL** · 13-02-2006, 07:55

As far as I'm aware the track at Bedford has a 101db noise limit and quite frankly my car would pass that without any form of silencing and thats with well over 300bhp and a GT Spec zorst(3.74inches). I think it's usually the cheap exhausts that make over 101db... oh yeah, and the nur spec..

**archenemy.co.uk** · 13-02-2006, 08:17

Originally Posted by cHiL

As far as I'm aware the track at Bedford has a 101db noise limit and quite frankly my car would pass that without any form of silencing and thats with well over 300bhp and a GT Spec zorst(3.74inches). I think it's usually the cheap exhausts that make over 101db... oh yeah, and the nur spec..

Youre wrong

The drive by is 89db I think

We went to have a test the other week see the Bedford thread in the MS section for details

Apex single exhaust needed a bung and a decat silencer to pass, only just

**cHiL** · 13-02-2006, 08:38

Originally Posted by Mono Phil

Youre wrong

The drive by is 89db I think

We went to have a test the other week see the Bedford thread in the MS section for details

Apex single exhaust needed a bung and a decat silencer to pass, only just

I was looking here where they clearly state it's 101db.. Maybe they adjust their limits for different track days?

If it was 89db then thats not really worth doing as most people certainly on here would just fail even with a silencer..

**cHiL** · 13-02-2006, 08:41

Ah I see, the other test is measured 20 metres from the car....

**Jolly F** · 13-02-2006, 08:42

That is low, i need to sort this out early this year or i'll have problems...

**cHiL** · 13-02-2006, 08:50

Maybe you could bung up but increase boost made?.. Like for example when you close your exhaust opening you actually make it much more difficult to get boost but would increasing your settings bring the power back? It makes me wonder how big production cars manage with such low noise?..

**archenemy.co.uk** · 13-02-2006, 08:52

They have 2 ways of metering the noise, the static one is the 101 IIRC and the drive by, which is the important one is 89db. very difficult to fool this one all day, with 2 metering stations round the track and a no tolerance rule.

Thats why we took a trip up there - check it out now avoid dissapointment later. Me with Mongoose and sports cat breezed through

I remember passing you 2 up at castle combe (even though you did you best to hold me back and knock me off) Chil so its not too slow either

**cHiL** · 13-02-2006, 08:55

Look Phil. in principal I agree with the general message of what you have tried to say but making stupid accusations is not the thing to do and it's completely out of order. Do not accuse me of trying to "knock" someone "off" a track. That's wrong and certainly is not a joke!

**cHiL** · 13-02-2006, 08:57

Ecv Ecv Ecv Ecv!

**archenemy.co.uk** · 13-02-2006, 09:08

Blah Blah blah

**cHiL** · 13-02-2006, 09:17

um..

**archenemy.co.uk** · 13-02-2006, 09:22

dum de dum

Thread: Managing exhaust noise limits - teased from Japfest thread

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