[Es2] Who needs a 3 inch DP and exhaust?

[Dave Hord]

It's so variable I'm tempted not to answer...however, there are some tried and tested 'rules':

1) A cat will bring down the sound volume. The size, matrix type/design, and inlet/outlet cones determine how much. Never add a cat just for sound adjustment. 

2) A resonator is a very good idea for reducting sound volumes and/or resonations (drone). The problem being that the type of resonator, and where its placed will effect the changes to sound volume, pitch and resonation. Generally speaking, the further back in the system the resonator is, the better the volume reduction. 

In terms of volume, the A4/S's come in about 84db on the SAE test (number quoted from memory...could be wrong). The californian limit is 95db as tested using the SAE test. 95db is NOT that loud. Certainly not 'annoyingly loud'. 

The SAE test is done by measuing the sound as the engine is held at 80% of its peak horsepower RPM. So, if my car made peak hp at 10,000rpm, I'd do the test holding the car (in neutral) at 8000rpm. (You can do the math for your own vehicle). 

My rally project trips off 104db using the SAE test. I'd classify this as 'whoa, loud' but not quite the 'okay, that's just stupid loud' of 108db that we measured a friends '77 Chevelle at. The key is, however, that it hits 104db at 4400rpm. I'm typically not driving around at that level, I drive around 3000-3500 on the street where it produces a rather tame 86db. Its so quiet that I can't hear it when racing...and the car has no interior or insulation. In fact, I'm straight-piping it now for that reason. 

The annoying part about an exhaust is rarely its peak volume, but its volume while cruising. 

-Dave

-----Original Message-----
From: Ben Klumper <bklumper at mdbworld.com>
Date: Thu, 22 Jun 2006 13:40:49 
To:Dave Hord <dhord at rogers.blackberry.net>, es2-bounces at audifans.com,       Peter Schulz <pcschulz at comcast.net>, es2 at audifans.com
Subject: Re: [Es2] Who needs a 3 inch DP and exhaust?

So Dave would adding a cat bring the dB's down much? What if I were to add a 
center resonator?

Ben

> On a turbo system 3" should not be unbearibly loud at all. The turbo does 
> a whole lot for dampening out the noise volume.
>
> While I haven't experienced 034's system myself, 4.5 years of exhaust 
> design experience tells me their system should be be in the 'sporty' scale 
> of volume.
>
> On a 20vt, my estimate would be some-where between 92-96db by the SAE 
> test. That's a guess based entirely on the design, muffler used and some 
> experience. I could be way off.
>
> -Dave