As posted some days ago I played a bit with a reflective damper. The result in terms of noise is so good that I plan to make a proper one and, if finances allow, to test on an engine bench versus a straight through design.

Have attached a picture of what I am planning. According to alibre the total weight should be 5kg in RVS. But I've used rather thin materials so I don't know if that will stand.

Am interested in any form of feedback on this.

For instance; I chose a side exit in order to use the space normaly used by the exit-bend as extra room to dampen the noise. Will this look ok on a seven?

Rgrds,

Mies.
Rescued attachment Exhaust total assembly 2.jpg

Hi having already done silencers in a simalar fashion to that desighn.

It dose make for a quieter sound but on a 200bhp zetec it robs it of 10bhp minimum.

cheersw matt

an interesting project.Are the green tubes really staggered in length,if so why? and is there any packing in the exhaust

Whilst it may quieten it down a lot, I can see that robbing loads of power. Might be worth it if you're struggling to get on a track due to noise though, as running with less power is better than not at all.

Hi Matt, thanks. Question; the 10bhp you mention should be the same on my 200+ audi. Is this measured or assumed? Reason I am asking is that I don't want to spend money on having it tested when it has been done before.

The total square througput to the next chamber is always higher than the 60mm diameter intake. And in line with a reply to my earlier posting; the first chamber is bigger than 2 litre. I was hoping this would limit powerloss

On the other side; if it stays within 10bhp I will be happy. The added comfort on long trips is worth more to me.

On the other replies:

- There is no packing planned. The idea started because I got tired of the continuously repacking of my exhaust. Having said that I am thinking about putting in a 20 lenght chamber that is packed. In order to maximise the sound absorbsion I was thinking of using 6 small diameter perforated pipes in stead of 1 big one. Any comments on this? Will this be effective. I know it will be a mess to pack...)

And yes the pipes you see are staggered. There is no facts behind this except the advice from a guy designing motorbike aftermarket exhausts. He told me that the lenght of these small pipes influence the type of sound it generates. He told me that it simply has to be tested and cannot be predicted. He also told me that you should always use different lenghts where possible to maximise the damping coverage.

Again I have no facts behind it so please let me have your experience!

Hi yes it is better to be able to run but with less power.

But what if you could run with the quieter silencer and no loss of power win win situation.

cheers matt

Hi i the 10bhp loss was on an actual car on rolling road test. But your deighn is obviously a little bit different but i would assume that it would be roughly the same loss but only one way to tell.

As said above though people would be prepared to run on trackdays with a loss of power if it meant they could acctually get on circuit.

But the racers will not accept any loss in power but we are only having to get down to 105 db not as low as some of the circuits require for trackdays which is 98db generaly.

cheers matt

After re reading your last post it sounds like you heading in the same direction as our thinking Ie looking at what the bike manufacturers do. as they are far more advanced than the car industry whith silencers.

[Edited on 10/2/07 by procomp]

Asd I've said elsewhere, I'd be happy to accept a small loss of power in place of a distinctly anti-social straight-through exhaust that's still noisy even though recently re-packed. I like a rousing exhaust note - but not so much that I'm embarrassed!

David

Hi sorry david hope you did not think i was having a pop but was trying to say that it is possible to get the noise down with no loss of power.

But it dose make your wallet lighter. Which is a good thing for the bec guys.

cheers matt

On the sound thing. The quietter exhaust has had another plus. I can now hear the intake sound of the four throttle bodies. Today I actually took off the airbox. I know it cost me some power (intake air was 4 degrees hotter) but I really LOVE that sound...

I simply kept on slowing down and hit the trottle again...:-)))

Rgrds,

Mies.

hmmmm, fluids don't like sharp chanes in direction - the side exit and pipe thingies fore the air to go trouh 90 degrees - not good for happy air;

can you put them in at an angle yet still retain the side exit? shouldn;t affect noise much but will rob you of less power (or not - dunno much about these things)

Why not re-design the whole exhaust system, who say it has to go out the side?

Get rid of the noise and the fumes!!!

Hi JohnMor; How did you route the exhaust; via the sides or via the tunnel?

I took the exhaust from the V6 joined in an of-set oval box in the tunnel and than spilt again into two boxes below the fuel tank.

I still have around 4" clearence.
I made the original system from mild steel and used old exhaust boxes to see if it was practical.
I will attempt a new stainless system this year.

quote:

---

Originally posted by procomp
Hi sorry david hope you did not think i was having a pop

---

Hi for rear exit systems the westfield V8 was quite good but required a slightley higher ride height. What sort of use is the car being used for ROAD / TRACK or both.

cheers matt

Hi.

The first cans I ever made were copies for my ZX10 bike.

They were a multi chamber design like yours but by clever use of the pipes inside
the gases entered expansion chamber 1, then into 2, from 2 into 4 through tubes,
back to 3, and from 3 through a tube to exit the rear.

The gases traveled 1000mm in a can only 600mm long, and length is more
important than diameter as far as sound is concerned.


Paul G