exhaust Options for reducing noise levels

[Beau]

Hey guys,

Long story short, my exhaust system is shot! Rear section including Middle Muffler have both rusted and fallen away. I removed them this evening and turned the key, fair to say I reckon I need some sort of silencer as it just seems too loud. I'm going to test the DB's tomorrow and see if it's still within the law...

http://www.youtube.com/watch?v=uBlA_kAirwQ

I ideally want the cheapest way to reduce the noise, I don't mind the exhaust ending underneath the car, it's legal as I've seen it done on plenty of vans. I was thinking either a cheap silencer or some sort of Bung! Going to see if I can re use the rear muffler and weld it back on

What's everyone's thoughts?

 

[Shayne]

Can't see the rear muffler doing much at all it's too short to make a difference i reckon but if you can weld that back on then why not just go to a breakers and find something similar to the parts you removed .

 

[Beau]

Can't see the rear muffler doing much at all it's too short to make a difference i reckon but if you can weld that back on then why not just go to a breakers and find something similar to the parts you removed .

Ideally I'd rather improve the exhaust system rather than revert back. I can tell already that the turbo is spooling up more and the engine revs so much more freely. It sounds and feels very good. By adding in a similar muffler it'll revert back to normal and restrict the gases too much.

What I'm after is something that I can use to purely to reduce the noise created, so far bungs seem to be highly effective and relatively cheap.

 

[Shayne]

Just looking at bungs i don't think they are a good idea for a turbo diesel you want the gasses out as quickly as possible and i reckon they would cause a back pressure though i'm happy to be corrected . I can't see why a motorbike can wouldn't give you a straight through exhaust allowing the turbo to spool while at the same time making your truck quieter than standard . Its just a theory but performance bikes are far far louder than any diesel without an exhaust so possibly the silencers on bikes have better damping qualities .

First mod on every bike is to change the silencer and the oem one is worthless coz nobody wants it so you should get one cheap if you can find a matching diameter .

 

[Euan McGilp]

Fitted one of these http://www.roughtrax4x4.com/?doc=16&cid=1098&vid=1443 to my 95 - perfect fit, super quality, fast delivery, lighter & smaller than OEM and loads cheaper! Refitted std rear pipe (mine has no rear silencer) & now, 4 months on, sounds much better too!

Happy to recommend Roughtrax for this; fitted on original hangers & less restrictive than OEM.

 

[clivehorridge]

I don't understand the impression that silencers "offer resistance" to the exhaust.

The components in my silencer (and I saw them before they assembled it) are pipes of exactly the same diameter as the rest of the system. The only difference was they were perforated and surrounded in sound absorbing material. Thus sound bouncing off the inner wall of the tube would pass through the perforations and be absorbed, with a much reduced reflection where there were no perforations.

What would be offering the resistance in those circumstances? Just my understanding mind, ready to be educated!

 

[Shayne]

You have a custom made stainless exhaust Clive which is why its straight through , factory exhausts are often offset usually in the silencer not so much to offer resistance but to bounce sound waves back on one and other to reduce volume even before the absorbent material soaks it up further . The tone of your exhaust is instantly be altered by giving it a clear exit path and you can also change the note of it by adding or removing absorbent material . The droning sound at motorway speeds many worry about results from not having enough packing .

 

[Beau]

I don't understand the impression that silencers "offer resistance" to the exhaust.

The components in my silencer (and I saw them before they assembled it) are pipes of exactly the same diameter as the rest of the system. The only difference was they were perforated and surrounded in sound absorbing material. Thus sound bouncing off the inner wall of the tube would pass through the perforations and be absorbed, with a much reduced reflection where there were no perforations.

What would be offering the resistance in those circumstances? Just my understanding mind, ready to be educated!

Maybe I've misled you in my words... On the 90 series there are two main exhaust components. A big rectangle box which I believe is a muffler/silencer with baffles inside to absorb sound ect. Right at the end is a silencer as the one you've described. The main rectangle silencer I've described does affect performance unless it is a free flow silencer (most of these tend to be loud anyway).

Anyway as a temporary fix, I've welded on another piece so it points down from underneath the car exiting just below the drivers side step. I've also stuck piece steel wool inside and then a mesh over the end and this has reduced the loud turbo whine and burble.

http://www.youtube.com/watch?v=x6IGQTWUar0

I did a quick video of the sound, it's lower and according to my DB meter on my iphone it's just above 80db at idle.