Straight through Exhaust Question

has anyone made an exhaust using the soot box (diesel cat) only as a silencer and was it noisy or made it quieter or no difference
Thanks

Noisy or quieter compared to what?

300bhp/ton said:

Noisy or quieter compared to what?

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Meant was it still very noisy or did the soot box dull the sound a bit rather than an open pipe

Wouldn't know, I can't hear the exhaust for all the other rumbles, whines, clunks and clanks

Answered my own question
Took the exhuast system off after the cat an it sounded as quiet as it was with the whole system intact.
Then took the cat off and emptied it, inside was full of ceramic fluting and mesh, now have empty cat back on and still quiet but a nice rumble down the pipes.

landowner said:

has anyone made an exhaust using the soot box (diesel cat) only as a silencer and was it noisy or made it quieter or no difference
Thanks

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I had a temporary exhaust set up while doing some various bits to my 300tdi 90 and at one point I only had a single silencer, that was a droning racket, I hated it. I cannot understand these little dweebs who go about with baseball caps and noisy exhausts, their cars must just be a nightmare on a long run.

As far as I can tell it made no difference to performance. Only performance improvement I ever felt was de-cating my 300tdi Disco when I fitted a brand new exhaust from manifold back, but still had all the silencers.

discomania said:

I cannot understand these little dweebs who go about with baseball caps and noisy exhausts,

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Wide exhausts, narrow minds.

landowner said:

Answered my own question
Took the exhuast system off after the cat an it sounded as quiet as it was with the whole system intact.
Then took the cat off and emptied it, inside was full of ceramic fluting and mesh, now have empty cat back on and still quiet but a nice rumble down the pipes.

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So are you saying you removed the innards of the cat, effectively, de-catting the system. If so, you might have a problem at the next mot.

Col

Colthebrummie said:

So are you saying you removed the innards of the cat, effectively, de-catting the system. If so, you might have a problem at the next mot.

Col

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Depends what engine he has, even so, the cat was knackered so not doing a thing anyway. MoT for diesels only really looks at the particulate. Not the type. Cat was for oxides, NOx etc.

Colthebrummie said:

So are you saying you removed the innards of the cat, effectively, de-catting the system. If so, you might have a problem at the next mot.

Col

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I called it a CAT because it was easier to type then diesel soot collector, it's 2.5 diesel and the exhaust is very clean, not much soot in box when I gutted it. It's only there to stop black soot on hard acceleration etc but mine doesn't smoke at all except a bit when starting from cold if I dont use the heater plugs.
And anyway, how are they going to reach the exhaust pipes to test at 2 metres high

discomania said:

I had a temporary exhaust set up while doing some various bits to my 300tdi 90 and at one point I only had a single silencer, that was a droning racket, I hated it. I cannot understand these little dweebs who go about with baseball caps and noisy exhausts, their cars must just be a nightmare on a long run.

As far as I can tell it made no difference to performance. Only performance improvement I ever felt was de-cating my 300tdi Disco when I fitted a brand new exhaust from manifold back, but still had all the silencers.

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That's not quite true I'm afraid. On a turbo diesel any silencers in the exhaust system are restrictive, the more open and free flowing an exhaust is on a turbo diesel motor, the faster the turbo spools up an the quicker your throttle response is.

I have a pre cat td5 defender, and I removed the center box and run it with just the small rear muffler attached, it is drony, but the improved torque at very low revs is incredible!
I did save my centre silencer box incase I found it too loud, and drilled out the studs and replaced with stainless bolts, I put it back on after being wound up by the reverberations (quite bad in a van sided 90, much more so than my brothers 110), but after stalling and having to d rop gears with a full load and heavy trailer, I reverted back to t he straight through, you really can tell a big difference. Its also improved economy to when not towing etc, probably just loud on a normally aspirated motor though

I have found that if you put two back boxes in then it will be very quiet, One at front and one at back, both straight through mufflers, one takes out the low sound (front) and the other removes the high sounds (back)so best of both worlds. used to experiment with scrap bits of exhausts on old cars I had.

Gottschalk said:

That's not quite true I'm afraid. On a turbo diesel any silencers in the exhaust system are restrictive, the more open and free flowing an exhaust is on a turbo diesel motor, the faster the turbo spools up an the quicker your throttle response is.

I have a pre cat td5 defender, and I removed the center box and run it with just the small rear muffler attached, it is drony, but the improved torque at very low revs is incredible!
I did save my centre silencer box incase I found it too loud, and drilled out the studs and replaced with stainless bolts, I put it back on after being wound up by the reverberations (quite bad in a van sided 90, much more so than my brothers 110), but after stalling and having to d rop gears with a full load and heavy trailer, I reverted back to t he straight through, you really can tell a big difference. Its also improved economy to when not towing etc, probably just loud on a normally aspirated motor though

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Read my words again and report back.

discomania said:

Read my words again and report back.

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Sorry I presumed you were referring to Landy drivers with straight thru's.

300 tdi would still benefit performance wise having a straight through, whether or not that outways the horrendous noise increase is debatable, most certainly not. Sorry I wasnt meaning to be a dîck, just that on turbo motors (like our landys) all the big tuning companies do offer straight through, free flowing exhaust s as performance gainers, I was just pointing it out is all, not necessarily "wide exhausts, narrow minds" as was stated before.

I quite like the sound of a big bore exhaust, especially on a v8...

discomania said:

I had a temporary exhaust set up while doing some various bits to my 300tdi 90 and at one point I only had a single silencer, that was a droning racket, I hated it. I cannot understand these little dweebs who go about with baseball caps and noisy exhausts, their cars must just be a nightmare on a long run.

As far as I can tell it made no difference to performance. Only performance improvement I ever felt was de-cating my 300tdi Disco when I fitted a brand new exhaust from manifold back, but still had all the silencers.

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I was directly stating that as far as I could tell, and by tell I would suggest what I could feel, having the setup described above made no difference to my 90. It was just noisy. However a de-cat, and read, remove a blocked up box of soot, on my 300tdi Disco did make a improvement I could feel.

My point was only that removing a silencer and leaving one, as far as I could tell, made no difference. If you cannot feel it, or see it in fuel savings then it is not worth the effort in my eyes.

Gottschalk said:

Sorry I presumed you were referring to Landy drivers with straight thru's.

300 tdi would still benefit performance wise having a straight through, whether or not that outways the horrendous noise increase is debatable, most certainly not. Sorry I wasnt meaning to be a dîck, just that on turbo motors (like our landys) all the big tuning companies do offer straight through, free flowing exhaust s as performance gainers, I was just pointing it out is all, not necessarily "wide exhausts, narrow minds" as was stated before.

I quite like the sound of a big bore exhaust, especially on a v8...

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I get your post, that's why I said read it again, as I was discussing only 2 very specific situations and the result of each, not a general blanket comment. It all good. I fairly well versed in the benefits of big bore and or straight through exhausts, it's the most simple principles of gas kinetics, but I like the quiet. A noisy exhaust from an engine that actually sounds good is fine for off-road or farm use or car shows or the race track but if it drives on public highways I want it to be quiet.

I like to drive listening to a nice exhaust note, that's why I rerouted the landy pipe to exit on drivers side, not loud, just a nice sound.