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Hi all, I've been looking at getting a side exit exhaust but I don't want to throw more money away on the bloody landy!! I recently fitted a straight through centre section and have a de-cat down pipe but the resonator on the back still appears to dampen the sound. Is it okay to just remove the rear section (it seems pretty far back already) or is it likely to fill up my cab with smoke and carbon monoxide? I've got a 300TDi 90.

Cheers,

mr_mcp

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Hi all, I've been looking at getting a side exit exhaust but I don't want to throw more money away on the bloody landy!! I recently fitted a straight through centre section and have a de-cat down pipe but the resonator on the back still appears to dampen the sound. Is it okay to just remove the rear section (it seems pretty far back already) or is it likely to fill up my cab with smoke and carbon monoxide? I've got a 300TDi 90.

Cheers,

mr_mcp

Whats the main driver for having a side exhaust? to get it out the way for better axle articulation? - or you like the noise? I seem to be doing everything possible to make mine quieter...?

Dont quote me but, you have to bare in mind that engines are designed with a certain back pressure, changing the exhaust config too much could change somthing so its noticable?

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Dont quote me but, you have to bare in mind that engines are designed with a certain back pressure, changing the exhaust config too much could change somthing so its noticable?

There you are quoted for posterity if your wrong!

Um... I think its only petrol engines where back pressure matters.

But I could be wrong. :unsure:

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My rear section of exhaust worked itself off [good old rust!] a while back, and I ran it like that for a few days. The cab often ended up stinking of exhaust fumes, as did my lungs I imagine. I wouldn't recommend it too much

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Ok I've just thought about this and i came to the conclusion:

All 4 stroke engines (not considering a turbo just now) need to expel exhaust gas, to make it the most efficient process, the engine doesn't want to have to work to expel that gas - which is directly related to back pressure of the exhaust system, ideally you want no back pressure or even a little bit of negative pressure, allowing the exhaust gas to exit the cylinder with least effort.

Now most Diesel now have a turbo fixed on the outlet of the exhaust system. for the hot side (turbine) of the turbo to spin up it needs a specific pressure difference across the hot side inlet and outlet.

Now if you made the exhaust longer (effect of increasing the back pressure) then if the turbo was started by the pressure drop across the hot side it would need more pressure on the inlet, meaning the engine would have to work to pump it up. Not what you want, if you shortened the pipe (reduce back pressure) then the turbo would spin up with less inlet pressure from the cylinder exhaust. thats if the turbo was controlled by the pressure across its outlet, I have to check how Auto ones are controlled.

So... shortening your exhaust wont do it any harm.

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All 4 stroke engines (not considering a turbo just now) need to expel exhaust gas, to make it the most efficient process, the engine doesn't want to have to work to expel that gas - which is directly related to back pressure of the exhaust system, ideally you want no back pressure or even a little bit of negative pressure, allowing the exhaust gas to exit the cylinder with least effort.

Google 'internal combustion Exhaust Tuning' and 'internal combustion exhaust gas extraction' and 'pulse tuning internal combustion exhaust manifolds systems', you will see how the above is not really that simple :)

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Google 'internal combustion Exhaust Tuning' and 'internal combustion exhaust gas extraction' and 'pulse tuning internal combustion exhaust manifolds systems', you will see how the above is not really that simple :)

Bah, it is ;) - for your average jo - 100k, rattly engine.

I just found this website that describes turbine operation/control quite well.

http://www.turbodriven.com/en/turbofacts/designControlSystem.aspx

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Hi all, I've been looking at getting a side exit exhaust but I don't want to throw more money away on the bloody landy!! I recently fitted a straight through centre section and have a de-cat down pipe but the resonator on the back still appears to dampen the sound. Is it okay to just remove the rear section (it seems pretty far back already) or is it likely to fill up my cab with smoke and carbon monoxide? I've got a 300TDi 90.

Cheers,

mr_mcp

Hi, when I got my Landy 1987 90 with a Disco 200TDi, it already had a nasty six inch square hole behind the rear wheel and an old rusty pipe sticking out,and the exhaust ran through the passenger footwell and was boxed in to such an extent the passenger could only put one foot on the floor, I have since repaired both the holes and it now exits symetrically of the fuel filler cap on the passenger side, I have added a chrome curved round tip to direct the smell backwards, it works great, no silencers at all, sounds sweeeeet :D get some looks, when im out and about. The good thing is that it is still road legal and has an M.O.T. with the exhaust like this, as long as it is I beleive below 85dB (about the noise a mechanical road breaker makes) and doesn't stick out to the extent that you turn it into a roman chariot and slice people in half as you pass them (couple of inches) then all is well with the Feds. As for cost we went to the local scrap yard and bought a transit van exhaust for £20.00 and made it ourselves, if you call in to kwik fit and similar places they will happily give you pipes that they have taken off cars and vans for free, I would stick with Transit type pipe as its a similar bore.

Cheers Paul

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I just had to replace my exhaust, I had the two mufflers taken off (ruuuusty!) and they were replaced by a single centre muffler. The result was quiet amazing, the 2.5 n/a is not exactly a power house but I now have much more mid-range pull and when climbing hills I am not constantly having to find 3rd.

BTW my exhaust exits at the back, I also could see no reason to do a side exit unless you want exreme articulation.

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The main reason I'd like a side-exit is purely down to aesthetics, I do however want to remove/replace the rear section to make it sound louder and any performance gain is more than welcome :D

Sounds like I might smoke myself out by taking it off... hmmm maybe I'll give it a try & see?

Thanks all for the comments, mr_mcp

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on a 300tdi the rear section is so restrictive, it's worth replacing it with straight pipe and a 90 degree bend. I t gave my 980 a whole 4mph more power uphill.

I have the standard centre box and just a simple rear end with a 90 degree bend.

Next to remove all silencers and fit a tiny 110 back box in the middle.

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most of the /\/\/\/\

in the nicest possible way - :P - pish.

the turbo damps the vast majority of the noise coming from the engine and is easily the most restrictive bit of the whole system. Its meant to be restrictive or it wouldnt convert the exhaust gas energy into turning the blades to create pressure in the inlet manifold!

So yes, you can remove all the boxes and cat and not get completely deafened. Mine runs like this. Yes it is noisier than a standard system, yes there is a certain rev band where it 'booms' a little bit, but thats jsut the resonance frequency from the length of my pipe. it is live-able with and i;m happy to trundle up and down the motorway etc without discomfort, having black sabbath on at 120Db is my usual problem, not the exhaust noise.

and yes:-

you do not need back pressure in a turbo diesel exhaust system AFTER the turbo itself. Pulse theory and all that stuff still applies before the turbo, but the less back pressure you have after the turbo the better.

The turbine spools up on the pressure differential between the manifold and exhaust side of the turbine. The greater the pressure differential the faster it spools up. If you have a restrictive exhaust pipe, then the engine has to produce more pressure at the manifold side (higher revs/throttle) to create that same pressure differential to get it spooled up.

If you dont believe me, ask anyone whos reversed into a bank and blocked the tailpipe with mud, or bent their exhaust pipe offroad and ask what happened! or alternatively ask someone who runs no cat or boxes if their turbo spins up to pressure quicker with less lag and lower revs.(YES IT DOES!)

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I had no silencers on my 200Tdi 90 for a while for various reasons and the noise drove me nuts.

Far too noisey for my tastes, and the whine from the turbo was horrid.

Back on a standard system for now, but will convert to a side-exit above and behind the rear wheel in the future. Reason being to improve the clearance off-road, already bent it once and filled it with mud another time. If the rear silencer box has to go as a result then so be it, but the centre one will stay :)

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Replaced the centre silencer on my 200tdi 110 with a straight through pipe - absolutely no difference to noise level! Rear resonator about to rust off, will see if that makes any differece...

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People die every year from carbon monoxide poisoning when the drive off the road and end up in a snowbank but keep the engine running for heat without digging out the exhaust.

Side exit is fine, just get the fumes away from the undercarriage.

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