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Exhaust lagging


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I want to beef up the lagging of my exhaust system in particular the hospital silencer.  I know you can get rolls of 25mm lagging but ASAP eg only seem to sell it in minimum 7m lengths. I'll hunt around the boatyards if need be but does anyone know if/where you could get a short length of this stuff?    

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10 minutes ago, Neil2 said:

I want to beef up the lagging of my exhaust system in particular the hospital silencer.  I know you can get rolls of 25mm lagging but ASAP eg only seem to sell it in minimum 7m lengths. I'll hunt around the boatyards if need be but does anyone know if/where you could get a short length of this stuff?    

Hospital silencers are usually pretty fat. 7 mx25mm might not be enough by the time you've done the half width overlap.

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2 hours ago, bizzard said:

Hospital silencers are usually pretty fat. 7 mx25mm might not be enough by the time you've done the half width overlap.

It's 25mm thick - and either 300mm or 600mm wide, IIRC.  A roll of this stuff costs about £500.  Obviously aimed at big seafaring boats but the 600mm would just fit snugly around my big silencer between the supports.  I think I may have to trawl (sorry) round the bigger boatyards to find an offcut.      

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1 hour ago, smileypete said:

Why the need to wrap the silencer itself?

Bukh engines are notorious for smoking especially when lightly loaded, one of the reasons being the low exhaust temperature, the fumes just don't get burned off.  I reckon that by insulating the entire exhaust from the manifold will help to raise the temperature and reduce the smoke.   I don't think it's a bad idea to reduce the heat dissipated in the engine room either. 

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Tony Brook is da man for engines.

But what colour is the smoke? That can help diagnose the problem.

I'm no expert but would have thought lagging the silencer would make little difference to engine smoke, apart from making it a little warmer. :)  I doubt anything would 'burn' as such in the exhaust unless there's a catalytic converter.

 

Edited by smileypete
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On 2017-5-27 at 19:14, Neil2 said:

Bukh engines are notorious for smoking especially when lightly loaded, one of the reasons being the low exhaust temperature, the fumes just don't get burned off.  I reckon that by insulating the entire exhaust from the manifold will help to raise the temperature and reduce the smoke.   I don't think it's a bad idea to reduce the heat dissipated in the engine room either. 

By the time the gasses get to the silencer they will probably be too cool to burn any smoke, so insulating it will make little difference to smoke.  I do know that exhaust gasses can be more corrosive the hotter they are, but you do want the silencer hot enough to avoid condensation internally as that is also corrosive.  It is also my understanding that the hotter the exhaust gasses are the more noise the exhaust will make, so it will be interesting to see if lagging your silencer gives an overall improvement in smoke, noise and silencer life.

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