Water Lift Silencers
More sophisticated than the in line muffler is the vertical lift silencer. These are also referred to as 'water lift' or 'water-trap' silencers. This type of silencer can be positioned well below the waterline, allowing the exhaust run from the engine to have a nice, safe, steep angle. You might think that such a device would rapidly fill with water and eventually block the exhaust completely, but this doesn't happen. In a correctly designed unit, the water level stabilises in the bottom of the chamber, just level with the bottom of the outlet pipe, with pure gas swirling around above it. Water is picked up by the gas on the way out and this further silences and cools the flow. Waterlift silencers should reduce exhaust noise by about 40%, compared with an unsilenced system.

Dual chamber waterlift silencers are even more effective. The two chambers, one above the other, force the gas and water to separate and remix twice, often leading to a total noise reduction in the region of 70%. Naturally, they are more expensive than the single chamber variety.

Waterlift silencers come in all shapes and sizes. Most common is the vertical cylinder variety, which can have top inlets, horizontal or angled side inlets and a wide variety of outlets. However, horizontal lift silencers are also available, and you can get either type with dual inlet stubs for use with vee configuration engines. The variations are endless, but the important thing is that the

internal design should be efficient and the silencer be chosen to exactly match the requirements of the engine and the rest of the exhaust system. This is not a D[Y job: please seek the advice of your supplier from the word go!
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Silencers continued...