What do air silencers do? (Just curious)

kfa4303

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Sep 17, 2010
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Hi all. What do air/carb "silencers" do, and why some motors have them, while others don't. For example, I have a '63 10 HP QD2-22 with quite a large air silencer, whereas my '66 33hp does not have one at all. What is it that they "silence" exactly? Seems like silencing would need to occur at the exhuast end of things right? Just curious.
 

robert graham

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Apr 16, 2009
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Re: What do air silencers do? (Just curious)

They help silence the intake sound and help prevent engine fires from backfires through the carbs under certain conditions. That's about it as far as I know.
 

kfa4303

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Re: What do air silencers do? (Just curious)

Gotcha. Thanks Robert. I assume it needs to be kept as clean as possible so no debris gets sucked into the carb, right?
 

Mark42

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Re: What do air silencers do? (Just curious)

Robert is correct, they silence the roar that comes out the carbs. Can get pretty nasty at WOT.

All the motors I am familiar with have them, even if just a simple 180* bend like the Force to a more complex baffled system like my Johnsons have.
 

boobie

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Re: What do air silencers do? (Just curious)

On certain mtrs if they are not installed properly the mtr will not run at wot and sometimes at mid range.
 

F_R

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Re: What do air silencers do? (Just curious)

The reed valves on two-stroke motors can make a lot of noise as they open and slap shut. The silencer muffles it. Your 33 does not have one because the fiberglass hood is the silencer. It also has a silencer pad where the air enters the lower cover (pan). Yeah, yeah, I know, the 10 has a fiberglass hood too. It took the engineers a couple of years to figure out the sound control without a silencer (saves money).

On more sofisticated motors with exhaust tuning, the silencer is part of the tuning, sound waves actually acting as a sort of supercharger. That is why some motors suffer a performance loss without the silencer.

Not only that, the airflow through the silencer figures into the fuel/air mixture which is controlled by fixed carburetor jets. Upset the air volume without compensating with jet size and you upset the mixture.
 
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