Why do Exhausts sound like they do?

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Silencers or mufflers are necessary on gasoline and Diesel engines to silence the sound made when each one of the exhaust valves open. When an exhaust valve opens, it opens very suddenly and lets a large pressure pulse escape from the engine cylinder and that pulse travels down the exhaust manifold towards the tailpipe. When that pressure pulse finally escapes, it creates a large sound wave. you can think of the process of an exhaust valve opening to be similar to what happens when a balloon pops. If exhaust valves opened very slowly, or if the pressure in the cylinder was nearly atmospheric at the time the valve opened, we would not need silencers on the exhaust, but the engine wouldn’t operate as well.
An exception would be an Atkinson engine running at low-to-moderate power levels, because a properly set-up real Atkinson engine nearly fully-expands the gas in the cylinder at the end of the power stroke.

Changing camshafts will change the exhaust sound. While performance cams do usually affect combustion qualitt, the real reason for the sound change is that when you change the camshaft you are changing how quickly the exhaust valve opens and what pressure the sound pulse starts with, so you are directly changing the character of the “pops” that form the exhaust sound you hear at the tailpipe.

• This topic was modified 5 years, 11 months ago by admin.

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