When an exhaust system is removed the engine is so loud. so if the motor is naturally that noisy, how does the muffler make it so quiet?
In: Engineering
The muffler has chambers and baffles inside it that allow the exhaust to expand and come out of the tailpipe at a lower velocity than it would out of a straight header without a muffler. Those baffles are engineered to do multiple things. Some mufflers are very quiet, others produce a certain kind of sound, others produce a good bit of engine power due to the way the exhaust flows.
An engine works by igniting a small amount of fuel inside a piston, so every time this happens there is a blast of pressurised air out of the exhaust side of the engine.
Without any exhaust system attached, that little blast of air is coming straight out the side. So standing near the engine we hear all of these blasts of air as a loud noise.
When we install an exhaust system, instead of these blast of exhaust air heading straight from the engine to our ears, they are directed down the exhaust system instead. Inside the muffler of the exhaust system there are lots of small baffles that catch and bounce this air back and forth a bit, which also happens every time there is a bend or change in the tubing. What this does is cause the air to slow down and mix about, so rather than having a short, distinct blast of air from every engine cylinder separately coming directly to our ears, we get all of these blasts of air slowed down and mixed together, which means a much lower volume.
The downside to slowing down the air coming out of the engine is that the engine generally works best when the air is allowed to escape quickly. So you will find sports cars often have louder exhausts that help the engine create more power, while family cars that don’t really need much power will trade some of that for a lower volume that is more comfortable for passengers and bystanders
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