How An Exhaust System Works? Part B

From this rear oxygen sensor, we come along the pipe and we hit the first of our two mufflers or silences on this Exhaust system.

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So the purpose of these mufflers is to shape and generally to reduce the amount of noise coming off the vehicle produced by the exhaust. And in that subject, a very tight regulations, there is very specific rules on how much noise an engine, a vehicle, an exhaust system can produce and so the silencers here have the task of bringing the noise level down.

If you have ever heard an exhaust without a silencer on it, you will know it is incredibly loud. It is immediately apparent if there is no muffler, no silencer on an exhaust. So they not only reduce the noise, but they also shape it. So manufacturers know that the sound of an exhaust sells vehicles. It sounds good. And particularly on this vehicle, Mazda, with the MX5, starting with the MK1, they knew that a good sporty sounding exhaust would give this car more of a sporty feel, make it more of an enjoyable driving experience, particularly when you have got the top down on a cabriolet, you have more connected with the exhaust sound of the vehicle.

So Mazda made an effort. This is more of a resonator, it shapes the exhaust note as it works its way through the system, whereas this rear silencer here has a meat of the silencing in it. It is obviously much bigger and it has a more of an absorption, more of an effect on reducing the noise of the exhaust system. We will talk about both of these silencers later. We will chop them open and see actually what is inside them and how they work.

Now, coming off this rear silencer, we have the tailpipe. And the tailpipe just really has the job of taking the exhaust gasses from the final silencer out to the rear of the vehicle to vent out to the atmosphere. And something to note is the tip of our tailpipe here has a nice, kind of chrome stainless effect, it is quite a stylish, polished finish.

Because really, you know, that is the only part of the exhaust system that you actually see when you look at the vehicle. And of course as you see this chrome pipe, it gives the impression that the rest of the exhaust system is actually a beautiful, polished chrome, stainless steel, when in fact, most of exhaust systems are made from a mild steel with a little bit of galvanizing on them. All exhaust system are of a sectional design, which means they are made up in chunks or parts. So on this system, we have the header coming down and we have the front pipe, which might be called the down pipe, that comes along.

We have the mid pipe. We have rear pipe there. And they are bolted together by exhaust flanges. So each section has a flange and those are bolted together to join the system. In between the joints is a gasket, shaped around the actual flange itself. But on this particular joint here, we have a kind of pressed gasket here, a sheet metal type design that fits into there and on these other, later joints, we have a round, circular gasket which is made of a kind of heat resistant material which is compressed when the sections are bolted together.

In terms of fitting an exhaust to a vehicle, not only does it come in this sectional design, but it needs to be isolated from the bodywork of the vehicle. So when we talked about the engine mount, we discussed that the engine vibrates, creates a lot of vibration, which we do not want to transfer into the rest of the vehicle. So the engine is mounted on rubber blocks and the exhaust is bolted directly, it is a rigid fitting to the engine. So if the exhaust was then bolted directly to the bodywork of the car, you would have made the engine mounts completely pointless.

We would have made them totally ineffective by joining the engine through a rigid exhaust to the bodywork. So exhaust systems will tend to hang on rubber hangers. We have got some at the rear here. They hang on these rubber mounts which isolate the exhaust from the bodywork and stop the vibration from the engine being carried into the actual vehicle itself. Now there is different types. Every manufacturer has a different type of rubber exhaust mount. I do not know why they cannot standardize on one particular design but every manufacturer has a different exhaust mount design.

( To be continued...)