Professors often recommend some cars that are worth buying, and we sometimes mention that a car uses a double exhaust manifold in the evaluation of these cars. Everybody is on the road, also really see some car exhaust pipe layout form is different, some only one-sided single root, some are unilateral two, and there are both sides have exhaust pipe. However, have you ever thought about the layout and number of the exhaust pipes in different forms, in addition to the appearance of the impact, in the end what is the actual role?

We have to see what the exhaust system of the car looks like. Pictured above is the decomposition map of the automotive exhaust system, the front end is the catalytic converter, now every car to some things, and then in the catalytic converter before, is the car engine exhaust manifold, exhaust gas from the cylinder, we must first pass the exhaust manifold. Okay, let's go back and look at the big yellow object in the middle, the front muffler, and it's probably somewhere in the middle of the car. The work of this thing is the first time, after the first sound is finished, the exhaust gas will enter the rear silencer to further silence, and finally discharge the atmosphere.

So the exhaust pipe on the one side or on both sides, the impact on the car is noise. The exhaust noise of the double side exhaust pipe is lower than that of the single side exhaust pipe at high speed. And the single side double exhaust pipe, compared to the single exhaust pipe at low speed noise can also be reduced. So, why is that?

Frictional noise and dynamic noise

Everyone knows that the exhaust system makes noise, but how does this noise come from? Exhaust system noise is divided into two kinds, friction noise and dynamic noise. Dynamic noise is the energy that the exhaust air carries itself, causing the sound of its own vibration. Friction noise is the sound produced by the exhaust air in the pipeline with different widths inside the exhaust system, the friction between the airflow and exhaust system, the sound produced by the exhaust system itself, and so on.

The dynamic noise doesn't change very much, but the friction noise increases with the engine speed. So, in fact, reducing the friction noise is the key point of the whole exhaust system noise elimination. How do you do that? Or look back at the top of the map, you may have noticed that after the first stage muffler out, double exhaust pipe, will be more than the exhaust pipe out of a single rear muffler, this impact on the large. More than one rear muffler, low speed noise will not have much impact, but the high speed noise, double out will be 2-7 dB lower than the single out. Not much? In fact, a lot has been true.

What's the difference between a double row of trachea or a big point in the exhaust pipe? This is the main impact of low speed noise, the truth is very simple, think about the same flow of water through two pipes, a narrow one thick, thick that root, sure that the water flow will be smaller than the narrow bar? That's the reason. One So I just want to double out the 4 exhaust is not good enough?