Exhaust system of a turbo-charged engine

Abstract

An exhaust system of a turbo-charged engine includes an exhaust pipe connected to a turbo-charged engine, a front muffler, and a rear muffler disposed in the exhaust pipe in an order of the front muffler and the rear muffler in a direction of flow of exhaust gas. Each muffler of the front muffler and the rear muffler includes an inner pipe. The inner pipe extends straight and continuously from an inlet to an outlet of each muffler and is not throttled in diameter between the inlet and the outlet of each muffler. Each muffler does not include an enlarged chamber in each muffler. The front muffler includes a high-frequency resonance chamber outside the inner pipe. The rear muffler includes a high-frequency resonance chamber and a low-frequency resonance chamber outside the inner pipe.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an exhaust system of a turbo-charged engine, and more particularly, relates to a structure of a muffler thereof. [0003] 2. Background of the Invention [0004] The following two points are required for the exhaust system of a turbo-charged engine from a viewpoint of performance: 1) Low exhaust back pressure [0005] With the turbo-charged engine, due to its large amount of exhaust gas, a large capacity of a catalyst needs to be provided upstream of a muffler, so that an engine exhaust back pressure is likely to be high. In order to increase an engine output, the engine exhaust back pressure is required to be lowered. 2) Lowering a flow noise having a high-frequency [0006] With the turbo-charged engine, due to its large amount of exhaust gas and its high velocity of exhaust gas, a relatively large gas flow noise (a high-frequency noise) is generated, so that a subsidiary muffler 1 (a mu...

AI Technical Summary

Benefits of technology

[0012] An object of the present invention is to provide an exhaust system of a turbo-charged engine thereby obtaining a low exhaust pressure, decreasing a gas flow noise, and decreasing a muffler volume.

[0020] With the exhaust system of a turbo-charged engine according to item (1) above, since the inner pipe extends straight and is not throttled in diameter from the inlet to the outlet of the muffler, a pressure loss is small and the exhaust back pressure is very low. As a result, the output of the turbo-charged engine is improved to a great extent.

[0021] Further, since there is no enlarged chamber in the muffler, a flow turbulence which is generated at the inlet of the inner pipe from the enlarged chamber in the conventional muffler is unlikely to be generated, so that a gas flow noise is decreased.

[0022] Furthermore, since there is no enlarged chamber in the muffler, the volume of the muffler can be minimized by selecting a volume of the low-frequency resonance chamber as small as possible.

[0023] With the exhaust system of a turbo-charged engine according to item (2) above, since the front muffler includes a high-frequency resonance chamber outside the inner pipe of the front muffler, and the rear muffler includes a high-frequency resonance chamber and a low-frequency resonance chamber outside the inner pipe of the rear muffler, both a gas flow noise (i.e., a high-frequency noise) and a noise due to a columnar resonance at a deceleration time (i.e., a low-frequency noise) can be decreased.

Problems solved by technology

With the turbo-charged engine, due to its large amount of exhaust gas, a large capacity of a catalyst needs to be provided upstream of a muffler, so that an engine exhaust back pressure is likely to be high.

For example, though a muffler disclosed in Japanese Utility Model Publication HEI 6-25506 has a high-frequency resonance chamber, since an inner pipe 5 is throttled at an inlet of the muffler relative to an exhaust pipe, a pressure loss is generated at the throttled inlet and, as a result, the low exhaust back pressure required to the exhaust system of the turbo-charged engine cannot be obtained.

As a result, the following problems are likely to happen:

a) It is difficult to obtain a low exhaust back pressure

In the main muffler 2 having the enlarged chamber 3, since the exhaust gas flow passage has a U-turn portion and changes in cross-sectional area, a pressure loss is large so that it is difficult to obtain a low exhaust back pressure.

b) A gas flow noise (a high-frequency noise) is likely to be generated.

Particularly, at the inlet of the pipe 6a the gas flow is turbulent and generates a gas flow noise.

c) A volume of the muffler is large and a noise decreasing efficiency of the muffler is low.

This means that the volume of the conventional main muffler of the turbo-charged engine is unnecessarily large and the noise decreasing efficiency per a unit volume is low.

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