【Exhaust parts】 Technical terminology introduction series! ~ Muffler ~

Have you ever heard a jargon that you haven’t heard before when purchasing used engines and used auto parts from suppliers?

This time, we will introduce some technical terminology unique in this industry.

Please take a look, may be useful when purchasing used engines and used auto parts.


What is muffler?

An automobile’s muffler absorbs and quiets the sound of explosions caused by the combustion of the engine. If the exhaust gas is discharged directly into the air without passing through the muffler, it will expand all at once due to the temperature difference, causing the air to vibrate and thus produce a loud noise.

Another feature of mufflers is the purification of exhaust gases.
The gases emitted from the engine content harmful substances that can cause major environmental pollution if exhausted as is, so the muffler plays a role in making the harmful substances in the exhaust gases as harmless as possible. For this reason, mufflers are required by law in Japan, and must be installed when driving on public roads.

Muffler parts

Exhaust manifold

The exhaust manifold is the connection between the engine and the muffler, and is the part of the muffler that is closest to the engine. Therefore, when an engine is produced as a used part, the exhaust manifold is often removed as part of the engine.

If the engine is produced without the exhaust manifold, there is a high possibility that moisture and dust will enter through the connecting parts after production.

At Kaiho Industry, we do not sell exhaust manifolds individually, but we sell them as a set with the engine.
The exhaust manifold collects exhaust gas from each cylinder and feeds it into the catalyst. It is made of sturdy steel to handle the high heat of the gasoline engine exhaust.

Exhaust manifold

O2 sensor

The O2 sensor is installed in the front pipe between the exhaust manifold and the catalyst.

The O2 sensor is responsible of detecting the oxygen concentration in the exhaust gases coming out from the engine, and measures whether the engine is burning efficiently or not. If there is any abnormality, the engine lamp on the monitor will light up immediately.

When we produce mufflers at Kaiho Industry, we keep the function of the O2 sensor intact.

O2 sensor


The exhaust gas from gasoline engines contains many harmful substances, and automobiles use catalysts to purify those substances.

Toxic substances are decomposed by chemical reaction with rare metals (mainly platinum [Pt] and palladium [Pd]) in the catalyst) and a cleaner gas is emitted into the atmosphere.

The percentage of rare metals in the catalyst varies depending on the year of manufacture, and the value of the catalyst varies accordingly.

At Kaiho Industry, we do not export or sell catalysts except for CKD purchases.


Rear muffler

The rear muffler, also known as the “tycoon”, has a sound deadening function. Since it is formed of iron, it is prone to deterioration caused by winter snow plows and years of use. Once rust or a hole is made in the rear muffler, noise will be produced every time the engine is started.

Each muffler manufacturer has developed a variety of mufflers to diminish the noise but still produce a pleasant sound, and various external mufflers are also popular.

rear muffler

Introducing additional services exclusive in Kaiho Industry!

At Kaiho Industry, we produce mufflers on a custom-made basis.
For example, if a customer wants a muffler without a catalyst, we can sell the muffler and pipe without the catalyst.

Also, since used parts mufflers are subject to deterioration due to rust, our experienced staff carefully checks the condition of each muffler upon dismantling before selling them.

Please feel free to contact us first. We will respond in good faith.

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