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Exhaust system design, what is useful for a pilot to know?

We have already discussed that many unjustifiably consider the exhaust system to be the only merit of the exhaust sound. However, advanced motorcyclists are aware that a properly sized exhaust system can improve engine performance and even increase horsepower. I advise you to return to the articles (“The exhaust system of a motorcycle – what is its main task?”) And (“Self-cleaning of the exhaust system of a motorcycle”), from which we have highlighted the main tasks of the exhaust unit.

The motorcycle exhaust system must provide a clear exhaust and cooling of gases so that the reflected gas flow returns to the exhaust valve by the time it is next opened. The newer the motorcycle model, the more complex and thoughtful the gas evacuation will be.

Shape and length

First of all, let’s touch on this aspect of the issue. Let me remind you that the volume of the exhaust pipe must be several times greater than the volume of the cylinders. Therefore, short tailpipes are less efficient than long tailpipes. Gases from short systems will always be hotter and more hazardous to the pilot’s legs.

Secondly, the shape of the exhaust pipe must be as smooth and rounded as possible. Sharp corners will slow down the movement of gases and heat up the bend, which means that a burnout or crack will occur in the bend, and this is repair, hassle and disgruntled users.

I would like to refer to the shape of the configuration of the exhaust system, namely, two pipes coming out of each cylinder, or maybe 2 in 1 system, and maybe all 4 in 1. There is even an interesting transitional option 4 in 2 and these 2 in 1 exhaust pipe …

The configuration of the exhaust system will very much depend on the design of the engine. For two-stroke motorcycles, separate pipes are recommended for each cylinder, because in this case, the working volume of the exhaust system is so much larger than the engine displacement that the gases can expand enough upon exhaust to cool completely.

There are also more complex forms of spider collectors, which are connected to a common diffuser.

An exhaust manifold

People call it “knee” for its characteristic bend. We have already talked about soft rounded shapes. It’s time to deal with 4-in-1 and 4-in-2 systems. There is nothing to be smart about, everything is elementary. When the engine has 4 outlets in the manifold, 1 per cylinder, which are then quickly connected to 1 and go to the muffler.

The 4-in-1 system is recognized as one of the most successful at high rpms, which is why it is so popular among professional motorcycle races and sports models.

Collectors with a long connection in 1 make the transition from 4 to 2 in 1, but this is not a very popular type, although they are good for amateurs and beginners, as they improve performance on a wider range of rpm than 4 in 1, which works out for everything 100,000 at increased loads.

As for the material, the collectors absorb the first blow of the hot gases. Therefore, they are made mainly of stainless steel.

After stopping the engine, condensation forms inside the exhaust system in the manifold. If you have a cast iron manifold, condensation can cause corrosion.

There are also ceramic collectors. An interesting topic for those who are vitally important to reduce the weight of the motorcycle. Ceramic manifolds weigh really little, but they wear out at the same rate of exhaust gases, quickly crack and require replacement. On the other hand, if you are a professional race track pilot, and after the race you change almost half of the consumables, starting with tires and ending with the chain, why not change the manifold too, since such a booze has started?

For civilian motorcyclists, stainless steel is still a safe bet, because it is not afraid of condensation and is quite durable.


The intermediate part of the exhaust system between the knee and the muffler. It usually expands the gases to cool before leaving the pipe.


The most beloved, tasty and tasty part of the exhaust system. It is she who, with all her bells and whistles, is responsible for the timbre of the voice of your motorcycle. It is the “can” that pilots endlessly change when they do not like the sound of the exhaust.

By the way, inside the muffler you can find different fillings from catalysts and filters to Db Killer, he also responds to the “flute” among mere mortals, and we almost forgot about the power valve! Now one by one.

  • Catalysts and filters are fillings that are designed to bring the motorcycle exhaust to the required environmental standard. They are not everywhere, but they are quite common in young models.

  • Db Killer / flute – a system inside the case with many channels and holes through which gases pass. The system is designed to increase resistance to gas flows. If you take out the flute, the system turns into a direct-flow analogue with a completely different exhaust sound and less gas resistance.

There are models of exhaust systems in which you can adjust the opening of the flaps by pressing a button on the steering wheel, thereby boosting the exhaust and sound depending on the situation. An example of such a system would be Dr. Jekill & Mr. Hyde, which comes with a steering wheel control button and can already be installed on many top brands.

  • The power valve is its essence in the distribution of the reflected wave of the gas flow. This is done so that the gas flow does not reach the outlet valve when it closes. The valve allows only those reflected waves to pass through, which contribute to filling the cylinder and getting rid of the waste excess. The most famous SAEC systems are Suzuki, EXUP is Yamaha.

According to the materials of manufacture, popular steel:

  • Carbon
  • Stainless steel
  • Titanium
  • Aluminum

So, we found out that the exhaust system of a motorcycle is quite complex and multifaceted. The newer the motorcycle model, the more sophisticated its exhaust system will be. In the electronic age, many motorcycle functions rely on electrical feedback. So, for example, when removing the chip, the motorcycle may not start, but only treacherously blink a light on the panel, indicating that the focus has failed. The remote control of the exhaust level is also an interesting innovation, along with the constant development of the engineers.

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