market dynamics
Motorcycle secondary intake is the exhaust gas into the cylinder to burn? In the wrong!
Release date:2020.04.26

The motorcycle's secondary intake working principle, many people think is the exhaust gas into the engine cylinder combustion, the actual work is not like this, is in the exhaust gas at the same time into the exhaust pipe into the fresh air. Some people may not understand, so how can play a role in reducing carbon monoxide in the exhaust gas?

According to abroad have done many experiments, found at the end of the engine at the beginning of the exhaust gas and the exhaust, the discharge of harmful gases such as carbon monoxide concentration, the exhaust temperature to a certain extent, if at this time in oxygen, will be able to speed up the harmful gases such as carbon monoxide oxidation process, so as to reduce the exhaust the harmful gas such as carbon monoxide.

Secondary air supply system is the direct input of fresh air into the high temperature exhaust gas, to promote the oxidation of HC and CO in the exhaust gas system to H2O and CO2.

The principle of secondary air intake is designed on this principle. You can see that the secondary air intake has three rubber pipes, one connected to the exhaust pipe branch, one connected to the air filter, and one connected to the carburetor negative pressure pipe.

If waste gas from the exhaust pipe branch into the air filter, and then into the engine cylinder, then into the air filter of waste gas account for 10% of the total waste gas has been good, moreover the air filter is not to save gas, into the exhaust gas from the air filter inlet, air filter can filter out harmful gases such as carbon monoxide in the exhaust gas, let this part of the gas burning again.


Even if it works like this, 5% of the waste gas that goes into the secondary combustion is a big deal, and that's not going to reduce the harmful gases in the exhaust.

The correct working principle is opposite, it is the air from the air filter into the exhaust pipe branch, and then into the exhaust pipe, and the waste gas mix, the waste gas such as carbon monoxide oxidation, thereby reducing the harmful gas in the waste gas, to achieve the purpose of environmental protection.

There's a simple way to show that this works: you can take the secondary intake and connect it to the air filter, pull it out, start the engine, put your hand on the interface, and you'll see that the gas is sucking in, not blowing out.

For the sake of environmental protection, please reserve the second intake. At present, domestic thermal reactors are mostly used together with secondary air injection devices to provide high temperature and oxygen-rich conditions for the reoxidation or combustion of HC and CO in the exhaust gas, so as to improve emissions. The device, which has been used in cars, is now obsolete.

Due to the requirement of simple structure and low cost, and the main pollutants discharged by the motorcycle are HC and CO, the device has certain application value in the motorcycle.

Structure principle: the secondary air supply device is composed of cylinder head, intake pipe, air supply pipe, air supply valve, air supply hose, air filter and negative pressure pipe. The air supply valve is composed of one-way valve and negative pressure control valve. In the original state, the one-way valve is in the normally closed state, and the negative pressure control valve is in the normally open state.

Assembly relationship: as shown in the following figure, there is a new air inlet on the exhaust channel of the cylinder head. The air inlet pipe is connected with the air inlet of the cylinder head. The air inlet valve is connected with the air inlet pipe.

In order to meet the requirements of national emission standards, the engine crankcase vents are connected to the oil and gas separator in series and then connected to the air filter, so as to avoid the pollution caused by the crankcase exhaust gas directly discharged into the atmosphere.

How it works: when the engine is running, the exhaust pressure in the exhaust duct of the cylinder head pulsates with the change of the working cycle of the engine. When the exhaust valve is opened, the high-temperature and high-pressure exhaust gas in the cylinder quickly enters the exhaust pipe, and the pressure starts to rise. In the exhaust pipe, a high-pressure pulse is generated, that is, a positive pressure wave is generated. At this time, the one-way valve in the air supply valve is in a closed state, which avoids the high-temperature exhaust reflux burning up the air supply valve and pipeline.

This pulse wave propagates along the exhaust pipe. When the positive pressure wave propagates in the exhaust pipe with the pipe section increasing gradually, the gas density decreases, and a negative pressure wave is generated to return. In the exhaust pipe near to fill the position of the trachea to form a negative pressure, then one side of the check valve is the atmospheric pressure, negative pressure on one side, fill gas check valve in the open under the action of pressure difference, take the fresh air through the air filter, air hose, air valve and tonic. Gas exhaust duct steel pipe to cylinder head, to exhaust the harmful gas CO, HC provides more sufficient oxygen oxidation.

When motorcycle speeding but suddenly reduce oil, close to the carburetor throttle closed, and motorcycle driving moment of inertia is larger, driven by the engine at high speed, the engine air intake inadequate, lack of oxygen, burning slowly, after the muffler of trend, if still fill gas in this case, will cause after burning, resulting in serious shooting in the muffler.

In order to avoid shooting, the negative pressure control valve in the air supply valve will block the air supply path. When the motorcycle runs at high speed and suddenly reduces oil, the negative pressure in the intake pipe is large, and it is passed to the control chamber of the negative pressure control valve through the negative pressure pipe. Under the action of pressure difference, the valve core moves towards the closing direction to close the air path and stop the air supply.

Working principle of secondary air intake: on the basis of ou1 device (crankcase waste gas recovery and utilization), ou2 device is installed. First of all, the gas from the cylinder head was discharged, not inhaled. I took it apart, started it and tried it.

In addition, the incoming air from the combination valve direction is independent of the entry, not from the air filter access. The combined gas discharge is connected to the intake pipe between the carburetor and the engine interface.

It is the principle of a point in the exhaust pipe after the combustion of the reducible gas through the combination valve mixed with the filtered air, and finally mixed with the carburetor atomized gas into the intake valve. Each manufacturer's installation of Europe 2 device is generally the same in principle, but there are always differences in structure. I hope it will be helpful for you to repair this device.