How to Analyze Exhaust Emission Test Results

Analyze Exhaust Emission

Normally when in the workshop, all Tune-Up, while ending with the term Set / Check CO.

Not just about the problem of environmental pollution, but from the emissions test we can find out if there is damage to the car and of course we could make fuel efficient.

In support of environmental preservation efforts, the countries in the world are starting to realize that the vehicle exhaust is one pollutant or source of air pollution largest therefore, vehicle exhaust gases must be made as much as possible so as not to pollute the air.

In countries that have vehicle emission standards are tight, there are five elements in vehicle exhaust gases to be measured are compounds HC, CO, CO2, NOx compounds O2dan. While in countries that are not too stringent emission standards, measuring only 4 elements in exhaust gases are compounds HC, CO, CO2 and O2.

Hydrocarbon Compounds Emissions

Gasoline is a hydrocarbon compound, so every HC obtained in vehicle exhaust indicates unburned gasoline and wasted along with the rest of the combustion. If a perfect burnt hydrocarbons (reacting with oxygen) then the result of the combustion reaction is carbon dioxide (CO2) and water (H¬2O). Although the ratio between air and fuel (AFR = Air-to-Fuel-Ratio) is appropriate and supported by the design of the combustion chamber when the engine is already close to the ideal, but still, most of the gas as if still can â € œbersembunyiâ €? ? of fire during a combustion process and cause the HC emissions at the tailpipe is quite high.

For a car that is not equipped with a catalytic converter (CC), HC emissions that can be tolerated is 500 ppm and for cars equipped with CC, HC emissions that can be tolerated is 50 ppm.

The HC emissions can be reduced by providing additional heat and oxygen outside the combustion chamber to complete the combustion process. Oxygen injection process right after the exhaust port will be able to suppress the HC emissions drastically. Currently, some car engines are equipped with electronic water pump direct-injection reaction works when cold-start to reduce HC emissions CC shortly before reaching the ideal working temperature.

If the high HC emissions, shows there are 3 possible causes that CC does not work, AFR improper (too rich) or gasoline does not burn completely in the combustion chamber. If the car is equipped with CC, it must be tested prior to the CC denganc fig measure the temperature difference between inlet and outlet CC. Supposedly the temperature at the outlet will be at least 10% higher than inletnya.

If CC works normally but HC stays high, then it is a symptom that AFR improper or misfire occurs. AFR is too rich will cause the emission of HC is high. This bias is caused partly leak fuel pressure regulator, carburetor settings are not appropriate, a clogged air filter, engine temperature sensor is not normal and so on that can make the AFR is too rich. Dirty injectors or fuel pressure that is too low can make gasoline granules become too big to burn dengna perfect and it also will make HC emissions is high. Whatever the reason, which is too rich AFR also be made into a high CO emissions and even lead to the outlet of the CC overheated, but high CO and HC can also be caused by rembasnya lubricant into the combustion chamber.

If only high HC, it should explore the causes that make the ECU ordered petrol injectors to spray just a little so that the AFR is too thin that causes intermittent misfire. In cars still use carburetors, among other causes misfire is not a good spark plug wires, ignition timing is too backward, air leaks around the intake manifold or mechanical problems that cause low engine compression numbers.

For cars equipped with EFI system and CC, this misfire symptoms should be addressed immediately because if allowed to stand, the ECU will continuously strive to make AFR become rich as read that there is still unburned oxygen. Consequently CC will overheat.

Emissions of Carbon Monoxide (CO)

Carbon monoxide gas is a gas that is relatively unstable and tend to react with other elements. Carbon monoxide, can be changed easily to CO2 with the help of a little oxygen and heat. When the machine is working with the appropriate AFR, emissions of CO in the exhaust end of the range of 0.5% to 1% for machines equipped with injection systems or approximately 2.5% for machines that still use carburetors. With the help of water injection system or CC, the CO can be made as low as possible close to 0%.

If the AFR little richer than the ideal figure (ideal AFR = lambda = 1.00), the CO emissions will rise dramatically. So high rates of CO indicate that AFR is too rich, and this could be due to, among others, due to problems in the fuel injection system such as the fuel pressure is too high, the engine temperature sensor is abnormal, a dirty air filter, PCV system is not normal, dirty carburetor or improper settings.

Emissions of Carbon Dioxide (CO2)

CO2 concentrations indicate directly the status of the combustion process in the engine. The higher the better. When AFR is in an ideal figure, CO2 emissions ranged from 12% to 15%. If the AFR is too lean or too rich, then the CO2 emissions will drop drastically. If CO2 is below 12%, then we have to look at other emissions that indicates whether the AFR is too rich or too thin.

Keep in mind that this is only a source of CO2 combustion chamber and CC. If CO2 is too low but the CO and HC normal, indicating leakage of exhaust pipe.

Oxygen (O2)

The concentration of oxygen in the exhaust gases of vehicles is inversely proportional to the concentration of CO2. To get a more complete combustion process, the amount of oxygen into the combustion chamber should be sufficient for any hydrocarbon molecules.

In the combustion chamber, a mixture of air and gasoline can burn perfectly if the shape of the combustion chamber curved perfectly. This condition allows the molecules of gasoline and air molecules can be easily met to react perfectly to the combustion process. But unfortunately, the combustion chamber can not be perfectly curved and smooth so as to allow the gas molecules as if hiding from molecular oxygen and cause the combustion process to be completed.

To reduce HC emissions, then it takes a little extra air or oxygen to ensure that all gas molecules can â € œbertemuâ € ?? with molecular oxygen to react perfectly. This means AFR of 14.7: 1 (lambda = 1.00) is actually a condition that is a little thin. This is what causes the oxygen in the flue gas will range between 0.5% to 1%. On machines equipped with CC, this condition will be good because it helps the CC function to convert CO and HC into CO2.

The machine can still work well although AFR AFR too thin even to reach 16: 1. But in these conditions will arise other effects such as machines tend knocking, engine temperature increases and emissions of NOx compounds will also increase dramatically.

Normally the concentration of oxygen in the exhaust gas is approximately 1.2% or less even possible 0%. But we must be careful when oxygen concentration reaches 0%. This shows that can be used up all the oxygen in the combustion process and this can mean that tend to be rich AFR. In such conditions, the low oxygen concentration will coincide with high CO emissions. If the high oxygen concentration can mean AFR too thin but also can indicate some other things. When coupled with high CO and HC, then the car is equipped with CC CC means damaged. For a car that is not equipped with the CC, when oxygen is too high and the other low means there is a leak in the exhaust sytem.

Emissions of NOx compounds

In addition to the above four gas, NOx emissions are not overlooked in making the diagnosis of the machine. NOx compounds are chemical bonds between nitrogen and oxygen. Under normal conditions the atmosphere, nitrogen is an inert gas that is very stable which will not bind with other elements. But under conditions of high temperature and high pressure in the combustion chamber, the nitrogen will break ties and binds with oxygen.

NOx compounds is very unstable and when released into the air, will bind with oxygen to form NO2. This is very dangerous because these compounds are highly toxic, and when exposed to water to form nitric acid.

The high concentration of NOx compounds due to the high oxygen concentration coupled with the high temperature of the combustion chamber. To keep the NOx concentration is not high, it is necessary to precisely control the temperature of the AFR and combustion chamber must be maintained so as not too high either with EGR and long valve overlap. Normally NOx at idle does not exceed 100 ppm. If the AFR is too thin, the ignition timing is too high or other causes which led to the combustion chamber temperature increases, will increase the concentration of NOx and this will not be overcome by the CC or advanced 

EGR system though.

Piles of carbon crust is in the combustion chamber will also increase the compression engine and can cause hot spots that can increase levels of NOx. Machines are often detonation will also lead to high concentrations of NOx.

To help us analyze the condition of the engine, we can use as an aid in the description below:

1. high CO emissions, showing a condition where too rich AFR (lambda <1.00). In general, CO showed the efficiency of combustion in the combustion chamber. The high CO emissions caused by lack of oxygen to produce a complete and perfect combustion.

Things that cause too rich AFR, among others:

- Idle speed is too low.

- Settings improper carburetor float causing too much gasoline.

- Air filter is dirty.

- Lubricants machine is too dirty or heavily contaminated.

- Charcoal Canister saturated.

- PCV valve that is not working.

- The performance of the fuel delivery system is not normal.

- Air intake temperature sensor is abnormal.

- Coolant temperature sensor is abnormal.

- Catalytic Converter that does not work.

2. Normal CO. If the AFR is close to or right at the ideal point (AFR 14.7 or lambda = 1.00), the CO emissions will not be more than 1% on the engines with injection systems or 2.5% on the engines with carburetors.

3. CO is too low. Actually there is no limit where CO is said to be too low. The concentration of CO sometimes still visible â € œnormalâ € ?? even though the machine has been working with a very thin mixture.

HC 4.Emisi high. Generally, this condition indicates the presence of excess unburned gasoline due to the failure of the ignition system or incomplete combustion. HC concentration measured in ppm (parts per million). Common causes are not qualified ignition system, a leak in the intake manifold, and problems in the AFR.

Other causes are:

- Incomplete combustion due to the spark plug is damaged.

- Ignition timing is too backward.

- The cable plugs are damaged.

- Low compression engine.

- Leaks in the intake.

- Error reading data by ECU causing too rich AFR.

5. Concentration of Oxygen. Indicates the amount of air entering the combustion chamber is proportional to the amount of gasoline. The ideal number for oxygen in exhaust emissions ranged from 1% to 2%.

6. The high oxygen concentration. It shows that the AFR is too thin.

Conditions that lead to, among others:

- AFR improper.

- Leaks in the intake tract

- The failure of the ignition system that causes misfire

7. The low oxygen concentration. This condition indicates that the AFR is too rich.

8. elevated CO2 concentration. This condition indicates that the AFR is close to or right in ideal conditions.

9. The low CO2 concentrations. This condition indicates that the AFR is too lean or too rich and leaks in the exhaust system.

10. The concentration of NOx compounds. NOx compounds including nitric oxide (NO) or nitric oxide (NO2) is formed when the temperature of the combustion chamber reaches more than 2500 degrees F (1350 ° C). These compounds can also be formed when the machine gets heavy loads.

11. The high concentration of NOx.

This indicates:

- EGR Valve does not work.

- AFR too thin.

- Spark Advancer that does not work.

- Thermostatic Water Heater jammed.

- Damage to the cold air duct.

- High crust deposits in the combustion chamber.

- Catalytic Converter abnormal.

12. The low NOx concentration. Actually there is no restriction that states too low emissions of NOx compounds. Generally NOx is 0 ppm when the machine is idle.

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