Emission control regulations
There are various regulations for most countries around the world today to prevent the air pollutants by emission gases. These are called emission regulations. The measurement method or the standard value varies by each country. The differences of the representative measurement modes are easily introduced below.
U.S.A (LA#4 mode)
This simulates the complex driving pattern of the suburbs in Los Angeles. This mode is close to the actual vehicle driving conditions.
EU (New EC mode)
This driving mode has been added to the simulate highway driving for which NOx has the strictest regulations.
JAPAN (10.15 mode)
It is simulated the vehicle driving in the city with traffic signals.
Measurement of the concentration and total weight
There are two methods to measure the emission gas.
Measure what percentages of CO/ HC/NOx are included in the emission gas for measuring concentration.
Measuring total weight
For measuring total weight, simulate actual driving as in the illustration and measure the amount of CO/HC/ NOx emitted during the test. In recent years, measuring the total weight has become the major method. The amount of harmful gases that a vehicle generates is more important than the percentages of harmful gases.
Emission Control System
A high level of technology is necessary to ensue that the total weight of these three substances (CO, HC and NOx) in the emissions meets the emission regulations. For actual vehicles, it is necessary not only to decrease these substances but also to meet standards as a whole for vehicle devices in terms of durability, reliability, safety and fuel consumption. Emission purification countermeasures are listed in the table on the left, but devices vary by country and the emission regulations vary by region.
Improvement of Engine
The engine has been improved significantly to prevent the engine output and fuel consumption rate from worsening over time, preventing harmful gas generation as much as possible. The following items are not used on all types of engines, however, the most appropriate item for each engine is used.
1. Construction of combustion chamber and improvement of air intake system
(1) Adoption of squish area
The squish area in the combustion chamber generates strong turbulence starting from the end of the compression stroke into the combustion stroke. This turbulence increases the combustion speed and burns the air-fuel mixture completely, and decreases the CO and HC.
(2) Generation of swirl
The curved intake port causes the air-fuel mixture that is drawn in during the intake stroke to form the appropriate swirl toward the outer edge of the combustion chamber. This swirl continues from the compression stroke to the combustion stroke, and gives the same effect as the squish.
2. Adoption of EFI, ESA and DIS
Burns the air-fuel mixture completely and decreases the exhaust gas due to the adoption of EFI (Electronic Fuel Injection), which always makes the proper airfuel mixture, and ESA (Electronic Spark Advance) and DIS (Direct Ignition System), which finely regulates the ignition timing depending on the driving condition.