Recently, the application of a new emission testing method for cars using diesel engines (compressed combustion engines, diesel engines) is attracting the attention of many vehicle owners.
Some car owners and drivers expressed concern that checking emissions by pedaling the throttle to the end of the journey ("floor kick") in unloaded condition may increase the risk of engine or technical details being damaged. In fact, some cases of cars encountering problems after inspection have been recorded, leading to many debates about this measurement method.
However, registration facilities said that emission inspection must be carried out according to the procedures and instructions of the Vietnam Register. In some cases, if the maximum unloaded speed limit of the engine cannot be determined according to the manufacturer's regulations, vehicle owners must sign a commitment to accept technical risks (if any), then the registration facility will conduct emission inspection.
According to the guidance of the Vietnam Register, the emission control process for diesel engine vehicles includes 3 main steps: preparing and checking vehicle safety; performing emission measurement; recording measurement results.
Prepare the means before measuring
Before the exhaust gas test, the vehicle must ensure basic technical conditions. Engine lubricant and coolant must be sufficient as recommended by the manufacturer. The engine must be fully heated, the minimum lubricant temperature must reach 60°C or determined by the engine cooling fan running.
The exhaust system must be tightly sealed, without leaks; loading equipment such as air conditioners, lights and other electrical equipment must be turned off.
After that, the vehicle inspector conducts a safety inspection and cleans the exhaust system. The engine is allowed to run in idle mode for at least 1 minute to stabilize and detect abnormalities. Next, perform at least two accelerations to check the engine's operation and clean the exhaust system.
During acceleration, the accelerator pedal is pedaled slowly at unloaded speed until the end of the journey for a minimum of 5 seconds to check the accelerator and determine the maximum unloaded speed of the engine. Then continue to accelerate for about 2–5 seconds to clean up the exhaust system.
The Vietnam Register notes that the maximum unloaded speed when inspecting must not exceed the limit according to the manufacturer's regulations. If this limit cannot be determined, the inspection can only be continued when the vehicle owner signs a written commitment to be responsible for technical risks that may arise.
A free acceleration test will not be performed if abnormal signs are detected such as the engine making a metal tapping sound, strong vibration when accelerating, the accelerator operating incorrectly, fuel or lubricant leakage, or the engine fault light not turning off when the engine is in operation are detected.
Implement emission measurement
The emission measurement process is performed when the engine operates stably at the lowest idling speed. The gear lever must be in the intermediate position (number N for manual transmission; number N or P for automatic transmission). The idling speed of a conventional engine does not exceed 1,000 rpm, unless otherwise specified by the manufacturer.
After installing the exhaust sampler head and engine speed sensors, the inspector proceeds to accelerate quickly and continuously to achieve the maximum speed of the engine before unleashing the accelerator.
For passenger cars with 9 seats or more or trucks with a total weight of 3.5 tons or more, the time from starting to pedal the accelerator to unloading the gas must be no less than 2 seconds. After reaching the regulated fuel stopping speed, the accelerator pedal must be completely unloaded so that the engine automatically reduces speed to unloaded mode.
The measurement cycle is repeated until there are 3 consecutive valid measurements, in which the difference between the largest and smallest measurement values does not exceed 10% HSU.
Recording results and commitment responsibilities
The results of each measurement include parameters such as smoke density (% HSU), idling engine speed, maximum engine speed, acceleration time, and maintenance time. The final emission result is determined by the average value of 3 consecutive valid measurements.
The Vietnam Register also requires registration facilities to clearly notify vehicle owners of the measurement process using the free acceleration method and technical risks that may occur if the vehicle is not properly maintained or the acceleration system operates unstablely.
In case the vehicle owner agrees to continue the inspection, the registration inspector will guide the preparation of a commitment form. This document is made in two copies, one copy stored in the inspection file and one copy handed over to the vehicle owner.
If the vehicle owner does not agree to sign a commitment, the registration facility will stop the emission inspection item and notify the vehicle that it does not meet inspection standards because it does not meet safety conditions to perform the measurement.
