The Ministry of Agriculture and Environment explains why vehicle emissions testing requires 'flooring the gas pedal'.
The Ministry of Agriculture and Environment stated that when the engine accelerates rapidly, the operating state becomes more stable, maximum smoke is produced and passes through the exhaust pipe to the measuring device. Therefore, the test results can more accurately reflect the actual emission levels of the vehicle.
According to the Ministry of Agriculture and Environment (MARD), the method of measuring car emissions at high RPM – often understood as "flooring the accelerator" – in the National Technical Standard QCVN 85:2025/BNNMT is not actually a new regulation, but has been applied before and is based on international standards.
Representatives from the Ministry of Agriculture and Environment stated that the scientific basis of the current emission measurement method is built upon international standards that have been adapted into Vietnamese standards. Emission testing for each type of engine has specific procedures and technical standards.
Specifically, for automobiles using forced-ignition engines (gasoline), the concentrations of CO and HC in exhaust gases are determined according to TCVN 6204:2008 on methods for measuring exhaust emissions during inspection or maintenance of road vehicles. This standard, published by the Ministry of Science and Technology, is based on a conversion from ISO 3929:2003 of the International Organization for Standardization (ISO).
For automobiles using compression ignition engines (diesel fuel), the measurement of exhaust smoke opacity is carried out according to TCVN 7663:2007. This standard specifies the measurement method based on the engine's free acceleration cycle, and is derived from ISO 11614:1999.
According to the Ministry of Agriculture and Environment, ISO is an international standardization organization with the participation of national standards bodies from more than 160 countries. Therefore, the measurement method in free acceleration mode, at high RPM, is a technical practice that has been widely applied worldwide.
The Ministry also stated that the regulations in QCVN 85:2025/BNNMT still use the same measurement methods as before, unchanged from the period prior to the implementation of the vehicle emission control roadmap.
Further explaining the reason for measuring emissions at high RPMs, the Ministry of Agriculture and Environment stated that when the engine operates at high idle speeds, the combustion process in the combustion chamber closely resembles the actual conditions when the vehicle is in motion on the road.
When the engine accelerates rapidly, the operating state becomes more stable, maximum smoke volume is produced and travels through the exhaust pipe to the measuring device. This allows the test results to more accurately reflect the vehicle's actual emissions.
Conversely, if measurements are taken at low idle speeds, the combustion chamber temperature and exhaust gas treatment devices often haven't reached a stable operating state, which may result in inaccurate readings that don't reflect actual vehicle emissions during operation.
Used cars may incur maintenance costs.
From a technical perspective, Mr. Le Chi Thien, the owner of an auto repair shop in Hanoi, believes that, in principle, engines are designed by manufacturers to withstand high RPMs within permissible limits. However, the level of safety also depends on the actual condition of the vehicle.
According to Mr. Thien, for new vehicles with well-functioning engines, revving the engine to full throttle to check emissions usually doesn't cause significant problems. However, for vehicles that have been used for many years, especially trucks that frequently operate at high intensity or carry overloaded loads, a sudden increase in engine speed can pose potential risks.
After prolonged use, many engine components such as connecting rod bearings, piston rings, or connecting rods can wear down, creating clearances. When the engine is subjected to sudden and heavy forces due to full throttle acceleration, these components can be affected, and in the worst case, this can lead to connecting rod seizure or breakage.
Therefore, for older or heavily used vehicles, owners often have to service or overhaul the engine before passing the vehicle inspection to ensure safety. The repair costs vary depending on the vehicle's condition and can amount to tens of millions of VND or more, causing some owners to incur additional expenses before the emissions test.
Furthermore, some vehicle inspection centers now require vehicle owners to sign a commitment in case the engine is at risk of damage when performing acceleration maneuvers for emissions testing. According to Mr. Thien, this approach is not really reasonable.
He argued that during inspections, inspectors should observe and evaluate based on their technical intuition as well as parameters from measuring equipment. If they notice any abnormalities in the engine or if the emissions results indicate a potential failure to meet standards, the inspection should be temporarily halted and the vehicle owner advised to have the vehicle repaired.
According to Mr. Thien, the appropriate solution is to detect and warn early so that vehicle owners can address the issue before re-inspection, instead of waiting for the risk to occur and then requiring the vehicle owner to take responsibility for any potential damage.
