New vehicle emission testing is a mandatory evaluation process that verifies whether a newly manufactured vehicle meets national and international exhaust emission limits before it can be certified and sold in the market. This testing covers tailpipe pollutants, evaporative emissions, on-board diagnostics, and durability requirements using standardized laboratory and real-world driving procedures. Understanding the test samples, items, and methods involved is essential for automakers, importers, and regulatory compliance teams.
Technical Overview
New vehicle emission testing refers to the systematic experimental evaluation of exhaust and evaporative emissions from newly produced motor vehicles prior to market entry. The purpose of this testing is to confirm that a vehicle type, as designed and manufactured, complies with the applicable emission limits defined by regulatory standards such as GB 18352.6-2016 (China 6 for light-duty vehicles), GB 17691-2018 (China VI for heavy-duty engines), and equivalent frameworks in other jurisdictions.
Modern emission experiments are conducted in accredited third-party laboratories and manufacturer facilities equipped with climate-controlled chassis dynamometers, constant-volume sampling (CVS) systems, exhaust gas analyzers, particulate measurement instruments, and sealed housing for evaporative determination (SHED) chambers. The testing simulates real driving conditions through standardized driving cycles, environmental temperature control, and road-load replication to produce repeatable and legally defensible results.
Since the discovery of large-scale discrepancies between laboratory results and real-world emissions, regulatory frameworks have evolved to include real-driving emissions (RDE) testing with portable emissions measurement systems (PEMS), stricter particulate number (PN) limits, and extended in-service conformity verification. Consequently, new vehicle emission testing now spans the full vehicle lifecycle, from type approval to production consistency surveillance.
Testing Samples
Complete Light-Duty Vehicles
Passenger cars, light commercial vehicles, and multi-purpose vehicles powered by gasoline, diesel, hybrid, or natural gas engines constitute the primary test samples. Vehicles must be representative of the production configuration, including the exact engine calibration, aftertreatment system, transmission, tires, and vehicle mass class as declared in the type approval documentation.
Heavy-Duty Engines and Vehicles
For heavy-duty applications, testing may be performed on engine dynamometers using complete engines as samples, following the standards set out in GB 17691. Whole-vehicle verification using PEMS is also required to demonstrate compliance under actual operating conditions for trucks and buses.
Exhaust Aftertreatment Systems and Components
Catalytic converters, diesel particulate filters, selective catalytic reduction (SCR) systems, and oxygen sensors may be submitted as standalone samples for component-level evaluation, aging characterization, and system integration validation in support of whole-vehicle certification.
Fuel, Lubricant, and Reference Materials
Testing requires certified reference fuels with precisely controlled properties, calibration gases traceable to national metrology standards, and zero-grade air for analyzer baseline verification. These materials ensure that measured emission values are accurate and comparable across laboratories.
Testing Items
New vehicle emission experiments typically cover the following categories of test items:
- Gaseous regulated pollutants: carbon monoxide (CO), total hydrocarbons (THC), non-methane hydrocarbons (NMHC), methane (CH4), and oxides of nitrogen (NOx)
- Particulate pollutants: particulate mass (PM) and particle number (PN) emissions
- Additional pollutants under newer standards: nitrous oxide (N2O), ammonia (NH3) slip from SCR systems, and formaldehyde for certain fuel types
- Evaporative emissions: hydrocarbon vapor losses from the fuel system, including hot soak, diurnal, and running losses measured in SHED chambers
- Crankcase emissions: verification that blow-by gases are not released directly into the atmosphere
- On-board diagnostics (OBD): functional verification of OBD monitoring capability, fault detection thresholds, and malfunction indicator behavior
- Durability and deterioration: evaluation of aftertreatment performance over a standardized mileage accumulation period to establish deterioration factors
- Low-temperature and cold-start performance: CO and HC emissions at ambient temperatures as low as -7 °C, and extended testing at -30 °C under certain regional requirements
- CO2 emissions and fuel consumption: measured simultaneously with pollutant testing for corporate average fuel economy compliance
Testing Methods
Chassis Dynamometer Type Approval Testing
The core laboratory method places the complete vehicle on a chassis dynamometer that reproduces inertial and road-load forces. The vehicle is driven through the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) as specified in GB 18352.6, or through region-specific cycles such as the FTP-75 procedure used in North American regulatory programs. Exhaust is diluted and collected using a CVS system, and pollutant concentrations are quantified with flame ionization, chemiluminescence, and nondispersive infrared analyzers, with results expressed in mass per distance traveled.
Real-Driving Emissions (RDE) Testing with PEMS
Portable emissions measurement systems are mounted on board the vehicle to measure NOx, PN, and CO while the vehicle is driven on public roads under defined conditions of route dynamics, altitude, and ambient temperature. RDE testing validates that laboratory compliance translates into real-world performance and applies moving averaging windows and statistical evaluation methods to confirm conformity with not-to-exceed limits.
Evaporative Emission Testing in SHED Chambers
The vehicle is placed inside a sealed enclosure of known volume where hydrocarbon concentration is measured before and after conditioned test sequences. Procedures include the hot soak loss test after a warmed-up driving cycle and multi-day diurnal breathing loss tests with programmed temperature ramps, quantifying total hydrocarbon mass released from the fuel system.
Low-Temperature and Environmental Chamber Testing
Cold-start CO and HC emissions are evaluated in a temperature-controlled soak room maintained at -7 °C or lower, verifying catalyst light-off performance and fuel calibration under severe ambient conditions.
OBD System Verification
OBD testing involves deliberately introducing simulated faults, such as a defective catalyst, misfire conditions, oxygen sensor failure, or diesel particulate filter damage, to confirm that the monitoring system detects the fault, illuminates the malfunction indicator lamp, and stores the corresponding diagnostic trouble codes within regulated limits.
Durability Testing and Deterioration Factor Determination
Test vehicles are aged over a prescribed mileage schedule on test tracks or dynamometers, with periodic emission measurements to establish deterioration factors. These factors are applied to type approval results to demonstrate that emission limits continue to be met throughout the defined useful life of the vehicle.
Applications
New vehicle emission testing supports a wide range of regulatory, commercial, and engineering purposes:
- Type approval and certification: demonstrating compliance with national emission standards before a new vehicle model can be legally registered and sold
- Conformity of production: verifying that mass-produced vehicles continue to match the certified prototype through random factory sampling and testing
- In-service conformity: checking that vehicles in actual consumer use remain within emission limits over their service life
- Import and market access: providing the emission compliance documentation required for vehicles entering regulated markets
- Research and development: calibrating engine management systems, optimizing aftertreatment strategies, and validating design changes during vehicle development programs
- Regulatory investigation and recall support: investigating field complaints, verifying manufacturer self-certification data, and substantiating emission-related recall campaigns
- Environmental policy development: generating emission factor data used by government agencies for air quality modeling and standard-setting
FAQ
What is the difference between type approval testing and conformity of production testing?
Type approval testing is performed on representative prototype vehicles to certify that a new vehicle type meets emission standards before market launch. Conformity of production testing is performed on randomly selected vehicles from the serial production line to confirm that mass-manufactured vehicles remain consistent with the approved configuration over time.
What driving cycle is used for new vehicle emission testing in China?
Under GB 18352.6-2016, light-duty vehicles are tested using the Worldwide Harmonized Light Vehicles Test Cycle (WLTC), which features more dynamic speed profiles and higher load conditions than the earlier NEDC cycle, providing a closer approximation of real-world driving behavior.
Why is real-driving emissions (RDE) testing required in addition to laboratory testing?
Laboratory dynamometer tests are highly repeatable but may not fully represent actual on-road conditions. RDE testing with PEMS verifies that emission control systems perform effectively across diverse driving styles, traffic conditions, altitudes, and ambient temperatures, closing the gap between certified and real-world emissions.
What are evaporative emissions and how are they measured?
Evaporative emissions are hydrocarbon vapors that escape from the fuel tank and fuel system due to temperature changes and vehicle operation. They are measured by sealing the vehicle inside a SHED enclosure and analyzing the increase in hydrocarbon concentration following standardized hot soak and diurnal test procedures.
How long does new vehicle emission testing take?
The duration depends on the scope of the program. A single type approval test sequence may take several days of vehicle preconditioning and testing, while a full certification program including durability mileage accumulation, OBD verification, and evaporative testing can extend from several weeks to several months.
Do electric vehicles require emission testing?
Battery electric vehicles produce no tailpipe emissions and are exempt from exhaust emission testing. However, hybrid electric vehicles must complete all applicable emission experiments, including testing of their electric-only and charge-sustaining operating modes as defined in the relevant standards.