China VI emission standard testing verifies that light-duty and heavy-duty vehicles meet the strictest emission limits ever enforced in China under GB 18352.6-2016 and GB 17691-2018. Accredited third-party laboratories perform laboratory and real-driving tests covering tailpipe pollutants, evaporative emissions, OBD systems, and durability. This article explains the technical scope, testing items, methods, and application scenarios of China VI compliance testing.
Technical Overview
China VI (National Stage VI) is the sixth and most stringent phase of China's motor vehicle emission control program, modeled on Euro 6 but with several limits and procedures that exceed the European baseline. The framework consists of two core standards: GB 18352.6-2016 for light-duty vehicles, which replaced China 5 and introduced the sub-stages China 6a (mandatory from July 1, 2020) and China 6b (mandatory from July 1, 2023), and GB 17691-2018 for heavy-duty compression-ignition and gas-fuelled positive-ignition engines, phased in between 2019 and 2023 depending on vehicle category.
Compared with China 5, the China 6b limits for key pollutants from light-duty vehicles are roughly 40–50% tighter, evaporative emission limits are cut by around 65%, and real driving emissions (RDE) testing became a mandatory type-approval requirement from the outset. The regulation also introduces particle number (PN) limits, nitrous oxide (N2O) limits, extended low-temperature testing, strengthened OBD requirements, and, for heavy-duty vehicles, remote emission monitoring. Compliance testing must be carried out by accredited third-party laboratories or competent technical authorities using equipment and procedures traceable to the referenced standards.
Testing Samples
Light-Duty Vehicles
Complete vehicles of categories M1, M2, and N1 with a gross vehicle mass not exceeding 3,500 kg, covering gasoline, diesel, natural gas, and hybrid powertrains. Plug-in hybrid and range-extended vehicles are tested in both charge-depleting and charge-sustaining modes, with results weighted by the utility factor. Complete vehicle test samples must be representative of the production configuration, including engine calibration, aftertreatment system, tires, and aerodynamic state.
Heavy-Duty Vehicles and Engines
Diesel and gas engines intended for categories M2, M3, N2, and N3, tested either as bare engines on engine dynamometers or as complete vehicles with portable emission measurement systems (PEMS). Samples include urban buses, freight trucks, and special-purpose vehicles equipped with EGR, DOC, DPF, SCR, and ammonia slip catalyst configurations.
Components and Subsystems
When required by the certification authority or for engineering development, testing also covers aftertreatment components (three-way catalysts, diesel oxidation catalysts, particulate filters, SCR systems), evaporative control components (carbon canisters, fuel tanks, filler necks, vapor hoses), OBD sensors, and remote emission monitoring terminals.
Testing Items
China VI light-duty testing under GB 18352.6-2016 comprises a family of type tests, each addressing a specific emission pathway:
- Type I test: gaseous and particulate emissions over the WLTC cycle, including CO, THC, NMHC, NOx, N2O, PM mass, and PN number.
- Type III test: crankcase emission verification.
- Type IV test: evaporative emissions from the fuel system, combining a hot soak phase and a 48-hour diurnal temperature profile.
- Type V test: durability of pollution control devices over 160,000 km, used to establish deterioration factors.
- Type VI test: low-temperature cold-start emissions (CO and NMHC) at −7°C.
- RDE test: on-road NOx and PN evaluation using portable analyzers under real traffic conditions.
- OBD system verification: functional checks, fault detection thresholds, and in-use performance ratio monitoring.
Heavy-duty testing under GB 17691-2018 covers WHTC and WHSC engine dynamometer cycles (including CO, NMHC, CH4 for gas engines, NOx, NH3 slip, and PM/PN), plus PEMS-based production conformity, in-service conformity, and market surveillance testing, together with OBD and remote emission monitoring validation.
Typical China 6b limits for Class 1 light-duty gasoline vehicles illustrate the stringency of the standard:
- CO: 500 mg/km
- THC: 50 mg/km
- NMHC: 35 mg/km
- NOx: 35 mg/km
- N2O: 20 mg/km
- PM: 3.0 mg/km
- PN: 6 × 10¹¹ particles/km
Testing Methods
Chassis Dynamometer Testing (Type I, VI)
Vehicles are conditioned in a temperature-controlled soak area (typically 6–36 hours at 23°C, or −7°C for the low-temperature test) and then operated over the Worldwide Harmonised Light Vehicles Test Cycle (WLTC) on a four-wheel-drive chassis dynamometer with representative road load and inertia settings. Exhaust is diluted using a full-flow constant volume sampling (CVS) system; CO and CO2 are measured by NDIR, total hydrocarbons by flame ionization detection, methane by gas chromatography, NOx by chemiluminescence, PM mass by gravimetric filtration, and PN by a condensation particle counter with a volatile particle remover.
Evaporative Emission Testing (Type IV)
The vehicle is placed in a variable-temperature sealed enclosure for evaporative determination (VT-SHED). Emissions are quantified during the hot soak phase immediately after dyno conditioning and during a 48-hour diurnal temperature profile, with total hydrocarbon accumulation compared against the applicable limit.
Real Driving Emissions Testing
PEMS equipment is mounted on the vehicle to record exhaust flow, pollutant concentrations, GPS position, and ambient conditions during a public-road route of 90–120 minutes with roughly balanced urban, rural, and motorway segments. Results are processed with the moving averaging window method and evaluated using conformity factors for NOx and PN.
Heavy-Duty Engine and Vehicle Testing
Engines are tested on dynamometers over the transient WHTC and steady-state WHSC cycles with full-flow dilution or partial-flow PM sampling, including NH3 measurement downstream of SCR systems. In-service conformity is verified with PEMS on actual in-use vehicles using CO2-based or work-based window evaluation.
Durability Evaluation (Type V)
Deterioration factors are established by aging a complete vehicle over 160,000 km on test tracks, public roads, or dynamometers, or by applying approved bench-aging and calculation procedures for aftertreatment systems.
Applications
China VI test reports and certificates support a wide range of regulatory and commercial purposes:
- Type approval and market access announcements for new vehicle models and engine families.
- Conformity of production (COP) verification to demonstrate that mass-produced vehicles continue to match certified configurations.
- In-service conformity and regulatory market surveillance testing organized by environmental authorities.
- Import vehicle inspection and customs clearance for models introduced from overseas markets.
- Manufacturer research and development, including calibration optimization, aftertreatment sizing, and pre-compliance screening before official submission.
FAQ
What is the difference between China 6a and China 6b?
China 6a was an interim stage with limits approximately 30–50% stricter than China 5, while China 6b imposes the full final limits, including stricter CO, NOx, and PM values and mandatory RDE conformity evaluation. New light-duty vehicles sold nationwide after July 1, 2023 must comply with China 6b.
How does China VI compare with Euro 6?
China VI adopts the WLTC cycle and many Euro 6 technical elements, but tightens several limits, imposes RDE from the beginning rather than in later phases, adds N2O limits, applies PN limits to all direct-injection gasoline vehicles, and requires stricter evaporative control and remote monitoring for heavy-duty vehicles.
Do electric and hybrid vehicles require China VI testing?
Pure battery-electric vehicles are exempt from exhaust emission tests but must meet separate electrical safety and general vehicle standards. Conventional hybrids and plug-in hybrids are fully within the scope of GB 18352.6-2016, with additional weighting procedures for charge-depleting operation.
What documents are needed to start a test project?
Typical submissions include the vehicle or engine technical specification, emission control system description, OBD documentation, fuel and lubricant information, durability plan, and prior certification records. Accredited third-party laboratories confirm sample configuration against these documents before testing begins.
How long does a complete China VI assessment take?
Individual laboratory tests such as a Type I cycle can be completed within days, but a full type-approval program including durability accumulation, RDE campaigns across temperature and altitude conditions, and OBD verification usually extends over several months. Early planning and pre-compliance screening help minimize project timelines.
