ISO 23274-1:2019

Overview

ISO 23274-1:2019 - "Hybrid-electric road vehicles - Exhaust emissions and fuel consumption measurements - Part 1: Non-externally chargeable vehicles" specifies a chassis dynamometer test procedure to measure exhaust emissions, electric energy use and fuel consumption of non‑externally chargeable hybrid-electric vehicles (HEVs). The standard applies to passenger cars and light-duty trucks whose rechargeable energy storage system (RESS) has at least 2% of the total ADT energy consumption, and to vehicles with internal combustion engines (ICE) running on liquid fuels (e.g., gasoline, diesel). It also provides correction procedures when the RESS state of charge (SOC) changes during an applicable driving test (ADT).

Key topics and technical requirements

• Scope and applicability: Passenger cars and light-duty trucks, non‑externally chargeable HEVs (RESS ≥ 2% of ADT energy); ICE using liquid fuels. Can be applied to externally chargeable HEVs operated in charge-sustaining mode.
• Test method: Chassis dynamometer testing following the relevant regional ADT (applicable driving test) such as WLTC or UDDS (examples).
• RESS and SOC handling: Procedures for preconditioning, SOC adjustment, measurement of RESS energy balance (ΔERESS) and charge balance; methods for correcting emissions/fuel results when SOC does not remain constant.
• Instrumentation & accuracy: Required measurement accuracies include time (±0.1 s), distance (±0.1%), temperature (±1 °C), speed (±1%), mass (±0.5 kg), current and voltage (±0.5% full scale or ±1% of reading).
• Environmental and vehicle conditions: Ambient temperature (25 ± 5 °C); vehicle conditioning, test mass, tyres, lubricants, gear selection, and regenerative braking enabled for testing (with specific provisions for dynamometer coast-down).
• Dynamometer requirements: Calibration, warm-up, single-axle vs. double-axle arrangements, and road-load reproduction per ISO 10521 series.
• Correction methods & annexes: Includes linear correction coefficient, allowable RESS energy change, linear regression theory, and detailed charge-balance measurement guidance (Annexes A–D).

Practical applications and users

• Vehicle manufacturers and powertrain engineers: For R&D, validation and compliance testing of HEV emissions and fuel economy.
• Test laboratories and certification bodies: To perform standardized chassis dynamometer testing and report corrected emissions/fuel consumption when RESS SOC varies.
• Regulators and policymakers: To harmonize test methods and interpret HEV emissions/fuel data for regulatory compliance and labeling.
• OEM quality and homologation teams: For vehicle type approval, documentation and comparison with ISO 23274‑2 (externally chargeable HEVs).

Related standards

• ISO 23274 series (Part 2 covers externally chargeable HEVs - charge-sustaining operation)
• ISO 10521 - Road load determination for chassis dynamometer testing
• ISO/TR 8713 - Electrically propelled road vehicles - Vocabulary

Keywords: ISO 23274-1:2019, hybrid-electric road vehicles, exhaust emissions, fuel consumption measurements, chassis dynamometer, RESS, SOC, HEV testing, ADT, WLTC, regenerative braking.