To be certified, a vehicle must demonstrate that its exhaust and evaporative emission control systems are durable and comply with the emission standards for the vehicle’s useful life. This is done through durability and certification testing of the prototype certification vehicle. Compliance with on-board diagnostics, anti-tampering, fuel tank fill-pipe and openings, crankcase emissions, etc., must be demonstrated also.
Each new car or engine need to be put through a test cycle, the base of the test is explained by the NEDC (New European Driving Cycle) trial. For certification purposes, vehicles are grouped in engine families or test groups for exhaust emissions and evaporative families for evaporative emissions. Within each family, the vehicles share similar designs and are expected to have similar emission characteristics. An “Executive Order” is issued to certify an engine family in combination with one or more evaporative families. An Executive Order is valid for production during the specified model year. Vehicles produced for another model year require another Executive Order.
Specific certification information is included in an Executive Order: vehicle model year, engine and evaporative families, vehicle category, emission standard category, engine displacements, operating fuel, emission control systems, values of the exhaust and evaporative emission standards and certification emissions, and vehicle models.
- The cycle must be performed on a cold vehicle at 20–30 °C. The cycles may be performed on a flat road, in the absence of wind. However, to improve repeatability, the tests are generally performed on a roller test bench. This type of bench is equipped with an electrical machine to emulate resistance due to aerodynamic drag and vehicle mass.
- For each vehicle configuration, a look-up table is applied: each speed corresponds to a certain value of resistance (reverse torque applied to the drive wheels). This arrangement enables the use of a single physical vehicle to test all vehicle body styles by simply changing the look-up table. A fan is coupled to the roller bench to provide the vehicle air intakes with an airflow matching the current speed. Many more tests can be performed during vehicle development with this arrangement than with conventional road tests.
- The test is conducted with all ancillary loads turned off (Air conditioning compressor and fan, lights, heated rear window, etc.)
ECE R15 cycle, or better known as The Urban Driving Cycle
The cycle has been designed to represent typical driving conditions of busy European cities, and is characterized by low engine load, low exhaust gas temperature, and a maximum speed of 50 km/h.
- When the engine starts, the car pauses for 11 s – if equipped with a manual gearbox, 6 s in neutral (with clutch engaged) and 5 s in the 1st gear (with clutch disengaged) – then slowly accelerates to 15 km/h in 4 s, cruises at constant speed for 8 s, brakes to a full stop in 5 s (manual: last 3 s with clutch disengaged), then stops for 21 s (manual: 16 s in neutral, then 5 s in the 1st gear).
- At 49 s, the car slowly accelerates to 32 km/h in 12 s (manual: 5 s in 1st gear, 2 s gear change, then 5 s in the 2nd gear), cruises for 24 s, slowly brakes to a full stop in 11 s (manual: last 3 s with clutch disengaged), then pauses for another 21 s (manual: 16 s in neutral, 5 s in the 1st gear).
- At 117 s, the car slowly accelerates to 50 km/h in 26 s (manual: 5 s, 9 s and 8 s in the 1st, 2nd and 3rd gears, with additional 2 × 2 s for gear changes), cruises for 12 s, decelerates to 35 km/h in 8 s, cruises for another 13 s, brakes to a full stop in 12 s (manual: 2 s change to the 2nd gear, 7 s in the 2nd gear, last 3 s with clutch disengaged), then pauses for 7 s (manual: in neutral with clutch engaged).
- The cycle ends on 195 s after a theoretical distance of 1017 meters, then it repeats four consecutive times. Total duration is 780 s (13 minutes) over a theoretical distance of 4067 meters, with an average speed of 18.77 km/h.
The combined fuel economy is calculated by a total consumption of urban and extra-urban cycles over the total distance (theoretical 11023 meters). The total test time amounts to 1180 s with an average speed of 33.6 km/h.
In order to get a car certified a test of the cars components must also be made, this list of parts include:Air Diverter Valve, Air/Fuel Control System, Air Injection Control Valves, Air Injection Pump, Camshaft Position Sensor, Canister Purge Valve, Carburetor or Fuel Injection System, Catalyst,Choke, Controlled Air Intake System, Coolant Temperature Sensor, Crankshaft Position Sensor, Diesel Particulate Control System, Distributor, EGR Control System Components, Electronic (Computer) Control System, Emissions Related Hoses, Tubing, Clamps, Belts, Fittings, Wiring, Connectors, Sensors and Switches, Evaporative System, Exhaust Gas Recirculation (EGR), Ignition Coil & Wires, Ignition Control Module, Intake Air Temperature Sensor, Malfunction Indicator Light (MIL), Mass Air Flow Sensor, Misfire Detection System, On-Board Diagnostic System, Oxygen Sensor, Positive Crankcase Ventilation, Power Train Control Module (Built-in test, BIT), Throttle Position Sensor, Vacuum Hose Connections
But thats not all, its not just good enough that these parts last during the test, all parts need to function just as well at an age of 5 years or 100’000 km as they did when they were brand new. For US certification the distance requirement is 150,000 miles.
Whats new for manufacturers is the Euro6 requirements that are coming up, these include changes to the test cycle but also introduce new items such as cold and time to warm-up. For example the exhaust cleaning installed must reach efficient operation temperature within 400 sec after starting up at -7°C but it must also work at these low temperatures.
ON-BOARD Diagnostics is a brand new thing for Euro 5b+ which is sort of an in-between stage from Euro 5 to Euro 6 regulations. What is basically means is that all cars need to carry a computer onboard that measures the exhaust and if the engine operates within the parameters required for its certification. If a component fails that causes the emissions to increase beyond the certification range, the drivers is notified that the car requires maintenance. The certification range measured by this system is the NEDC explained above.
The current regulations in effect is: Euro 5b+