The present wording on implementing regulation on type-approval
of motor vehicles and engines with respect to emissions from
heavy-duty vehicles in Europe (e.g., Euro VI requirements)
describes the procedure to determine gaseous emissions from on-road
measurements using Portable Emissions Measurement Systems
(PEMS).
The gaseous emissions to be measured according to the PEMS
protocol includes carbon monoxide (CO), total hydrocarbons (THC)
and nitrogen oxides (NOx) for diesel engines and with
the addition of methane (CH₄) for gas engines. Measurement methods
of particles are at this stage under development. Emission data
from on-road testing can be used for calculation of In-service
Conformity (IsC) pass/fail criteria but also for establishing local
emission factors for specific routes.
The procedure for the measurement is described in detail in the
regulation. During on-board measurement, emission sampling,
measurement of the exhaust parameters and recording of the engine
parameters as well as ambient data shall continue throughout the
normal in-use operation of the vehicle, i.e., driving conditions
should correspond to actual real-life conditions.
Certification testing of HD engines is carried out in a very
controlled laboratory environment by testing an engine as a
standalone unit. Results from real-life emission testing might thus
be very different from testing according to the certification
procedure. This paper will present the impact on emissions from
four heavy-duty vehicles with regard to factors such as ambient
temperature, engine coolant temperature as well as vehicle load. It
will also highlight the variation in emission results with regard
to various driving conditions using different calculation
methods.