Air & Transportation

Future Policy for Motor Vehicle Exhaust Emission Reduction(second report) - Chapter 4

Reduction Measures for Fuel Evaporative Emissions from Gasoline Motor Vehicles

(1) Reduction measures for fuel evaporative emissions and enforcement time

With a view to further reducing hydrocarbons emitted as fuel evaporative emissions from gasoline motor vehicles, it is appropriate to adopt a new test procedure as indicated in Attached Table 3. The new test will examine fuel evaporative emissions (Diurnal Breathing Loss: DBL) discharged when ambient temperature acts as the heat sources when a motor vehicle is parked for long periods of time, including changes from day to night. This new method must be employed in addition to the previous fuel evaporative emissions test (Hot Soak Loss: HSL) that considered emissions when motor vehicles themselves acted as the heat source when parked.

In this case, it is advisable to set the permissible limit at a level of 2.0 g/test as with the current testing procedure. For accurate measurements of emissions from fuel storage and supply systems, it is recommended that the measurements be conducted through the enclosure method employing the SHED facilities (Sealed Housing for Evaporative Emission Determinations) where the temperature can be controlled.

In respect to the quality of fuel to be used for the test, it is appropriate to prescribe the value for Reid Vapor Pressure (RVP) at a narrower range than the JIS Standard (44 to 78 kPa). Therefore, it is advisable to determine the value within a year while taking into consideration the trend of actual values in the markets.

Moreover, with regard to the introducing time of this test procedure, it seems proper to introduce this new testing procedure at the same time as he new target values described in Paragraph (1). In other words, it is recommended to introduce the test procedure by the end of 2000 for passenger cars and light-duty motor vehicles, by the end of 2001 for medium-duty motor vehicles and heavy-duty motor vehicles, and by the end of 2002 for mini-sized trucks.

(2) Medium-term and long-term subjects for reduction of fuel evaporative emissions

In order to further reduce fuel evaporative emissions, it is necessary to conduct investigations into the actual condition of fuel evaporative emissions. Furthermore, taking into consideration the reduction caused by the introduction of the new test procedure for fuel evaporative emission as indicated in Paragraph (1), it is imperative to review the necessity of extending the measurement time of DBL; the necessity of introducing a test procedure anticipating the fuel evaporative emissions (running loss: RL) caused by the heat of motor vehicle themselves during running and the heat radiating from the road in the case of the measures for gasoline motor vehicles; and the necessity of RVP reduction in the case of the measures for quality of fuel.

Furthermore, in respect to reduction measures for fuel evaporative emissions during refueling, etc. of motor vehicles, it is mandatory to review the necessity of these measures while aiming at grasping the actual emission state on the medium- and long-term basis.

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