PARTICULAR PROBLEM FOR PHEV TESTING
The PHEV is quite new technology from stand of view of
regulatory side. We want to describe problem of concern
by reason of new technology of PHEV at the last
sections of this paper. In the case of PHEV emissions
measurement, there is a possibility that ICE is running
until the test cycle is very short duration. The CVS-bag
method[3] is regulated as the measurement method for
emission and fuel efficiency. In this method, all of the
exhaust gas is diluted and collected by Constant volume
Sampler (CVS), and then the bag is filled during the
whole of a test cycle. If ICE running is only a small
portion of a test cycle, exhausted gas portion in the filling
bag is very small. Actual dilution factor in the bag is
large. In order to achieve a dilution factor of over 20, it is
hard to get reliable measurement value due to limitation
of analyzer resolution and calibration gas accuracy. We
have to be aware of this possibility of significant error in
the conventional CVS method. We have to prepare
alternative test method to replace CVS-bag method in
such cases. One a promising measurement technique is
the dilution modal measurement method. The dilution
modal measurement does not use bag filling, continues
gas concentration measuring after CVS dilution, and
then analyzes modal approach. This method does not
affect such an over dilute due to PHEV operation.