According to Table 4, for both fuels, it could be seen that
at idle speed NOX emissions were a lot lower than that at
other modes; whereas at 50 km h−1, remarkably high NOX
concentrations were observed, up to about 70 mg/km. The
combustion process at idle speed can only produce a lower
flame temperature and at high speed get a higher temperature,
which are the reason of the above results. At the same driving
mode, the addition of ethanol into gasoline did not influence
NOX emissions.