Abstract for presentation at 14th IUAPPA World Congress

Steady-state and transient chassis dynamometer measurements have been made of exhaust emissions from two in-service commercial buses fuelled with diesel-biodiesel blends. Blends of 20% and 40% biodiesel were used. The biodiesel was processed from tallow and met the New Zealand Standard 7500 for biodiesel fuels.
Measurements include fuel consumption and exhaust emissions of CO₂, CO, THC, NO_x and PM. The steady-state measurements were taken at operating conditions corresponding to 3 engine speeds at full rack and 3 partial load/power points at a single engine speed. The transient tests were rapid accelerations to 80 km/h from standstill, representing typical acceleration of the bus on a flat road.
Exhaust sampling was carried out using a full flow dilution tunnel with a constant volume sampler (CVS) system. Gaseous emissions were measured using laboratory grade emissions analysers including hot NO_x and THC. Particulate samples were re-diluted using partial sampling off the full flow dilution system prior to measurement using gravimetric filter weighing and light scattering photometry.
The results were not consistent between the two buses, which suggests that the different technology responds differently to the fuels. However, in general, reductions in all major emissions species were found, with no conclusive change in power output or fuel consumption between the different fuel blends.