Accurate exhaust mass flow measurement is critical for Real Driving Emission
(RDE) testing; however, it is particularly challenging for motorcycles due to
variations in chemical composition, strong pulsations and even reverse flow
effects at low engine speeds. Traditional differential pressure-based flow
meters often struggle under these conditions, particularly in low-speed and
low-load operation. This study evaluates the feasibility and accuracy of an
Annubar-based exhaust flow meter (EFM) designed to address these challenges by
means of assessing eight motorcycles with single-, two-, and four-cylinder
engine configurations. The EFM performance is evaluated via correlation analysis
with laboratory-grade reference instruments and engine control unit (ECU) data.
Additionally, systematic effects such as pulsation behavior, spectrogram
analysis, and the influence of engine load and speed are investigated.
The results demonstrate a strong correlation between EFM and reference
measurements, indicating the EFM potential as a viable exhaust mass flow
measurement solution. However, systematic deviations were observed, particularly
at low engine speeds and loads, where pulsation effects caused oscillatory
measurement behavior. These deviations stem from the interaction between
engine-induced pulsations and the EFM response characteristics. To mitigate
these effects, advanced filtering techniques and engine-aware compensation
strategies, leveraging engine RPM and load data, are proposed to enhance
measurement stability and accuracy. These improvements could make EFMs a more
reliable tool for motorcycle RDE assessments, enhancing real-world emission
testing methodologies.