Effect of Sampling Hose Length Variation on CO, HC Emission, and Exhaust Temperature Measurement in Motor Vehicles
Siti Shofiah (a*), Arief Novianto (a), Chairunisa Tenia Putri (a), Langgeng Asmoro (b,c), Muflihatun (d)

a) Diploma III Teknologi Otomotif, Politeknik Keselamatan Transportasi Jalan, Jl. Abdul Syukur No.17, Margadana, Kec. Margadana, Kota Tegal, Jawa Tengah 52143, Indonesia
b) Teknologi Rekayasa Otomotif, Politeknik Keselamatan Transportasi Jalan, Jl. Abdul Syukur No.17, Margadana, Kec. Margadana, Kota Tegal, Jawa Tengah 52143, Indonesia
c) Fisika, Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung, Jl. Ganesha No.10, Lb. Siliwangi, Kecamatan Coblong, Kota Bandung, Jawa Barat 40132, Indonesia
d) Fisika, Fakultas Matematika dan Ilmu Pengetahuan Alam, Universitas Jenderal Soedirman, Jl. DR. Soeparno No.61, Karang Bawang, Karangwangkal, Kec. Purwokerto Utara, Kabupaten Banyumas, Jawa Tengah 53122, Indonesia
*sitishofiah[at]pktj.ac.id

Abstract

Accurate measurement of exhaust gas emissions is fundamental to road vehicle safety compliance and environmental regulation. A key question for practical testing infrastructure is whether the physical length of the sampling hose connecting the vehicle^s exhaust pipe to the gas analyzer alters the measured concentrations of carbon monoxide (CO), hydrocarbons (HC), and exhaust temperature. This study investigated the effect of five hose length variants (2, 4, 6, 8, and 10 m) on these three emission parameters under controlled laboratory idle conditions, applying simple linear regression and normality diagnostics (Kolmogorov Smirnov and Shapiro Wilk). Physics based reasoning anchored in residence time analysis, Reynolds fluid flow theory, and the Hagen Poiseuille pressure-drop equation frames the experimental findings. Across all parameters and all trials, the coefficient of determination remained below 11% (R^2 < 0.11) and all p-values exceeded 0.05, confirming that the null hypothesis no significant effect of hose length in the 2-10 m range is retained. These results differ from prior studies on CO2/H2O analyzers and natural-gas pipelines, where hose length showed significant influence- the contrast is explained by the higher molecular inertness of automotive CO/HC, the lower adsorption affinity of these species compared with polar gases, and the relatively short transit times at typical sampling-pump flow rates. The findings provide practical guidance for emission-testing facility design: hose lengths between 2 and 10 m can be chosen on ergonomic or architectural grounds without compromising measurement validity.

Keywords: CO/HC emission measurement- sampling hose length- exhaust gas analysis- residence time- Hagen-Poiseuille- vehicle emission testing- fluid dynamics- regression analysis

Topic: Instrumentation and Computational Physics