© copyright FACULTY of ENGINEERING ‐ HUNEDOARA, ROMANIA 177 1. S. O. ISMAILA, 2. B. O. BOLAJI, 3. O. R. ADETUNJI, 4. N. O. ADEKUNLE, 5. T. A. YUSUF, 6. H. O. SANUSI ON VEHICULAR EMISSIONS OF PETROL AND DIESEL ENGINES 1-4. DEPT. OF MECHANICAL ENGINEERING, FEDERAL UNIVERSITY OF AGRICULTURE, ABEOKUTA, OGUN STATE, NIGERIA 5. DEPT. OF MECHANICAL ENGINEERING, UNIVERSITY OF AGRICULTURE, MARKUDI, BENUE STATE, NIGERIA 6. DEPT. OF AGRICULTURAL ENGINEERING TECHNOLOGY, COLLEGE OF AGRICULTURE AND ANIMAL TECHNOLOGY, BAKURA, ZAMFARA STATE, NIGERIA ABSTRACT: The rise in the number of vehicles in Nigeria has significantly increased the vehicular emissions in the country especially in towns and cities. Some studies in the area of vehicular emissions of petrol and diesel engine vehicles concentrating on CO and CO 2 existed. This study in addition to CO and CO 2 emissions characteristics attempt to study the O 2 emission of both types of engines. The analysis of data conducted on the emissions of petrol and diesel engine vehicles using a two-sample equal variance one-tail t-test showed that there were significant differences between the data of CO for the two types of engines (p=4.86x10 -6 ), for CO 2 (p=1.77x10 -14 ) and O 2 (p=1.65x10 -19 ). The CO and CO 2 emissions were consistently higher for petrol engines as compared to diesel engine vehicles while O 2 was consistently lower. Pearson Correlation Coefficient for age and CO of petrol engine vehicles showed that there was very low negative correlation (r= -0.27). Same test showed that there was no correlation between age and CO 2 (r=0.00) as well as age and O 2 (r= -0.02). Similarly, for diesel engine vehicles there was very low positive correlation between age and CO (r= 0.29), no correlation between age and CO 2 (r= -0.03) as well as a very low positive correlation between age and O 2 (r= 0.25).These results suggest that the rise in manufacture and distribution of diesel engine vehicles can be further strengthened if its higher emission of O 2 is considered in addition to lower emissions of poisonous CO and green house gas CO 2 . It may also be stated that emissions from vehicles irrespective of type of type of engine is independent of age. KEYWORDS: Vehicle Emissions, Petrol Engines, Diesel Engines INTRODUCTION The number of vehicles in Nigeria has increased substantially in the last 10 years and as such significantly increases vehicle emissions that pollute the air. According to Karlsson (2004) vehicular emissions pollute the air and must be controlled to alleviate the problems that may be associated with such pollution. Okoko (2005) observed that journeys of short duration lead to incomplete combustion of fuel and thus vehicles run less efficiently. This may be applicable to Nigerian cities and towns where traffic hold ups hold sway. Bull (1991) had observed that due to congestion and traffic hold ups, vehicle emissions increase much faster than the actual growth in the number of vehicles. Transportation Research Board (2008) buttressed the observation of Bull (1991) and found that for the same amount of time in operation, vehicles in idling condition produce higher average concentrations of Carbon Monoxide (CO), Nitric Oxide (NO), Nitrogen dioxide (NO 2 ) and Sulphur dioxide (SO 2 ). Vehicle emissions include volatile organic compounds, Nitrogen Oxides, lead and Carbon Monoxide that have adverse effects on natural environment, human health, agricultural productivity and natural ecosystems as noted by Bolaji and Adejuyigbe (2006). Also, Dewaram (2002) stated that hydrocarbons present in the exhaust particularly in vehicles with poor combustion cause respiratory problems. Once these fumes are emitted into the atmosphere, Zannetti (1992) opined that the pollutants undergo mixing or diffusion, the degree of which depends on topographic, climatic and meteorological conditions. The effects of vehicle emissions on humans and other natural ecosystems led to the study on vehicle emissions and how they can be controlled. Frey and Zheng (2002) noted that vehicle emissions are dependent on vehicle design, operation, maintenance and fuel composition. Emissions from cars are greatest when an engine is cold. On a cold day a petrol car may take up to ten kilometres to warm up and operate at maximum efficiency, whereas a diesel car may only take five kilometres. Therefore diesel cars will produce less unburnt fuel during a cold start, which will result in fewer emissions of carbon monoxide and hydrocarbons. This would mean that diesel cars would make a significant impact on air quality in urban areas where