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Abstract. Bi-fuel-Gasoline/LPG system has been effectively and efficiently used in gasoline vehicles with less pollutants emission. The motorcycle tested was a used Honda AirBlade i110 -fuel injection type. A 3-litre LPG storage tank, an electronic fuel control unit, a 1-mm LPG injector and a regulator were securely installed. The converted motorcycle can be started with either gasoline or LPG. The safety relief valve was set below 48 kPa and over 110 kPa. The motorcycle was tuned at the relative rich air-fuel ratio () of 0.85-0.90 to attain the best power output. From dynamometer tests over the speed range of 65-100 km/h, the average power output when fuelling LPG was 5.16 hp; dropped 3.9% from the use of gasoline91. The average LPG consumption rate from the city road test at the average speed of 60 km/h was 40.1 km/l, about 17.7% more. This corresponded to lower LPG's energy density of about 16.2%. In emission, the CO and HC concentrations were 44.4% and 26.5% lower. Once a standard gas equipment set with ECU and LPG injector were securely installed and the engine was properly tuned up to suit LPG's characteristics, the converted bi-fuel motorcycle offers efficiently, safely and economically performance with environmental friendly emission.

Problem statement: Though ethanol and gasohol are proved to be used as alternative fuels in vehicles, 4-stoke motorcycles used nationwide mainly consumed gasoline 91/95. Approach: The motorcycle tested, the used Honda Wave125 model, was properly tuned at the rich relative air-fuel ratio (λ) 0.85, which theoretically gave the maximum power output. For the use of E100, the engine required richer air-fuel mixture condition, the main nozzle and idle nozzle sizes were therefore increased from the sizes used for gasoline91; by 21.4% from 0.78 mm for the main nozzle and 76% from 0.35 mm for the idle nozzle. Due to having three times higher in heat of vaporization, the stronger current ignition coil was used instead. This eased the engine starting without any trace amount of gasoline. The ignition timing was advanced by about +9O crank angle to suit E100's high octane number of 107. Results: The performance test results of E100 on dynamometer showed that the maximum power output was 9 hp@7428 rpm and the maximum torque was 11 Nm@4728 rpm. Comparing to the use of gasoline91, the engine performance decreased 12-15% over the speed range of around 4000-8000 rpm. From the road tests; city road test and long driving test, at the average speed of 60 km h −1 , the average consumption rate of E100 was about 25-28% more. The calculated fuel conversion efficiency of E100 was 38.2% higher. For emission measurements when using E100, the concentrations of CO and of HC were 3.14 vol % and 2143 ppm. Those were higher than in the exhaust of the use of gasoline91 but below the regulations which required <4.5vol % for CO concentration and <10,000 ppm for HC concentration. Though the NOx concentration in the exhaust of all tests was not measured, high NOx concentration was observed in the lean mixture at λ >1.0 condition. Since a particular instrument was not available, aldehyde concentration in the E100's emission was not measured. Conclusion: It clearly confirmed that E100, 95.5 vol % ethanol, can be effectively used as an alternative fuel in used 4-stroke motorcycles whose carburetors were purposely designed for the use of gasoline91. If the engines were properly tuned up and modified to best suit the E100's characteristics while maintaining the compression ratio, the motorcycles performed as efficient as fueling gasoline91.

From the test study of the use of biodiesel B10 in a diesel pick-up truck with an engine size not over 2500 cc, it showed that biodiesel B10 can be effectively used as an alternative fuel giving low polluted emission. On dynamometer performance test of the Isuzu TFR 2500 Di pick-up truck used over 200,000 kilometers, it resulted that the maximum power output from the use of diesel was 60.9 hp@3,630 rpm whereas from the use of biodiesel B10 was 58.1 hp@3,700 rpm which was about 4.6% lower. Considering the heating value of diesel of 35,970 kJ/l, it was 8.4% higher than that of the pure biodiesel (32,940 kJ/l). Since biodiesel B10 is a mixture of 10% pure biodiesel and 90% diesel fuel, and the molecular structure of biodiesel contains 11%wt oxygen gives better combustion. However, biodiesel was more viscous compared to diesel at the same fuel injection pressure of 180 kgf/cm2, therefore, the fuel nozzle injector was changed to a 5-hole nozzle from the original 4-hole nozzle for better fuel spray and atomization in the combustion chamber. The maximum power output of 58.6 hp@3,685 rpm was achieved but the fuel consumption rate and soot emission were lower. Comparing the road test results at the average speed of 90 km/h, the average consumption rate of biodiesel B10 was 16.4 km/l which was about 5.2% higher than that of diesel of 17.3 km/l. When changing to 5-hole fuel injector, the average consumption rate of biodiesel B10 was 18.4 km/l, about 12.2% saver than from the original 4-hole nozzle use. Similarly the average consumption rate of diesel when using the 5-hole nozzle injector was saver to 18.6 km/l. It clearly provided better fuel atomization in the combustion chamber. From the random emission measurements, it showed that there was 33.7% soot from using biodiesel B10 which was lower than the use of diesel of 34.2% for 4-hole fuel injector, and decreased to 31.2% when switching to the 5-hole fuel injector. Keywords: biodiesel, B10, alternative fuel, diesel pick-up truck, fuel nozzle injector