Biodiesel in present trend is important due to depletion of non-renewable resources. The shortage of fossil fuels brings usage of bio diesel into limelight. Therefore usage of bio diesel is preferred than usage of conventional diesel as the properties of both are almost same. A lot of research has undergone on bio diesel and doesn't show any significant variation in emissions compared to conventional diesel. Due to high emissions of harmful gases global warming increases which is not preferable. In this paper Flax seed is used for bio diesel preparation which is abundantly available in mountainous areas and cooler regions. Flax seed commonly known as lin seed has binomial name Linum usitatissium. In this process the oil is transesterified using methanol to produce methyl esters in presence of base catalyst. Methanol is mixed with flax seed oil in the ratio 1:5 and 0.5 to 5% base catalyst is added. This mixture is constantly stirred at 55?C.

Due to high viscosity it is difficult for biodiesel to mix with air in the combustion chamber and results in increase of emissions . As the fuel injection is advanced by change in crank angle up to certain extent in a VCR engine, the time available for mixing fuel with air is increased ensuring increased mixing of fuel with air, and By increasing the compression ratio the pressure in combustion chamber increases which helps high viscous fuel to mix completely, due to high temperature because of the high pressure in the combustion chamber the combustion characteristics of charge increased results in lowering the engine emissions. The above tests were conducted using conventional diesel, and different proportions of blends of bio diesel and results were compared by varying crank angle and compression ratios.