Abstract Effectiveness of the particles issued from diesel engines that are mainly soot, on human healthiness by international agency of cancer made in 1988 has shown that, the Particulate Material (PM) will increase the probability of suffering to cancer. In this work first of all the naturally aspirated diesel engine of type OM314 from city driving motorbus and truck vehicles (Khavar) has been introduced. Then it is converted to limited pressure turbocharged OM314 Diesel engine. At the final stage the injectors pressure have been elevated from 200 bars to 240 bars with the purpose of decreasing the soot emission. In each stage in order to investigate the soot contents, the engine has been tested under ECE-R49, 13 mode standard test. Results show that the naturally aspirated engine does not cover the standard Euro I. The turbocharged OM314 engine catches the Euro I standard with specific soot emission 35% less then the naturally aspirated engine maybe due to reduction in ignition delay and better soot burnout process. The elevating of the injection pressure makes a better mixing of fuel to air and results an amount of specific soot 21% less than Euro I, but it does not cover the Euro II standard.

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