Abstract

Gasoline components play a major role in formation of deposits on intake system and combustion chamber thereby affecting engine performance and emissions. To meet the stringent emissions standard and performance of present day engine technology, it is essential to improve the fuel quality. Improvements in fuel quality are achieved at refinery level through reduction in sulfur, benzene and olefins content, enhancement of octane number etc. Addition of tailor made additive packages termed as multi-functional additives (MFAs) are resorted to for further improvement in engine performance and emission reduction. A large number of engine tests have been carried out on Mercedes Benz M 111 engine as per CEC F-20-A-98 test method in order to evaluate performance related to intake valve deposit (IVD) and combustion chamber deposit (CCD) forming tendency using gasoline with varying compositions, ethanol blended gasoline and additised gasoline. Multi functional additives containing mainly detergents of different chemistry reduce the intake valve deposits with increase in combustion chamber deposits. The deposit formation varies with composition of the fuel and chemistry & the treat rate of the additives used. It has also been observed that the IVD and CCD values of gasoline increased with ethanol and olefins content. However, no definite relationship could be discerned between IVD and CCD values for the samples tested except for samples with limited complexity.

In order to get further insight into the effect of deposits buildup on emissions, exhaust emissions were measured at intermittent of tests (0 hr, 20 hr, 40 hr and 60 hr) for a gasoline sample and the gasoline sample treated with the same treat rate of four different additives. Carbon monoxide (CO) emissions increased with deposits formation and hydrocarbons (HC) emissions increased rapidly for certain period of deposit built-up and then stabilized. Therefore, tailor-made additive package is essential to add in gasoline in order to maintain the performance and emission of new generation technology engines.

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