1994-10-01

The Effect of Unleaded Gasoline Formulation on Antiknock Performance 941862

The knock behavior of two groups of unleaded gasolines, each of which includes three fuels with different chemical compositions but comparable standard octane numbers, has been analyzed using a mass-produced engine.
The aim of the work was to point out possible inconsistencies between the standard octane numbers of the fuels and their knock behavior in mass-produced engines.
The fuels of the first group had R.O.N.s and M.O.N.s very close to the minimum values required by European Community regulations (95 and 85, respectively), whereas the fuels of the second group had higher R.O.N.s and M.O.N.s (about 100 and 87.5, respectively).
One of the tested fuels in the first group was a typical European unleaded gasoline, the other gasolines had higher olefin or aromatic contents. An increase of the aromatic content has not shown appreciable differences between the expected knock behavior of the fuel from its standard octane numbers, and its performance on the mass-produced engine. On the contrary, a higher olefin content has revealed a remarkable difference.
The second group was made up of gasolines obtained by mixing base fuels, similar to typical European unleaded gasoline, with MTBE, methanol and ethanol. Only MTBE has shown quite a good correspondence between the predicted and actual behavior, while alcohols, despite quite a good correlation at low speed, have revealed discrepancies in the medium and high speed range.

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