A TECHNIQUE FOR DETERMINING THE OCTANE NUMBER REQUIREMENTS OF COMMERCIAL VEHICLES

Despite the size and importance of the fleet market, refiners have little information on the antiknock requirements of commercial vehicles. Considerable interest has been displayed in obtaining reliable data in this area.

Some road survey data have been obtained in the past; however, truck engines are more prone to high-speed knock due to today’s more sensitive fuels and higher governed speeds. Knock under these conditions is more damaging and cannot be heard due to the masking effect of the high level of vehicle noise on the road.

A chassis dynamometer technique has been developed to overcome this noise barrier and thereby provide realistic octane requirement data. Data obtained with this technique on commercial-type fuels were used to construct what is described as an “octane requirement map”. This map extends the usefulness of the data and is a unique and effective means of expressing octane requirements, particularly how requirements are related to the sensitivity of the fuel. The map is also used to describe a new concept in determining relative engine severity.