Abstract: A method for fouling an injector of a gasoline direct injection engine, includes the steps of operating the direct injection engine on at least a first stationary engine mode which is defined by a pre-established engine load and a pre-established engine speed. Both the pre-established engine load and the speed are within 35% and 65% of their maximum values, this at least first stationary engine mode being characterized by high particulate matter generation. The direct injection engine is operated on the at least first engine mode for less than ten hours. A method for evaluating the fouling effect of a gasoline formulation in a gasoline direct injection engine uses the above-described fouling method.

Abstract: The invention relates to a liquefied petroleum gas direct injection engine (100) comprising at least one cylinder comprising a combustion chamber (1) having a spark plug (2), one or more intake valve or valves (4) and one or more exhaust valve or valves (5). The LPG engine (100) further comprises at least one injector (6) for injecting liquefied petroleum gas in liquid state directly into the combustion chamber, the LPG being injected at a pre-established pressure value; a high pressure pump (9) for feeding pressurized liquefied petroleum gas to at least one injector (6); and an electronic control unit (13) configured to operate the at least one injector (6) for injecting the LPG during a specific injection time period or periods such that a predefined target mass of liquefied petroleum gas is injected, and between 360° BTDC and 60° BTDC of the engine cycle. The invention also refers to a control method of a liquefied petroleum gas direct injection engine (100).