A method for controlling a fluid quantity in an internal combustion engine is provided for an internal combustion engine having an engine shaft and an operation cycle that includes at least one intake phase, one proportioning phase, one combustion phase in a combustion chamber of the engine, an engine intake system, an exhaust system having a duct for removing fluid from the combustion chamber, and a timing system to control an opening and a closing of the exhaust system duct. The method includes keeping an exhaust valve open for an adjustable time length in an initial part of the intake, proportioning and compressing phase and entering an amount of fuel corresponding to the amount of air remaining in the compression chamber after closing the exhaust valve in a subsequent part of the intake, portioning and compression phase.