A system for introducing fuel into the combustion chamber of an internal combustion engine which includes at least one piston reciprocating in a cylinder with a cylinder head closing the top of the cylinder forming a combustion chamber between piston and head. At least one intake valve and one exhaust valve are provided in the cylinder head. One or more fuel injectors communicate through the sidewall of each of the engine cylinders for injecting fuel during the piston intake stroke while the top of the piston is below the injection site. The fuel injector may be any suitable injector, typically of a low pressure type. The fuel injector is oriented to direct a spray of fuel droplets in the direction of the cylinder head and/or the closed exhaust valve to speed droplet evaporation and cool the exhaust valve. Engines using this system also have increased tolerance of low octane fuel and improved emission characteristics.