An internal combustion engine (10) comprising: a piston (12) arranged to reciprocate within a cylinder (14); an adjustable volume induction chamber (50) communicating with the cylinder (14); an air inlet port (30) communicating (42) with the induction chamber (50), the air inlet port (30) being connectable, in use, to a pressurized air supply (38); an air inlet valve (32) configured to selectively open and close the air inlet port (30); and a fuel injector (70) communicating with the induction chamber (50), wherein the valve (32) and fuel injector (70) are together configured, in use, to deliver a charge comprising a fuel-air mixture into the induction chamber (50).