The purpose of the fuel-mixture formation, is that, particularly in the petrol engine, the fuel should be mixed with the intake-air in certain proportions and is burnt with the best possible energy output and environmental compatability.
In the vacuum intake petrol injection and the side combustion chamber method (Diesel engine), the fuel is injected as a fine spray, into the intake-air. In the case of the direct injection, the fuel is sprayed through a nozzle, directly into the combustion chamber, this method is found in all Diesel- and direct petrol injection engines. This is why it's called 'internal mixture formation', as opposed to the 'external mixture formation' in vacuum intake injection engines. 06/10
