Although not specific to the 8051 , the "megasquirt" project is an open source fuel injection system that may be of interest.
It is a single injector design ,primarly for large US engines.

A major step up from that project would be a sequential multi injection system . There is an infineon article on controlling a 12 cylinder Formula 1 engine ,but it is written for the c16x.. If you were to use an infineon uC such as the 504,508 (with capcom6) it would be possible to port the project to a 4 cyl design.