Injection timing

Injection timing is the crank angle at which fuel injection begins, referenced to top dead center. It sets where combustion occurs in the cycle and trades peak firing pressure and NOx against fuel consumption: advancing injection raises peak pressure and NOx but can lower specific consumption, while retarding it does the reverse, which is the basis of NOx Tier control under MARPOL Annex VI Reg 13. In camshaft engines timing is fixed by cam geometry, modified only by a VIT rack. Electronically controlled engines such as the MAN ME and Sulzer RT-flex set timing in software per cylinder and per load, allowing continuous optimization across the operating range.