4.4.6.1 Minor adjustments and modifications in
accordance with the engine group concept are allowed after pre-certification
or final test-bed measurement within an engine group upon agreement
of the parties concerned and approval of the Administration, if:
-
.1 an inspection of emission-relevant engine parameters
and/or provisions of the on-board NOx verification procedures
of the engine and/or data provided by the engine manufacturer confirm
that the adjusted or modified engine complies with the applicable
NOx emission limits. The engine test bed results on NOx emissions
should be accepted as an option for verifying on-board adjustments
or modifications to an engine within an engine group; or
-
.2 on-board measurement confirms that the adjusted
or modified engine complies with the applicable NOx emission
limits.
4.4.6.2 Examples of adjustments and modifications
within an engine group that may be permitted, but are not limited
to those described below:
-
.1 for on-board conditions, adjustment of:
- injection timing for compensation of fuel property differences,
- injection timing for optimization of maximum cylinder pressure,
- fuel delivery differences between cylinders
-
.2 for performance optimization, modification
of:
- turbocharger,
- injection pump components,
- - plunger specification
- - delivery valve specification
- injection nozzles,
- cam profiles,
- - intake and/or exhaust valve
- - injection cam
- combustion chamber.
4.4.6.3 The above examples of modifications after
a test-bed trial concern essential improvements of components or engine
performance during the life of an engine. This is one of the main
reasons for the existence of the engine group concept. The Administration,
upon application, may accept the results from a demonstration test
carried out on one engine, possibly a test engine, indicating the
effects of the modifications on the NOx level which may
be accepted for all engines within that engine group without requiring
certification measurements on each engine of the group.