(a) For Phase 1 engines, the manufacturer must select, from each engine family, a test engine that the manufacturer determines to be most likely to exceed the emission standard. For Phase 2 engines, the manufacturer must select, from each engine family, a test engine of a configuration that the manufacturer determines to be most likely to exceed the HC+NOX (NMHC+NOX) Family Emission Limit (FEL), or HC+NOX (NMHC+NOX) standard if no FEL is applicable.
(b) The test engine must be constructed to be representative of production engines. [60 FR 34598, July 3, 1995, as amended at 64 FR 15239, Mar. 30, 1999]