Key Technical Demands

TOP TIER™+ standards are based on fuel performance in a series of new GDI-specific tests that better enable evaluation against real-world operating conditions. The following covers the principal performance areas. Confirm all limits and test details against published TOP TIER™+ program documentation as requirements are finalized.

Proposed Performance Requirements

Performance Area	Test Focus	TOP TIER^™+ Requirement	vs. TOP TIER™ (2004)
GDI Injector Keep-Clean	Prevention of deposit formation on GDI injectors	Pass GDI-specific injector keep-clean test	New GDI test - not addressed in original standard
GDI Injector Clean-Up	Removal of existing deposits from dirty GDI injectors	Demonstrate measurable deposit reduction on pre-dirtied injectors	New clean-up requirement - original standard had no aged-engine test
PFI Intake Valve Deposits	Intake valve cleanliness in PFI context	Existing TOP TIER™ IVD limits maintained	Retained from current standard
Combustion Chamber Deposits	Deposit control within combustion chamber	Enhanced deposit control performance	Tightened from current standard
Injector Tip Deposit Control	Deposit accumulation at GDI injector tip	Defined tip deposit performance limit	New requirement specific to GDI architecture
Fuel Economy Contribution	Measurable contribution to engine efficiency	Efficiency improvement demonstrated vs. reference fuel	New efficiency performance requirement

TOP TIER™+ Fuel Specification