numbers indicate engine rating in relation to MEP and/or
Pmax..1 is the first Tier II compliant engine
.2 is the fuel optimised Tier II compliant engine
.3 designates variable exhaust cam timing for ME-B engines
.4 designates design changes and increased Pmax of 5 bar /reduced SFOC
.5 extended layout diagram (MEP / Speed)
Different design changes is applicable for different versions.
AND there are several exceptions for above ’rules’