Calibration Process for SCR Only TIER4i Engine for Construction Equipment 2012-01-1954
The current legislation for industrial applications and construction equipment including earthmoving machines and crane engines allows different strategies to fulfill the corresponding exhaust emission limits. Liebherr Machines Bulle SA developed their engines to accomplish these limits using SCRonly technology. IAV supported this development, carrying out engine as well as SCR aftertreatment system and vehicle calibration work including the OBD and NOx Control System (NCS) calibration, as well as executing the homologation procedures at the IAV development center. The engines are used in various Liebherr applications certified for EU Stage IIIb, EPA TIER 4i, China GB4 and IMO MARPOL Tier II according to the regulations “97/68/EC”, “40 CFR Part 1039”, “GB17691-2005” and “40 CFR Parts 9, 85, et al.” using the same SCR hardware for all engine power variants of the corresponding I6 and V8 engine families.
This paper covers aspects of the different emission regulations as well as the different engine applications with their individual load collectives and restrictions. Special emphasis is placed on the SCR hardware and its calibration. For the different applications of this modular system many different exhaust system layouts with multiple ducting variants and differing flow behaviors respectively were required. Therefore special attention has to be given to the monitoring functionalities and their calibration in order to allow a robust system behavior for the different applications with their individual exhaust ducting. The calibration process and the experiences gathered within this project are described. This includes a description of the calibration process of engine P&E, the SCR system as well as monitoring and vehicle calibration. While the US and EU certification is carried out using off-highway specific emissions cycles, the Chinese homologation requires to use the on-road specific cycles (ETC/ESC) and the corresponding OBD. Additionally an overview of the challenging vehicle testing of these large machines is given.