PREDICTION OF C9 ENGINE PERFORMANCE ON A D6R DOZER BASED ON WEAR OF PISTON RINGS, MAIN JOURNALS, CRANKPINS, AND CYLINDER LINERS

This study develops a technical-life prediction model for the Cat C9 engine installed on a D6R dozer using teardown inspection data. The dataset comprised 20 inspection sheets; after duplicate checking, 18 independent engines remained, with 10,651-20,991 operating hours. The analyzed variables included the end gaps of three piston-ring types, main-journal diameter, crankpin diameter, and cylinder-liner diameter. Damage was normalized against the technical limits stated in the inspection records, and Taguchi signal-to-noise ratios under the “smaller-is-better” criterion were calculated across repeated measurement locations. Linear regression between mean dimensions and operating hours was used to determine threshold-crossing times. The predicted threshold lives of piston rings 1, 2, and 3 and the cylinder liner were 9,896, 10,005, 9,926, and 10,254 h, respectively, substantially shorter than those of the main journals (20,393 h) and crankpins (24,722 h). The cylinder liner (-3.084 dB) and piston rings (-0.996 dB) had the lowest mean S/N values, confirming that these two component groups govern the overhaul interval. Under the weakest-link principle, system life was estimated at approximately 9,900 h; a proactive inspection window of 9,500-10,000 h is recommended for operating conditions similar to those represented by the sample. The method provides a quantitative basis for maintenance planning while explicitly treating the Taguchi S/N metric as a retrospective application rather than a substitute for a controlled orthogonal-array experiment.