Engine wear has been a concern since the internal combustion engine was developed. As gasoline powered engines became mainstream and vehicle manufacturers started selling them in the thousands, then millions each year, an entire industry was established around the testing of lubricants for, among other things, wear protection.
SwRI is part of this industry, testing lubricants through engine Sequence tests to qualify them for lubricant standards. Along with this industry work, SwRI has also developed research capabilities to assist its lubricant, additive, and OEM clients in understanding wear phenomena in engines. As part of this, SwRI developed Radioactive Tracer Technology (RATT®) for real-time engine wear evaluations. This involves taking engine components and activating them using either bulk or surface layer activation using radioactive sources. This changes some of the material of the engine parts to isotopes, which can be detected by radioactive detectors. Once the engine is assembled, the engine components wear during engine operation and these isotopes become part of the wear debris in the oil. The level of radioactive particles present in the oil due to wear of the irradiated engine components is then detected and the strength of the signal for each isotope is correlated with the mass of wear material in the oil.
The aim of this project was to leverage the use of an already irradiated engine with useful life remaining and further understand and enhance the method.
In this project a 2.0L Ecoboost TDI engine with activated valvetrain, top piston rings, liner, and turbo thrust plate was taken and several conditions investigated to further understand the technology and guide future RATT engine wear testing programs. The engine was run using three different viscosity grade oils (SAE 5W-30, 0W-16, and 0W-08) and three SAE 5W-30 oils with different levels of wear protection (high, medium, and low). Several different engine cycles were used, as described in the report, allowing five distinct conclusions to be drawn from the work.
120 seconds were found to be the most statistically accurate sample time for RATT engine wear measurements.
The effect of engine tear down and rebuild on differences in pre- and post-test wear did not have a significant effect. Results showed that a 4-hour post build run-in is enough to bring the engine back to original wear rates.
Results showed little evidence to support concerns that severe engine cycles could influence engine wear rates beyond that severe cycle.
Two engine cycles were operated, hot and cold, which showed camshaft wear could be produced and measured on this engine. It was also observed that, although the IVA and IVB engine tests are cold temperature tests, significantly more wear was observed during the hot engine cycle.
The engine ran successfully on SAE 0W-08 lubricant and lower wear was measured than anticipated. The recommended lubricant viscosity for this engine is SAE 5W-30.
This work has maintained confidence in the RATT engine wear technology and will guide future RATT engine wear testing programs undertaken at SwRI.