Development of a New Valvetrain Wear Test - The Sequence IVB Test

The study described in this paper covers the development of the Sequence IVB low-temperature valvetrain wear test as a replacement test platform for the existing ASTM D6891 Sequence IVA for the new engine oil category, ILSAC GF-6. The Sequence IVB Test uses a Toyota engine with dual overhead camshafts, direct-acting mechanical lifter valvetrain system. The original intent for the new test was to be a direct replacement for the Sequence IVA. Due to inherent differences in valvetrain system design between the Sequence IVA and IVB engines, it was necessary to alter existing test conditions to ensure adequate wear was produced on the valvetrain components to allow discrimination among the different lubricant formulations. A variety of test conditions and wear parameters were evaluated in the test development. Radioactive tracer technique (RATT) was used to determine the wear response of the test platform to various test conditions. To reduce test variability, the “Golden Stand” concept was introduced, requiring every Sequence IVB test stand to be identical and single-sourced. The final test conditions were selected, and lubricant discrimination, test repeatability and reproducibility were demonstrated in testing at two laboratories. The wear parameter selected for evaluation of lubricant performance was the intake lifter volume loss. The Sequence IVB valvetrain wear test was approved for precision matrix testing and is expected to be an integral part of the testing required to qualify passenger car engine oils for the ILSAC GF-6 category.