Correlation Study of Exhaust Manifold - Lab Test Results vs Customer Fleet Results 2002-01-1317

The purpose of this study is to develop specifically a correlation between Exhaust Manifold Cracking Laboratory Test results and 150,000 mile customer fleet usage test results. The study shows that the exhaust manifold design meets the reliability requirements of 10 years or 150,000 miles, given 90^th percentile customer usage without an evidence of cracking or audible leaks. This correlation between the Lab Test and the customer Fleet results has been expressed as an acceleration factor. An acceleration factor is the ratio of how much quicker the engine dynamometer test ( i.e. Lab Test ) can accumulate the effect of customer usage over time versus the customers themselves. The acceleration factor is provided for useful life time period of 10 years or 150,000 miles. The recommended acceleration factor, determined in this study, is 38 to 1, comparing the engine dynamometer test ( i.e. Lab Test ) results to 150,000 mile modular truck customer fleet field results. Given 4054 hours of engine operation over 150,000 customer driven miles, 106 hours of the engine dynamometer test is equivalent to 150,000 miles of 90^th percentile customer operation. This study included both fabricated and cast iron exhaust manifolds. The study also includes the assumptions, derivations, and background information used to develop the exhaust manifold engine dynamometer test procedures. This study can be utilized as a reference whenever exhaust manifold engine dynamometer test is implemented. The content of this study may serve as a greater understanding of the reasoning behind the test procedures and enable accurate interpretation of the test results.