1998-05-04

A Statistical Review of Available Data Correlating the BMW and Ford Intake Valve Deposit Tests 981365

A 100-hour engine dynamometer test for intake valve deposits (IVD) which uses a Ford 2.3L engine was developed by the Coordinating Research Council (CRC). Recently, this test has been approved by the American Society for Testing and Materials (ASTM) as Test Method D 6201-97. Since this test offers improvements in test variability, duration, and cost, it is expected to replace ASTM D 5500-94, a 16,000-km vehicle test run using a BMW 318i, as the key performance test for the Certification of Gasoline Deposit Control Additives by the EPA Final Rule.
As a step in the replacement process, a correlation between valve deposit levels for the CRC 2.3L Ford IVD test and ASTM D 5500 BMW IVD test must be determined. This paper provides a statistical review of available data in an attempt to provide such a correlation. Data used include BMW and Ford IVD data on 21 different fuels from three major sources: A CRC interlaboratory study (ILS), data provided by oil and additive companies, and a set of data provided by members of the Chemical Manufacturers Association (CMA).
Considering the inherent weaknesses of the data set, the most appropriate correlation is achieved using a functional fit technique on natural logarithm transformed data. The model developed shows that, based on all the available data, a true 100 mg/valve BMW result is equivalent to a 135 mg/valve CRC Ford 2.3L result, with confidence limits ranging from 106 to 171 mg/valve. Issues relating to the correspondence of the two tests for all fuels and additives are also discussed.

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