ASTM D6681 Standard Test Method for Evaluation of Engine Oils in a High Speed, Single-Cylinder Diesel Engine - Caterpillar 1P Test Procedure
12. Calculation or Interpretation of Results
12.1 Test Validity Descriptions - If a test was run for 360 h according to this test method, declare the test valid.
12.1.1 If a test was not run as specified by this test method, the test is operationally invalid. Some examples of an invalid test are: use of non-specified hardware, non-specified assembly methods, a test run whose downtime is greater than 125 h, and so forth. If a test without data acquisition on any controlled parameter has a gap greater than 4 h, the test is operationally invalid.
12.1.1.1 Conduct an engineering review when a control parameter QI value is below the threshold value of zero. A typical engineering review involves investigation of the test data to determine the cause of the below threshold QI. Other affected parameters may also be included in the engineering review. This can be helpful in determining if a real control problem existed and the possible extent to which it may have impacted the test. For example, a test runs with a low QI for fuel flow. An examination of the fuel flow data may show that the fuel flow data contains several over range values. At this point, an examination of exhaust temperatures may help determine whether the instrumentation problem affected real fuel flow versus affecting only the data acquisition.
(1) For reference oil tests, conduct the engineering review jointly with the TMC. For nonreference oil tests, optional input is available from the TMC for the engineering review.
(2) Determine operational validity based upon the engineering review and summarize the decision in the comment section on the appropriate form. It may be helpful to include any supporting documentation at the end of the test report. The final decision regarding operational validity rests with the laboratory.
12.1.2 If a test completes 360 h and the piston, rings, or liner exhibit distress, consider the test non-interpretable. Likewise, if the test is terminated prior to completing 360 h for reasons including purchaser request, excessive oil consumption, or piston, ring, or liner distress, then consider the test non-interpretable.
12.2 Calculations - Use the same set of data for all calculations and graphs in the test report.
12.2.1 Quality Index - Calculate and plot the Quality Index according to the instructions in Annex A2.
12.2.2 Oil Consumption - Calculate oil consumption in grams per hour over intervals of 24 h. Delete the first 4 h of readings after an oil add from the linear regression. The linear regression technique is shown in Fig.A6.5 and Fig.A6.6. Calculate the overall average oil consumption, the initial average oil consumption, and end-of-test (EOT) average oil consumption. The initial average is the average of the data points taken at the 24th hour and 48th hour from the oil consumption graph. The EOT average is the average of the data points taken at the 336th hour and 360th hour for a full length test, or for a short-term test it is the average of the last two data points from the oil consumption graph. Calculate the natural logarithmic transformation of the average and EOT oil consumption values using the following equations:
transformed average oil consumption = ln (average oil consumption)
transformed EOT oil consumption = ln (EOT oil consumption)
12.2.3 For a period of 24 h including a shutdown, calculate the oil consumption as follows:
12.2.3.1 Do not include the first oil mass amounts removed at 4 h after a shutdown in the linear regression.
12.2.3.2 Calculate the linear regression for the period before the shutdown.
12.2.3.3 Calculate the linear regression for the period after the shutdown.
12.2.3.4 Calculate a time-weighted average from both regressions to obtain the oil consumption for that 24 h period. For example, a test experiences a 7 h shutdown at test hour 12. The slope for the first period of 8 h (hour 4 to 12) is 10.7 g/h, and the slope for the second period of 8 h (hour 16 to 24) is 2.1 g/h. The weighted average is calculated as follows:
weighted average = [(910.7 g/h)(8 h) + (2.1 g/h)( 8 h)]/(8 h + 8 h)
