ASTM D4863 Standard Test Method for Determination of Lubricity of Two-Stroke-Cycle Gasoline Engine Lubricants
8. Procedure
8.1 Assembly of Engine:
8.1.1 Initial Build - The test engine is initially built up using a new piston, rings, cylinder (modified as specified in 6.1.2), and cylinder base and head gaskets (see Annex A3). The test is not sensitive to compression ratio and this need not be determined.
8.1.2 Rebuild After Test - It is not necessary to use new parts after each test other than gaskets, a new piston, new piston rings and a new or reconditioned muffler, provided that all parts are clean and within specification with no sign of damage. The cylinder will usually require replacement after 3 to 5 complete tests (approximately 60 tightenings). After 125 to 175 complete tests (about 1000 to 1500 running hours) the entire engine will normally require replacement or a complete rebuild.
9. Operating Instructions
9.1 Fuel Temperature and Pressure - The temperature of the fuel entering the carburetor shall not exceed 25°C (77°F) and fuel delivery pressure shall be maintained at 19 to 21 mPa (2.7 to 3.0 lb/in.2).
9.2 Break-In - Each time that the cylinder is replaced the engine shall be broken in for 2 h using a 20:1 (5 % oil) by volume mixture of test gasoline and ASTM 600 reference oil under the conditions of Table 1. After break-in the piston and cylinder shall be removed and examined. If there is any sign of piston scuff, ring sticking, or other malfunction the parts involved shall be replaced and the break-in repeated. On completion of break-in and before the engine is opened for inspection, run for 5 min at 4000 r/min at no load using oil-free test gasoline.
9.3 Test:
9.3.1 All testing is performed using a 150:1 (0.67 % oil) fuel to oil volumetric mixture. The temperature of the fuel entering the carburetor shall not exceed 25°C (77°F). Run at 4000 r/min and WOT for 25 to 30 min to establish thermal equilibrium, delivering about 1.4 kW (1.9 hp). Regulate the cooling air to give a spark plug gasket temperature of 169 to 171°C (336 to 340°F). The cooling air is then shut off. As soon as the spark plug gasket temperature reaches 200°C (392°F) record the output torque, and when it reaches 350°C (662°F) record the torque again and restore the cooling air. The torque drop between 200°C (392°F) and 350°C (662°F) spark plug gasket temperature is determined. It is recommended that the torque and the corresponding spark plug gasket temperature be recorded simultaneously on a X-Y plotter and the torque drop determined from this record. After the cooling air has been restored, stabilize the plug gasket temperature again at 169 to 171°C (336 to 340°F). Run for 3 to 4 min and again shut off the cooling air to repeat the test. To obtain good repeatability it is advisable to run at an ambient temperature of about 23 to 27°C (75 to 80°F), and it is very important to protect the engine from drafts, especially during the period that the cooling air is cut off. A typical recording of torque against spark plug gasket temperature is shown as Fig. 2. Repeat to give a set of at least five tightenings. Under the conditions of 9.3.3, a set may consist of up to seven tightenings.
9.3.2 Alternate the non-reference oil and reference oil sets, running a series of two non-reference and two reference sets as indicated in Table 2. Each set shall be run without interruption, and the interval between sets shall not exceed 1 h. If the test is interrupted for any longer period the entire test shall be rerun as set-to-set comparisons are then not reliable.
9.3.3 Range of Torque Drops - For each set of tightenings, keep a running record of the range (difference between the highest and lowest values). If this exceeds 0.085 N•m (0.75 lbf•in.) run an additional tightening in case one is rejected. If, after replacing the most deviant value in the set, the range is still greater than 0.085 N•m, run one more tightening. No more than seven tightenings per set may be run. If an acceptable range cannot be obtained by discarding two out of seven tightenings terminate the test, rebuild the engine, and rerun.
9.3.4 Change-Over Engine Flush - After completing each set run the carburetor dry and change or flush out the fuel supply lines. Then restart and run for 5 min at 4000 r/min at no load on oil-free test fuel before beginning the next set.
9.3.5 Spark Plug Malfunction - Malfunctioning plugs are replaced and the test continued, repeating any set of tightenings during which this occurs (see Note 4).
9.4 Calculation - The mean (average) value and standard deviation of the torque drop are calculated separately for the reference and the non-reference oil. These values are used to determine whether there is a significant difference between the results obtained with the two oils. A sample calculation is found in Annex A4.
9.5 Anomalous Results - Check for apparent outliers, especially if the range of the results in any set of tightenings exceeds the value specified in 9.3.3. If these are suspected but are not obvious the procedures of Practice E 178 are used to test their validity. See Annex A4.
NOTE 3 - Pass-Fail Criterion - If the average torque drop obtained with a candidate oil is equal to or less than that obtained with the benchmark reference oil, as calculated by the procedures specified in Annex A4, the candidate passes.
9.6 Calibration:
9.6.1 After 30 tests or 180 days, whichever comes first, or any time a new or completely rebuilt engine is put in service, evaluate reference oils 604 and 602 oils as if they were a non-reference oil, using the 600 reference oil as the benchmark oil. For an acceptable calibration, the performance of the 602 reference oil, as determined by the procedures called for in 9.5 and 9.6, shall be rated as a pass, equal to or better than that of the 600 reference oil, and the performance of the 604 oil shall be rated as a fail.
9.6.2 In order for a test stand to be acceptable for non-reference oil evaluation it shall have been calibrated by the procedure of 9.6.1.
