SH/T 0668-1998 Lubricity Evaluation Method for Air-Cooled Two-Stroke Gasoline Engine Oils

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Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: SH/T 0668—1998 (the original first page shows "SH/T 0668—1938", which is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Chinese name: Lubricity Evaluation Method for Air-Cooled Two-Stroke Gasoline Engine Oils
• English name: Lubricity test procedure for evaluating air-cooled two-stroke gasoline engine oils
• Replacement relationship: not provided in the available source
• Adoption relationship: equivalent adoption of Japan Automobile Standards Organization JASO M340—92 (Test Procedure for Evaluating Lubricity of Two-Stroke Gasoline Engine Oils)
• Approval/implementation: approved by China Petrochemical Corporation 1998-09-24, implemented on 1999-04-01
• Responsible organization: Sinopec Research Institute of Petroleum Processing
• Drafting organizations: Tianjin Internal Combustion Engine Research Institute, Maoming Petrochemical Company Research Institute
• Main drafters: Guan Yuying, Wu Dawei, Xie Shiwen, Liang Gaosheng, Liu Chengke, Lin Yuesheng

2. Scope of application and non-applicability

• This standard specifies a test method for evaluating the lubricity of air-cooled two-stroke gasoline engine oils (abbreviated as two-stroke oils).
• Applicable to two-stroke oils used in two-stroke gasoline engines such as motorcycles, general-purpose gasoline engines, and snowmobile power units.
• Not applicable: not provided in the available source.

3. Method principle

This test uses a single-cylinder, air-cooled two-stroke gasoline engine with a displacement of 49cm³ to evaluate the lubricity of two-stroke oils. The mixing ratio of the test mixed fuel oil (standard fuel oil/two-stroke oil) is 50:1 (V/V).

The engine is operated at wide-open throttle under the condition of 4000r/min (carbon monoxide concentration adjusted to 6.0%±0.5% (V/V)). After the operating condition stabilizes, the supply of cooling air is stopped. When the spark plug gasket temperature reaches 200℃, the engine output torque value is measured; when it reaches 300℃, the torque value is measured again, and the torque decrease value is calculated.

Repeat the test 5 times to obtain a set of data. After completing one set of tests, replace the test oil and continue testing. The tests are conducted in the order of standard reference oil—sample oil—standard reference oil.

4. Reagents and materials (purity / preparation)

• Fuel oil: It is recommended to use a standard fuel oil that meets the performance requirements in Table 2. The same batch of fuel oil must be used throughout the test, because the sample oil and reference oil are to be compared relatively.
• Standard reference oil and calibration oil: The performance of the standard reference oil (JATRE-1) and calibration oils (JATRE-1 and JATRE-3) is given in Appendix A.
• Mixed fuel oil: The standard fuel oil is mixed with the standard reference oil and the sample oil separately, with a mixing ratio of 50:1. Approximately 4L of mixed fuel oil is required for each set of tests. If the two-stroke oil and the standard fuel oil separate after mixing, the test shall not be continued, and this shall be described as a special case in the report.

Table 2 Properties of standard fuel oil

Note: Other measurement items comply with SH 0041 standard.

5. Instruments and equipment

5.1 Test engine 5.1.1 The main technical parameters of the test engine are shown in Table 1.

Table 1 Main technical parameters of the engine

5.1.2 Engine modification

• 5.1.2.1 Remove the power transmission components from the crankshaft to the rear axle, so that power can be output directly from the crankshaft.
• 5.1.2.2 Remove the engine cooling fan, and supply cooling air from an external cooling system.
• 5.1.2.3 The engine air guide shroud is modified as follows, so that the cooling air after cooling the cylinder does not blow toward the carburetor (see Figure 1): a) Block the air outlet facing the side of the carburetor, so that the cooling air flows directly to the rear end. b) Remove the deflector facing the side of the carburetor, so that the cooling air flows smoothly to the rear end.

5.1.3 Oil pump: Since premixed fuel oil is used, an oil pump is not required. The inlet and outlet of the oil pump must be short-circuited, and the carburetor oil inlet must be blocked. To prevent the oil pump from seizing, the oil pump should be filled with two-stroke oil.

5.1.4 Fuel pump suction pipe: Since a fuel pump is not used, the fuel pump suction pipe installed on the crankcase must be blocked.

5.1.5 Heat shield: In order to reduce the influence of the exhaust pipe and cooling air on the intake air temperature, a heat shield is installed between the air filter and the muffler (see Figure 2). The heat shield material may be selected from aluminum, steel, or fiberglass-reinforced plastic, etc.

5.2 External cooling system: Since the engine is cooled by an external air source, a blower must be provided and connected with ducts to guide the cooling air to the required cooling locations (the blowing direction is shown in Figure 2). It is recommended to use a No. 4.5 blower driven by a 7.5kW motor.

5.3 Exhaust extraction system: Provide an axial-flow fan and connect an exhaust duct to the engine muffler to discharge the engine exhaust gas directly outdoors. It is recommended to use a No. 4 axial-flow fan driven by a 0.6kW explosion-proof motor.

5.4 Dynamometer: The selected dynamometer should be able to absorb power 2.0kW at 4000r/min. The dynamometer is preferably connected directly to the engine crankshaft, or it may be connected through a reduction device, but power losses must be compensated. Since the engine's starter motor is not used, the dynamometer preferably has the function of being able to back-drive the engine, or a starter motor should be provided.

5.5 Measurement and control equipment: The measurement and control equipment should meet the requirements of the test conditions in Table 3 and Table 4 and the measurement requirements specified in Table 5.

• 5.5.1 Torque measuring instrument: range 0~10N·m, measurement accuracy ±0.01N·m.
• 5.5.2 Tachometer: measurement accuracy ±10r/min.
• 5.5.3 Thermometer: measurement accuracy 1℃.
• 5.5.4 Recorder: A recorder capable of continuous measurement and data recording should be selected. If this cannot be achieved, recording may be made once every 15s or once every 10℃.
• 5.5.5 Fuel flow meter: The measurement range should satisfy 0~3.0L/h.
• 5.5.6 Carbon monoxide concentration measuring instrument: range 0~10% (V/V), measurement accuracy 0.1% (V/V).
• 5.5.7 Dry and wet bulb thermometer: measurement accuracy 0.1℃.
• 5.5.8 Barometer: measurement accuracy ±0.1kPa.

5.6 Measurement positions for temperature and carbon monoxide concentration

• 5.6.1 Spark plug gasket temperature: The spark plug gasket temperature is measured to control and monitor the engine thermal load state during the test. Examples of the measurement position and thermocouple are shown in Figure 3 and Figure 4.
• 5.6.2 Intake air temperature: The measurement position for the air temperature at the air filter inlet is shown in Figure 5.
• 5.6.3 Carbon monoxide concentration in exhaust: The measurement position is shown in Figure 6.

5.7 Fuel oil supply system: Since the fuel oil supply relies on gravity head pressure, a container capable of holding at least 4L of fuel oil must be prepared and placed at a position 500mm higher than the carburetor float chamber. The oil pipe structure should minimize the fuel oil head pressure loss, and there must be no air bubbles in the pipeline.

6. Recommended operating conditions

• Engine speed: 4000±20 r/min
• Throttle opening: 100%
• Carbon monoxide concentration: 6.0±0.5% (V/V)
• Fuel consumption: 1.5±0.5 L/h
• Mixing ratio (standard fuel oil/two-stroke oil): 50:1 (V/V)
• Spark plug gasket temperature: maintained at 160℃±5℃ during pre-operation; measurement points 200℃ and 300℃
• Break-in conditions are shown in Table 3.

Table 3 Break-in conditions

Table 4 Engine operating conditions

7. Sampling and sample preparation

• 7.1 Engine preparation
  • 7.1.1 For a new engine or after repair and maintenance, before formal testing, it must be run in according to the provisions of Table 3. During the run-in operation of stage 1, adjust the cooling air so that the spark plug gasket temperature reaches 165℃±5℃ (original text "165° 5C", requires confirmation against the source standard (source-text extraction)), and the carbon monoxide concentration in the exhaust should reach 6.0%±0.5% (V/V). If it exceeds this range, it can be adjusted by adjusting the carburetor main nozzle and the clip position of the needle (the recommended main nozzle number is 75A, and the needle clip position is the third groove from the top). The run-in uses a mixed fuel oil blended with standard reference oil, and its mixing ratio (standard fuel oil/two-stroke oil) is 50:1 (V/V).
  • 7.1.2 Engine assembly: After cleaning the engine parts, they should be assembled according to the engine repair manual provided by the manufacturer, and a small amount of standard reference oil should be applied to the surfaces of the parts.
  • 7.1.3 Replacement criteria for parts: Parts should be replaced under the following conditions: a) 20 sets of tests have been conducted; b) The initial torque when using standard reference oil (at spark plug gasket temperature 200℃) decreases by more than 10%; c) During disassembly and inspection, there are leakage marks on the piston skirt or scratches on the piston and cylinder that affect the test.
• 7.2 Preparation of mixed fuel oil: Standard fuel oil is mixed with standard reference oil and sample oil respectively, with a mixing ratio of 50:1. Each set of tests requires approximately 4L of mixed fuel oil to be prepared. If the two-stroke oil and standard fuel oil separate after mixing, the test shall not proceed and shall be described as a special case in the report.
• 7.3 Preparation of the fuel supply system: Each time the sample oil is changed, the fuel oil in the fuel tank, fuel line, and carburetor float chamber should be drained, and after rinsing with standard fuel oil, the next mixed fuel oil should be filled into the fuel tank, then loosen the drain screw of the float chamber and release about 10mL of mixed fuel oil to eliminate the influence of the previous set of tests.

8. Analysis procedure

8.1 The engine is operated according to the following steps

• 8.1.1 Operate the engine according to the conditions in Table 4 for 30min. During this period, adjust the cooling air so that the spark plug gasket temperature is maintained at 160℃±5℃.
• 8.1.2 Stop supplying cooling air, and continuously record the spark plug gasket temperature and torque values. If continuous recording is not possible, record once every 15s or at intervals of 10℃.
• 8.1.3 The torque values at spark plug gasket temperatures 200℃ and 300℃ must be specially recorded, and once recording is completed, immediately supply cooling air.
• 8.1.4 After supplying cooling air for about 10min, and after confirming that the spark plug gasket temperature has dropped to 160℃±5℃, stop supplying cooling air. See Appendix B for the test run mode.
• 8.1.5 Repeat steps 8.2~8.4 5 times as one set of tests, and obtain one set of data. If any one of the recorded 5 torque drops exceeds ±0.028N·m of the average value of this set of data, discard this value as an abnormal value, continue to repeat the test once, and recalculate the average value of this set of data. When any one of the 5 values still exceeds 0.028N·m of the new average value, the test can be repeated once more. However, the test for each oil shall not exceed 7 times, otherwise the test shall be terminated.
• 8.1.6 If the test has been repeated 7 times, and any 5 values are not within the range of 0.028N·m of their average value, the test is invalid; identify the cause and adjust the engine, then retest (all data previously obtained before this set of tests on the same day should be discarded, because this test is considered unreliable).
• 8.1.7 The test is completed within the same day in the order of standard reference oil—sample oil—standard reference oil, to reduce the influence of the environment on the test results. During the test, measure and record the items specified in Table 5.

Table 5

8.2 Data processing: Statistically process the measured data to relatively compare the lubricity of the sample oil. If there is a statistically significant difference between the two sets of standard reference oil test data, the test is considered unreliable.

8.3 Calculation of corrected torque: Convert the measured torque values to corrected torque values under standard intake conditions according to the method of GB/T 5363, and then calculate the torque reduction value.

8.4 Judgment of test reliability: At a confidence level of 95%, if there is no statistically significant difference between the torque drops of the two standard reference oils, the test is considered reliable. If there is a significant difference, the test is unreliable.

9. Qualitative and quantitative and calculation formulas

9 Result analysis (example of statistical analysis process): Take the data in Table 6 as an example for statistical analysis.

Table 6 Corrected torque drop data

According to the provisions of 8.1.5, through analysis, the value in parentheses in Table 6 (0.290) is not within the range of ±0.028N·m and should be discarded.

9.1 Calculation of average torque drop, standard deviation, and variance The average torque drop X, standard deviation σ, and variance are calculated according to formula (1), formula (2), and formula (3), respectively:

(1) X = ΣXᵢ / n (2) σ = √[Σ(Xᵢ−X)² / (n−1)] (3) Variance = σ²

Where: Xᵢ——each torque reduction value; n—— number of data; ΣXᵢ——sum of each torque reduction value.

9.2 List the above statistical results in Table 7

Table 7 Calculation results of average, standard deviation, and variance

9.3 Test reliability check The prerequisite for test reliability is: there is no significant difference between the test results of the two standard reference oils. The following is an explanation of reliability.

9.3.1 The combined standard deviation (σwe) between the two standard reference oil test results and the t test value (t) are calculated according to formula (4) and formula (5), respectively:

(4) σwe = √{[(nₐ−1)σₐ² + (n_c−1)σ_c²] / (nₐ+n_c−2)} (5) t = |Xₐ−X_c| / [σwe√(1/nₐ+1/n_c)]

Substituting the results of Table 6 into formula (4) and formula (5) gives: σwe = 0.006907, t = 1.3736

9.3.2 Compare the obtained t- test value (t) with the t- critical value (tcrit) in Appendix C. If at a confidence level of 95%, t ≤ tcrit, then it is considered that there is no significant difference between the first and second tests of the standard reference oil. Here the degrees of freedom φ are (n−1), but when the sample oil is two combinations, φ is (nₐ+n_c−2). Therefore, the degrees of freedom for the standard reference oil are 8. From Appendix C, tcrit = 1.860 is found.

Test result: t [1.3736] < tcrit [1.860], it can be considered that there is no significant difference between them, and the test is reliable.

9.4 The significant difference test between the standard reference oil and the sample oil is similar to the significant difference test between the two standard reference oils, where the degrees of freedom are (nₐ+n_b−2).

9.4.1 The combined standard deviation (σwd) between the standard reference oil and the sample oil and the t test (t) can be obtained from formula (4) and formula (5): σwd = 0.007226, t = 5.1543

9.4.2 From Appendix C, tcrit = 1.771 is found (confidence level 95%, degrees of freedom 13), test result t > tcrit, it can be considered that there is a significant difference between them, indicating that the lubricity of the sample oil is worse than that of the standard reference oil.

9.5 The lubricity index (LIX) is calculated according to formula (6):

(6) LIX = X_d / X_b

Where: X_d—— average corrected torque drop of the standard reference oil (sum of two runs); X_b—— average corrected torque drop of the sample oil.

9.6 initial torque index (TIX) is calculated according to formula (7):

(7) TIX = average corrected torque of the sample oil at 200℃ / average corrected torque of the standard reference oil at 200℃ × 100

10. Precision

• Determination of an outlier in a single torque drop: if any one of the recorded 5 torque drops exceeds ±0.028N·m of the average of this set of data, it is regarded as an outlier and discarded.
• The test for each oil shall not exceed 7 times; otherwise, the test is terminated.
• Judgment of test reliability: at the 95% confidence level, if there is no statistically significant difference between the torque drops of the two standard reference oils, the test is considered reliable.
• Other precision indicators: not provided in the available source.

11. Report

Fill the test results into Table 8.

Table 8 Air-cooled two-stroke oil lubricity test results table

12. Normative references

The provisions of the following standards, through reference, constitute a part of this standard. Unless otherwise expressly specified in the standard, the following referenced standards shall all be currently effective standards.

Editor's note: The standard numbers and standard names of the referenced standards in this standard have changed as follows:

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick-reference Q&A