ASTM D6891 Standard Test Method for Evaluation of Automotive Engine Oils in the Sequence IVA Spark-Ignition Engine
10. Data Acquisition, Reference Oil Application, and Equipment Calibration and Maintenance
10.1 Data Acquisition:
10.1.1 Computer Data Acquisition - The test stand log operational data using a computer data acquisition system with sensor configurations process is described in 10.1.2 - 10.1.4.

10.1.2 Frequency of Logged Steady-State Data - Log the Stage I steady-state (last 45 min of stage) operational conditions every 2 min or more frequently. Log the Stage II steady-state (last 5 min of stage) operational conditions every 30 s or more frequently.

10.1.3 Frequency of Logged Transient Data - Define the transient time as the first 5 min following operational stage changes. Computer log and plot the cycle 5 transient data. Log the critical parameters (engine speed, torque, cylinder head oil gallery temperature, coolant out temperature) once per second or higher frequency. If cycle 5 transients are beyond the procedural limits defined in 11.2.6, document and confirm corrective action with the next available transition plot.

10.1.4 Signal Conditioning - Do not exceed the controlled operational parameters for system time response as shown in Table 2. The system time response includes the total system of sensor, transducer, analog signal attenuation, and computer digital filtering. Use single-pole type filters for attenuation. For temperature sensors, grounded thermocouples are preferred, although ungrounded thermocouples are acceptable.
10.1.4.1 Isolated Inputs - If using grounded and sheathed thermocouples, use signal-conditioning modules to provide isolated inputs to the digital computer.

10.2 Reference Oil Application:
NOTE 9 - 10.2.6 and 10.2.7 and Annex A1 - Annex A4 describe the involvement of the TMC in respect to calibration procedures and acceptance criteria for a testing laboratory and a test stand, and the issuance of Information Letters and memoranda affecting the test method.
10.2.1 Testing of Reference Oils - Periodically conduct tests on reference oils according to the following:
10.2.1.1 Conduct reference oil tests on each calibrated test stand within a laboratory according to TMC guidelines.

10.2.1.2 Obtain reference oils directly from the TMC. These oils are formulated or selected to represent specific chemical types or performance levels, or both. They are usually supplied directly to a testing laboratory under code numbers to ensure that the laboratory is not influenced by prior knowledge of acceptable results in assessing the test results. The TMC determines which specific reference oil the laboratory shall test.

10.2.1.3 Unless specifically authorized by the TMC, do not analyze reference oils, either physically or chemically. Identification of reference oils by such analyses could undermine the confidentiality required to operate an effective reference oil system. Therefore, reference oils are supplied with the explicit understanding that they will not be subjected to analyses other than those specified in this procedure, unless specifically authorized by the TMC. If so authorized, prepare a written statement of the circumstances involved, the name of the person authorizing the analysis, and the data obtained; furnish copies of this statement to the TMC.

10.2.2 Reference Oil Test Frequency - Conduct reference oil tests according to the following frequency requirements:
10.2.2.1 For a given, calibrated test stand, conduct an acceptable reference oil test after no more than 15 test starts have been conducted, or after six months have elapsed, whichever occurs first.

10.2.2.2 After starting a laboratory reference oil test, non-reference oil tests may be started on any other calibrated test stand.

10.2.2.3 Reference oil test frequency may be adjusted due to the following reasons:

10.2.3 Procedural Deviations - On occasions when a laboratory becomes aware of a significant deviation from the test method, such as might arise during an in-house review or a TMC inspection, the laboratory and the TMC shall agree on an appropriate course of action to remedy the deviation. This action may include the shortening of existing reference oil calibration periods.

10.2.4 Parts and Fuel Shortages - Under special circumstances, such as industry-wide parts or fuel shortages, the surveillance panel may direct the TMC to extend the time intervals between reference oil tests. These extensions shall not exceed one regular calibration period.

10.2.5 Reference Oil Test Data Flow - To ensure continuous severity and precision monitoring, calibration tests are conducted periodically throughout the year. There may be occasions when laboratories conduct a large portion of calibration tests in a short period of time. This could result in an unacceptably large time frame when very few calibration tests are conducted. The TMC can shorten or extend calibration periods as needed to provide a consistent flow of reference oil test data. Adjustments to calibration periods are made such that laboratories incur no net loss (or gain) in calibration status.

10.2.6 Special Use of the Reference Oil Calibration System - The surveillance panel has the option to use the reference oil system to evaluate changes that have potential impact on test severity and precision. This option is only taken when a program of donated tests is not feasible. The surveillance panel and the TMC shall develop a detailed plan for the test program. This plan requires all reference oil tests in the program to be completed as close to the same time as possible, so that no laboratory/stand calibration is left in an excessively long pending status. In order to maintain the integrity of the reference oil monitoring system, each reference oil test is conducted so as to be interpretable for stand calibration. To facilitate the required test scheduling, the surveillance panel may direct the TMC to lengthen and shorten reference oil calibration periods within laboratories such that the laboratories incur no net loss (or gain) in calibration status.

10.2.7 Donated Reference Oil Test Programs - The Surveillance Panel is charged with maintaining effective reference oil test severity and precision monitoring. During times of new parts introductions, new or re-blended reference oil additions, and procedural revisions, it may be necessary to evaluate the possible effects on severity and precision levels. The surveillance panel may choose to conduct a program of donated reference oil tests in those laboratories participating in the monitoring system, in order to quantify the effect of a particular change on severity and precision. Typically, the surveillance panel requests its panel members to volunteer enough reference oil test results to create a robust data set. Broad laboratory participation is needed to provide a representative sampling of the industry. To ensure the quality of the data obtained, donated tests are conducted on calibrated test stands. The surveillance panel shall arrange an appropriate number of donated tests and ensure completion of the test program in a timely manner.

10.2.8 Reporting of Reference Oil Test Results - Report the results of all reference oil tests to the TMC according to the following directives:
10.2.8.1 Transmit results to the TMC within five days of test completion by way of electronic data transfer protocol as outlined in the Data Communication Committee, Electronic Test Report Transmission Model (ETRTM). The ETRTM can be obtained from the TMC.

10.2.8.2 If the test was conducted during a time extension permitted by the TMC, so indicate in the Comments section of the test report.

10.2.8.3 For an acceptable reference oil test, conducted following an unacceptable reference oil test, provide sufficient information in the Comments section of the test report to indicate how the problem was identified and corrected, insofar as possible, and how it was related to non-reference oil tests conducted during the period of time that the problem was being solved.

10.2.9 Evaluation of Reference Oil Test Results - The TMC evaluates the reference-oil test results for both operational validity and statistical acceptability. The TMC may consult with the test laboratory in case of difficulty, as follows:
10.2.9.1 Immediately upon receipt of the reference-oil test results from the test laboratory, the TMC evaluates the laboratories decision on operational validity. For operationally valid tests, the TMC then evaluates the pass/fail parameters according to the Sequence IVA Lubricant Test Monitoring System (TMC Memorandum 94-200). If the test is judged acceptable, the reference oil code is disclosed by the TMC to the test laboratory. The TMC conveys to the test laboratory its preliminary findings based on the limited information available to them.

10.2.9.2 Subsequently, upon receipt of the information detailed in 11.4.4, the TMC reviews all reference-oil test results and reports to determine final test acceptability.

10.2.9.3 In the event the reference oil test is unacceptable, the test laboratory shall provide an explanation of the problem relating to the failure. If the problem is not obvious, all test-related equipment shall be re-checked. Following this re-check, the TMC assigns another reference oil for testing by the laboratory.

10.2.9.4 The TMC decides, with consultation as needed with industry experts (testing laboratories, members of the ASTM Technical Guidance Committee and of the Surveillance Panel, and so forth), whether the reason for any failure of a reference oil test is a false alarm, testing stand, testing laboratory, or industry-related problem. The Sequence IVA Surveillance Panel shall adjudicate all industry problems.

10.2.10 Status of Non-Reference Oil Tests Relative to Reference Oil Tests - Non-reference oil tests may proceed within a given laboratory during reference oil testing based upon the following:
10.2.10.1 During the time of conducting a reference oil test on one test stand, non-reference oil tests may be conducted on other previously calibrated stands. If the reference oil test is acceptable to the TMC, the non-reference oil tests shall be considered to have been run in a satisfactorily calibrated laboratory.

10.2.10.2 If a reference oil test is unacceptable, and it is determined that the problem is isolated to an individual test stand, consider other test stands to remain calibrated, and testing of non-reference oils may proceed on those other stands.

10.2.10.3 If a reference oil test is unacceptable, and it is determined that the problem is laboratory related, non-reference tests running during the problem period shall be considered invalid unless there is specific evidence to the contrary for each test.

10.2.11 Status of Test Stands Used for Non-Standard Tests - If a non-standard test is conducted on a previously calibrated test stand, conduct a reference oil test on that stand to demonstrate that it continues to be calibrated, prior to running standard tests.

10.3 Equipment Calibration:
10.3.1 Instrumentation Calibration - Perform a thorough recalibration adjustment of all instrumentation and transducers, including computer channels, according to the requirements that follow. Perform additional calibration checks whenever operational data indicates an abnormality. Standards used for instrumentation calibration shall be traceable to that country's specific national standards organization. The accuracy of the standard shall be a minimum of four times better than the accuracy of the test stand instrumentation.

10.3.2 Dynamometer Torque Measurement - Scale the final readout of engine torque (N·m). Calibrate the force measurement and readout system with deadweights. Coolant flow through the dynamometer, reaction forces due to coolant plumbing, and brinnelled trunnion bearings of the dynamometer may affect calibration by temperature excursions of the dynamometer electronic force transducer. The torque measurement accuracy shall be +/- 0.2 N·m. Perform this calibration prior to every test start.

10.3.3 Coolant Flow Measurement Systems - Check the venturi flow meter for calibration using a 50 % water/glycol fluid controlled at 50 °C. Calibrate the flow meter as installed in the system at the test stand. Alternatively, the flowmeters may be detached from the test stand and calibrated, providing the adjacent upstream and downstream plumbing remain intact during the calibration process. Calibrate the flow meters with a turbine flow meter or by a total volume per unit time method. The coolant flow measurement accuracy shall be +/- 0.3 L/min. Calibrate the coolant flow measurement system every 6 months.

10.3.4 Fuel Consumption Measurement Calibration - Check the mass flow meter or gravimetric systems for calibration every 6 months. The fuel flow measurement accuracy shall be +/- 0.05 kg/h.

10.3.5 Air-to-Fuel Sensor Calibration - Recalibrate the AFR meter per the instrument manufacturer's recommended procedure when the universal (or wide-range) exhaust gas oxygen sensor is replaced.

10.3.6 Temperature Measurement Calibration - Calibrate the temperature measurement every 6 months. The temperature measurement system accuracy shall be within +/- 0.5 °C of the laboratory calibration standard. The calibration standard shall be traceable to national standards.
10.3.6.1 Recalibration of the Oil Cylinder Head Temperature thermocouple after each cylinder head change is recommended.

10.3.7 Pressure Measurement Calibration - Check the pressure measurement systems for calibration every 6 months. The exhaust pressure measurement accuracy shall be +/- 1.0 kPa.

10.3.8 Humidity of Induction Air Calibration:
10.3.8.1 Calibrate the primary laboratory measurement system at each test stand every 6 months using a hygrometer with a minimum dew point accuracy of +/- 0.55 °C at 16 °C. Locate the sample tap on the air supply line to the engine, between the main duct and 1000 mm upstream of the intake air cleaner. The calibration consists of a series of paired humidity measurements comparing the laboratory system with the calibration hygrometer. The comparison period lasts from 20 min to 2 h with measurements taken at intervals of 1 min to 6 min, for a total of 20 paired measurements. The measurement interval shall be appropriate for the time constant of the humidity measurement instruments.

10.3.8.2 Verify that the flow rate is within the equipment manufacturer's specification and that the sample lines are non-hygroscopic. Correct dew point hygrometer measurements to standard conditions (101.12 kPa) using the appropriate equation. Compute the difference between each pair of readings and calculate the mean and standard deviation of the twenty-paired readings. The absolute value of the mean difference shall not exceed 1.43 g/kg, and the standard deviation shall not be greater than 0.714 g/kg. If these conditions are not met, investigate the cause, make repairs, and recalibrate. Maintain calibration records for 2 years.

10.3.9 Cam Lobe Profilometer Calibration - Follow the manufacturer's instruction for calibration and verification checks of the profilometer. Calibrate the profilometer at least annually.

10.3.10 Head Fixture Calibration - Calibrate the head fixture at least once every 3 months. The testing laboratory shall determine the calibration technique.

10.4 Equipment Maintenance:
10.4.1 Blowby Flow Rate Measurement System Maintenance - Clean the blowby measurement apparatus at least weekly. Exercise particular care when cleaning the orifice meter assembly. Clean the 3-way valve by soaking the valve in solvent (see 6.1.3). Inspect the port passages and remove any carbonaceous deposits by scraping. When disassembling the valve for cleaning, properly seat the core upon reassembly.

NOTE 10 - Internal leakage within the 3-way valve may cause some of the blowby gas to pass directly to the intake manifold from the test PCV valve and result in erroneous blowby flow rate measurements.

10.4.2 Periodic Cleaning of Coolant System Plumbing - Internally clean the engine coolant system plumbing each time a new engine is installed by a chemical flushing method. Use any commercial radiator cleaner/flush chemical that is safe for vehicle use. After using the cleaner, flush the test stand coolant plumbing with fresh water, until clear. If using a flush cart, stronger chemicals may be used providing the engine coolant pumps are bypassed and the instrument transducers are not included in the flush (see 6.1.3).

10.4.3 Oil Cooler Replacement - Replace the oil cooler (see Annex A6) when replacing the short-block assembly.