12. Procedure
12.1 Pre-Test Procedure:
12.1.1 Engine Cooling System Flushing:
12.1.1.1 Use the following detailed procedure to flush the engine cooling system (use a flushing cart similar to the design shown in Fig.2). The circulating pump shall be capable of flowing cleanser neutralizer and water at a rate of 25 +/- 5 gal/min [95 +/- 19 L/min]. Calibrate the temperature, flow rate, and volume measuring equipment for the engine coolant flush cart at least every six months at the operating temperature of 150°F [65.6°C]).
12.1.1.2 Isolate the hoses leading from the venturi meter to the differential pressure sensor by closing the valves or removing the hoses at the venturi.
12.1.1.3 Remove the engine oil drain plug. This allows any accumulated build-up oil to drain. It also allows a way to determine the presence of any internal leaks while completing the flushing procedure.
12.1.1.4 Close the valve above the heat exchanger and isolate the coolant reservoir. This is necessary to prevent a loss of fluid during the flushing procedure and to avoid accumulation of flushing material in the coolant reservoir.
12.1.1.5 Isolate the water pump bypass by disconnecting the return hose from the intake manifold and routing it to the flush cart tank (see Fig. A3.41). Plug the water pump bypass port. (Warning - The flow rate through the intake manifold return hose should be choked down to prevent excessive flow rates through the intake manifold during flushing. This is a safety precaution and will not prevent adequate flushing of the intake manifold.)
12.1.1.6 Connect the flush cart outlet hose to the water pump inlet. Connect the flush cart inlet hose to the engine coolant outlet from the heat exchanger.
12.1.1.7 Fill the engine and flush cart with tap water (demineralized or distilled water if the tap water has a high mineral content). Circulate the water through the engine and flush cart to heat the water. Continue circulation and heating until the water temperature reaches 150 +/- 10°F (66 +/- 6°C).
12.1.1.8 Isolate the flush cart from the engine cooling system by opening the flush cart recirculation valve and closing the inlet and outlet valves.
12.1.1.9 Add the oxalic acid (see 7.7.6) at the rate of 3 oz/gal (23 g/L) of water in the flush cart system; add Petro Dispersant 425 (see 7.7.6) at the rate of 0.15 oz/gal (1 g/L). Add the cleanser directly to the flushing water.
12.1.1.10 Allow the oxalic acid to mix for 2 min in the flush cart. Open the inlet and outlet valves to the engine, and close the recirculation valve. Circulate the oxalic acid through the cooling system at a flow rate of 25 +/- 5 gal/min (1.6 +/- 0.3 L/s) for 45 min while maintaining a temperature of 150 +/- 10°F (66 +/- 6°C).
12.1.1.11 Drain the cleanser from the engine cooling system and the flush cart. Flush the system with tap water (25 +/- 5 gal/min, <100°F [95 +/- 19 L/min, <43.7°C]) until the cooling system and flush cart drains run clear.
12.1.1.12 Close the cooling system and flush cart drains. Fill the engine and flush cart with tap water and circulate the water throughout the engine until the water temperature reaches 150 +/- 10°F (66 +/- 6°C).
12.1.1.13 Isolate the flushing cart from the engine cooling system by opening the flush cart recirculation valve and closing the inlet and outlet valves.
12.1.1.14 Add the sodium carbonate at the rate of 0.05 oz/gal (3.8 g/L) of water in the flush cart system. Add the neutralizer directly to the flushing water.
12.1.1.15 Allow the neutralizer to mix for 2 min in the flush cart. Open the inlet and outlet valves to the engine and close the recirculation valve. Circulate the neutralizer through the cooling system at 25 +/- 5 gal/min (1.6 +/- 0.3 L/s) for 45 min while maintaining a temperature of 150 +/- 10°F (66 +/- 6°C).
12.1.1.16 Drain the neutralizer from the engine cooling system and the flush cart. Flush the engine cooling system and the flush cart with tap water at 25 +/- 5 gal/min (95 +/- 19 L/min) until the pH of the incoming and the outgoing water is the same. The temperature of the tap water shall be below 100°F (43.7°C).
12.1.1.17 Drain the cooling system, remove one or more freeze plugs, and inspect the coolant jacket. The cylinder walls should be clean and free of deposits when wiped. Install new freeze plugs quickly to help prevent the coolant jackets from rusting. If deposits are still present in the coolant jacket, repeat 12.1.1.6-12.1.1.17.
12.1.1.18 Disconnect the flush cart and reconnect the intake manifold coolant return line to the water pump bypass port. Reconnect the heat exchanger outlet to the water pump inlet. Charge the engine and RAC with premixed coolant (described in 8.4.1) immediately to prevent rusting of the coolant jacket.
12.1.2 Initial Test Oil Charge - Reinstall the oil pan drain plug and charge 124 +/- 1 oz (3.67 +/- 0.03 L) (fluid) of the candidate test oil to the crankcase.
12.1.3 Engine Pre-Lubrication - Rotate the oil pump clockwise until oil pressure registers in the cylinder head gallery. Turn the crankshaft a minimum of two full revolutions during the pre-lubrication procedure to ensure that the camshaft is wetted with test oil during the initial engine start-up (see 8.3.5).
12.1.4 Engine Break-In Procedure:
12.1.4.1 The laboratory ambient atmosphere shall be reasonably free of contaminants. The temperature and humidity level of the operating area are not specified. Divert air from fans or ventilation systems away from the test engine.
12.1.4.2 Prior to Step A of the break-in procedure, start the engine and adjust timing to 28° BTDC at 750 r/min.
12.1.4.3 During Step A (see Table 6 and Table 7), set the ignition-timing at 28° BTDC and allow the oil and coolant temperatures to reach 115°F (46°C). Adjust the fuel injector pulse width to provide 6.5 % CO maximum in the exhaust. Bleed the air from the engine and RAC coolant systems.
12.1.4.4 During Steps B and C (see Table 6 and Table 7), all parameters shall be controlled and recorded as normal test Stage 2 and Stage 3 conditions. Record all normal parameters in Steps B and C after operation for 35 min. In addition, record fuel pressure and RAC coolant pressure during Steps B and C.
NOTE 9 - The fuel pressure and the RAC coolant pressure are not recorded after the break-in.
12.1.4.5 At the earliest opportunity in each step, adjust the fuel injector pulse width to provide the specified values for CO and O2 in the exhaust. (Warning - Prolonged operation at a rich air-fuel ratio can cause excessive fuel dilution and alter test severity.)
NOTE 10 - The engine will normally require approximately 15 min to reach steady-state conditions after a stage change.
12.1.5 Dipstick Calibration - After the completion of Step A (see Table 6), shut the engine down (see 12.2.2). Disconnect the intake-air supply immediately after shutdown to cause the inlet air pressure to fall to atmospheric. After 20 min, calibrate the dipstick full mark at the existing sump level and set the lock nuts on the adjustable dipstick.
12.1.6 Oil Filter Removal and Filter Dummy Installation - After completion of Step C (see Table 6 and Table 7), shut the engine down (see 12.2.2). Remove the oil filter 20 min after stopping the engine. Install the oil filter dummy cap to the remote filter housing. Check and record the oil level. Do not adjust the dipstick. This oil level check is provided to establish the level of fuel dilution present after the break-in and should not be used for computing the overall test oil consumption.
12.2 Engine Operating Procedure:
12.2.1 Engine Start-up - Use the following detailed procedure each time the engine is started. (Warning - Before starting the engine, be sure there is an adequate supply of cooling water to the exhaust marine manifold. Without coolant flow, the marine manifold will overheat and sustain serious damage.)
12.2.1.1 Turn on the ignition, safety circuits, fuel management system, fuel pump, and the RAC coolant pump.
12.2.1.2 Set the fuel injector pulse width and connect the intake-air supply duct.
12.2.1.3 Crank the engine. After the engine has started, the pulse width should be returned to the Stage 3 setting at the earliest opportunity.
12.2.1.4 The fuel management, cranking, and throttle control systems should be set up to allow the engine to start within 10 s. Since spark ignition engines require a rich air-fuel ratio during startup, a Stage 1 or Stage 2 pulse width is normally necessary for hot and cold starts.
12.2.1.5 If starting difficulties are encountered, the laboratory should not continue to crank the engine excessively. Perform diagnostics to determine the reason the engine will not start (ignition problems, insufficient or excess fuel, and so forth). (Warning - Excessive cranking times can promote additional fuel dilution of the test oil and increased engine wear.) (Warning - In addition to other precautions, do not attempt to pour gasoline into the intake-air horn.)
12.2.2 Engine Shutdown:
12.2.2.1 Scheduled Shutdown Procedure - Follow the procedure detailed as follows each time a scheduled shutdown is performed. Scheduled shutdowns include shutdowns that occur during engine break-in and oil leveling:
(a) Bring the engine speed to 750 r/min.
(b) Switch the ignition off.
(c) Reduce the intake-air pressure to atmospheric.
12.2.2.2 Unscheduled Engine Shutdown - Follow the procedure detailed as follows each time an unscheduled engine shutdown is performed:
(a) Bring the engine speed to 750 r/min.
(b) Switch the ignition and RAC coolant pump off.
(c) Reduce the intake-air pressure to atmospheric.
12.2.3 Cyclic Schedule, General Description:
12.2.3.1 The test is composed of three stages as shown in Table 2. Together, the three stages comprise one cycle. Each cycle lasts 4 h and is repeated 72 times for a total of 288 h. Six consecutive cycles are completed each 24-h period. Every sixth cycle is modified to provide time for oil leveling (see A7.9).
12.2.3.2 Ramping requirements specifying parameter change rates are shown in Table 4. The rate of speed, temperature, and load changes, as well as the amount of enrichment between stages, can influence sludge and wear severity. Therefore, ramping rates are very important. Plot speed, load (torque), exhaust gas, CO, and O2 levels during Transitions 2 to 3 and 3 to 1, as shown in Fig.A7.17. Record these parameters once during test hours 12 through 48 for all tests. If a stand calibration test is conducted, also record these parameters once during test hours 240 to 288. Format and scaling shall conform to Fig.A7.17.
12.2.4 Unscheduled Downtime - The 30-min oil leveling periods are the only scheduled shutdown allowed during the test and are counted as test time. However, the test can be interrupted to perform necessary maintenance (see 12.3.6). All unscheduled downtime shall be noted in the final test report.
12.2.5 Lost Time - This is defined as time lost with respect to a master clock in an automatic control system. As an example, if the engine stalls but the master clock continues to run, the time that elapses between the engine stall and resumption under operating conditions is lost time. The test clock is restarted after the engine has reached operating conditions. Lost time shall not exceed 60 min total throughout the entire test. Make up lost time in the correct stages at some time during the test, and report it in the final test report.
12.2.6 Resumption of Test Time After Unscheduled Shutdown - After an unscheduled shutdown, test time does not begin until the engine has reached operating conditions.
12.3 Periodic Measurements and Functions:
12.3.1 Data Logging - Measure and record all data, except the specific parameters noted in this section, immediately prior to the midpoint and conclusion of Stage 1, the conclusion of Stage 2, and the conclusion of Stage 3. The format for the data logs is shown in Annex A5. Special considerations concerning computerized data acquisition are detailed in Annex A9.
12.3.2 Blowby Flow Rate Measurement - Measure and record the blowby flow rate during the second hour of Stage 1 of each cycle. The engine shall be stable at normal Stage 1 operating conditions. Measure blowby when the gas temperature is at least 90°F (32°C). Blowby gas temperature shall not differ from the laboratory average by more than +/- 10°F (5.6°C). The installation of the blowby flow rate measurement apparatus is shown in Fig. 7. The procedure for measuring blowby flow rate is detailed in 12.3.2.1. Normally, only one blowby flow rate measurement should be completed during each cycle. Additional blowby flow rate measurements are occasionally performed to determine or verify a problem with the flow rate measurement apparatus or the engine. Record additional blowby flow rate measurements and an explanation of the reason for the additional measurements. Include these data in the supplemental operational data in the final test report.
12.3.2.1 Measurement Procedure:
(a) Open the bleeder valve completely.
(b) Connect the bleeder line to the three-way valve.
(c) Connect the hose from the blowby meter surge chamber to the 0.625-in. (15.9-mm) inside-diameter air vent hose on the intake horn.
(d) Position the three-way valve to divert intake manifold vacuum from the engine PCV valve to the dummy PCV valve in the blowby measurement apparatus.
(e) Connect the apparatus pressure sensor to the dipstick tube.
(f) Adjust the bleeder valve to maintain crankcase pressure at 0.0 +/- 0.1 in. H2O (0 +/- 25 Pa).
(g) Record the differential pressure, blowby gas temperature, and the barometric pressure.
(h) Disconnect the apparatus pressure sensor and reconnect the engine crankcase pressure sensor to the dipstick tube.
(i) Disconnect the surge chamber hose from the air vent hose.
(j) Position the three-way valve to divert intake manifold vacuum to the engine PCV valve and disconnect the bleeder line from the three-way valve.
(k) Connect the air vent hose to the intake-air horn.
(l) Calculate the blowby flow rate using the calibration data for the orifice. Correct the value to standard conditions using the following equation:
where:
P = barometric pressure, in. Hg, and
T = blowby gas temperature, °F.
12.3.3 Ignition Timing Measurement - Measure and record the ignition timing at least once per two cycles in Stage 1, 2, or 3.
12.3.4 Exhaust Gas Analysis:
12.3.4.1 The recorded readings for exhaust gas CO and O2 content are taken in accordance with the instructions in 12.3.1. However, the exhaust gas CO and O2 content should be measured immediately after the engine oil and coolant temperatures have reached steady-state conditions in each stage (approximately 15 min into each stage). These data do not have to be recorded. The data are used to adjust the fuel management system to help ensure the engine is operated at the correct air-fuel ratio throughout each stage.
12.3.4.2 Measure and record the NOx content of the exhaust gas during Stage 2 once every 24 h. The intent is to take subsequent readings after 24 h of run time have elapsed.
12.3.5 PCV Valve Replacement - Replace the PCV valve at 48, 96, 144, 192, and 240 h during the oil-leveling procedure (see 12.3.6.3). Retain the used PCV valves for possible after-test clogging measurements.
12.3.6 Oil Additions and Used Oil Sampling:
12.3.6.1 The test procedure provides a forced rate of oil consumption. Make oil additions at 12-h intervals, and take used oil samples at 24-h intervals. No other new oil additions are permitted during the test. Used oil additions are permitted only during engine reassembly for maintenance (see 12.4.2.2). The new oil addition and sampling procedure is detailed as follows. The procedure is shown in a flowchart format on the Oil Sampling, Addition and Leveling Worksheet in Fig.A5.1. This form serves as the oil sampling and oil addition data sheet.
12.3.6.2 Oil Sampling Procedure:
(a) Pour 5 oz (150 mL) (fluid) of new oil in a beaker. Fifteen minutes after the engine has been switched to Stage 3, remove a 5-oz (150-mL) (fluid) purge sample into the beaker containing the new oil.
(b) Remove a 2-oz (60-mL) (fluid) analysis sample from the engine. Label the sample bottle for identification of test number, date, test hour, and oil code (see 13.7).
(c) Return the 10-oz (300-mL) (fluid) composite of new oil and purge oil to the engine at all sample hours except hour 288. Take precautions to prevent any oil loss.
(d) Do not add new oil to the engine at hour 288. This allows the final drain to be used as a backup to the 288-h sample.
12.3.6.3 Oil Leveling Procedure:
(a) After the engine is switched to Stage 3, add 5 oz (150 mL) (fluid) of new oil to the engine.
(b) Run the engine for 10 min at Stage 3 conditions.
(c) Switch the ignition off but leave the RAC coolant pump on.
(d) Bring the intake-air pressure to atmospheric.
(e) Measure and record the oil level 20 min after the engine is shut down.
(f) If the oil level is more than 12 fluid oz (360-mL) low during the first 192 h, invalidate the test because of excessive oil consumption. Use engineering judgment concerning test invalidation and termination if the oil level is more than 12 fluid oz (360-mL) low during the remainder of the test.
(g) If the oil level is above full mark, remove a sufficient quantity to bring the sump level to full.
(h) If the oil level is at or below the full mark, no leveling sample can be taken.
(i) Record all appropriate entries on the data log.
(j) Service the PCV valve in accordance with 12.3.5.
(k) Restart the engine 5 min before the scheduled beginning of Stage 1 and run the engine at Stage 3 speed and load.
(l) Resume the test at the scheduled beginning of the next cycle.
12.3.7 General Maintenance - The 30-min scheduled shutdown periods during oil leveling allow limited opportunity for engine and stand maintenance. In addition, the test can be shut down at any convenient time to perform unscheduled maintenance. However, the duration of a shutdown should be minimized. Report any unscheduled shutdown on the Special Maintenance Record. Report any attempts to restart the engine after stalling when resuming test conditions from a scheduled or unscheduled shutdown as additional start attempts on the Supplemental Operational Data Form, Fig A7.5.
12.4 Special Maintenance Procedures - Functions that require special maintenance procedures are listed in this section. These maintenance procedures are specifically detailed because of the effect on test validity or because they require special care while being completed.
12.4.1 Blowby Flow Rate Adjustment - The blowby flow rate can be adjusted if the cumulative average is projected to drift outside the specified limits. Adjust the blowby flow rate by increasing or decreasing the size of the compression ring gaps. Only two ring gap adjustments (one rering and one regap, or two regaps) may be performed during one test. Measure and record the existing ring gap dimensions before enlarging the gaps to calculate ring gap increase due to wear at the end of the test. Install a new set of torque-to-yield cylinder head bolts when reassembling the engine after the blowby flow rate adjustment. Specific limitations concerning high and low blowby flow rate adjustments are noted as follows. If stuck rings are discovered during a rework, any corrective action such as freeing the stuck ring(s) shall be noted in the Special Maintenance section of the final test report. Note whether the ring(s) are cold or hot stuck.
12.4.1.1 High Blowby Flow Rate Adjustment - An adjustment for high blowby flow rate can be performed only once and shall be completed during the first 48 h of the test. Reduce high blowby flow rate by replacing the compression rings with new rings that have smaller ring gaps.
12.4.1.2 Low Blowby Flow Rate Adjustment - Make adjustments for low blowby flow rate during the first 120 h of the test. A maximum of two adjustments for low blowby flow rate can be performed. Increase low blowby flow rate by increasing the ring gaps of the compression rings. Do not remove any deposits from the ring or ring land except those located in the ring gap.
12.4.2 Engine Disassembly and Reassembly for Maintenance (Before EOT):
12.4.2.1 When the engine is disassembled for maintenance, drain as much test oil as possible from the oil pan, and retain the oil for installation in the engine after reassembly. Take precautions to ensure the oil is not contaminated. Take precautions to ensure the deposits are not disturbed on any parts that are used to determine the final test results.
12.4.2.2 During reassembly, up to 6 oz (180 mL) (fluid) of the most recent, available oil-leveling sample may be used to lubricate the engine parts. Do not use EF-411 oil or new test oil during engine reassembly. After the engine has been reassembled, charge the oil pan with the oil removed from the oil pan during reassembly. Record all excess oil additions and report them in the Supplemental Operational Data.
12.4.3 Engine Pre-Lubrication Prior to Restart - Prelubricate the engine in accordance with 12.1.3 each time the oil charge has been removed from the engine or when the length of the shutdown exceeds 8 h.
12.4.4 Engine Parts Replacement - Parts that are rated to determine the final test results cannot be replaced during the test. The following parts can be replaced if necessary (record the circumstances involved in the replacement): engine camshaft drive belt, ignition system, PCV valve (see 12.5.5), seals and gaskets, valves or valve springs, fuel injectors, oil separator (PCV system), piston rings, and spark plugs.
12.5 Diagnostic Data Review - This section outlines significant characteristics of specific engine operating parameters. The parameters can directly influence the test or may be used to indicate normalcy of other parameters.
12.5.1 Intake Manifold Vacuum:
12.5.1.1 Intake manifold vacuum is affected by several factors, including engine load, air-fuel ratio, ignition timing, and engine wear. As a result, it is not a specifically controlled parameter but is used to monitor the condition of the engine.
12.5.1.2 The intake manifold vacuum normally decreases from Stage 1 to Stage 2, even though the engine speed, load, and lambda are the same. This is caused by the increased air temperature in the intake manifold reducing the density of the intake-air charge. The intake manifold vacuum generally increases during the first few cycles of the test, as the engine breaks-in. It may decrease toward the end of the test if the engine wears significantly. The target range offers adequate flexibility to account for differences in engine builds and barometric pressure. Operation outside of the target range suggests possible errors in load, ignition timing, exhaust gas composition, or combinations thereof.
12.5.2 Fuel Consumption Rate:
12.5.2.1 The fuel consumption rate should remain relatively constant throughout the test. Like intake manifold vacuum, fuel consumption rate is not a specifically controlled parameter but is used as a diagnostics tool. In addition, fuel consumption rate and intake manifold vacuum relate to similar operating parameters.
(a) High fuel consumption rate can promote excessive cylinder bore, camshaft, and rocker arm wear. Maintain the fuel consumption rate below 18 lb/h (8.2 kg/h) throughout the entire test.
12.5.2.2 The fuel consumption rate is normally greater in Stage 1 than in Stage 2 even though the engine speed, load, and air-fuel ratio are the same. This is caused by the increased operating temperatures in Stage 2 that allow an increase in engine efficiency and a decrease in brake specific fuel consumption (bsfc). Excessive fluctuation of the fuel consumption rate at steady-state speed and load may indicate problems with the fuel management or fuel delivery systems.
12.5.3 Spark Knock - Spark knock does not normally occur in the VE test. The octane rating of the fuel, ignition timing, engine speed and load, and operating temperatures do not promote spark knock. Spark knock indicates abnormal combustion is occurring and can cause extensive engine damage. Take corrective action immediately if spark knock is noted. Errors in the measurement and control of engine load, ignition timing, operating temperatures, and air-fuel ratio may result in spark knock.
12.5.4 Exhaust Gas Component Levels:
12.5.4.1 The CO, O2 , and NOx levels in the exhaust gas are used to determine the characteristics of combustion that occur during the test. Use these three parameters in conjunction to determine the normalcy of combustion and any significant changes in combustion that occur throughout a particular test.
12.5.4.2 Exhaust gas content measurements of CO and O2 are used to ensure the engine is being operated at a specific lambda during a specific stage. Measurements of CO and O2 are used because a specific lambda measurement has not been developed, and a numeric value for each lambda has not been determined. The lambda for each stage was chosen to produce specific effects. During Stages 1 and 2, the engine is operated at a lambda value greater than one (leaner than stoichiometric). This causes the engine to be operated at a relatively flat portion of the NOx versus O2 curve, near the point of maximum NOx. During Stage 3, the engine is operated at a lambda value less than one (richer than stoichiometric). This helps dilute the crankcase oil with fuel. The presence of components other than the component that is measured by a particular instrument can influence the accuracy of the measurement. The laboratory shall ensure the accuracy of the measurement of each specific component.
12.5.4.3 Exhaust gas CO and O2 content are useful indicators of various combustion and exhaust gas sampling problems. Content (CO) increases relatively linearly with decreasing lambda (increasing richness), for lambda values less than one (richer than stoichiometric). Content (O2) increases relatively linearly with increasing lambdas for lambda values greater than one.
12.5.4.4 High CO levels indicate excess fuel is being introduced into the engine, while low CO levels indicate too little fuel is being introduced into the engine. High or erratic CO levels can be caused by a variety of problems, including an air leak in the sampling system (The high CO results from excessive reduction of lambda to reduce the O2 level.); PCV valve that is excessively clogged; or a problem with the fuel management system.
12.5.4.5 The presence of high O2 levels and normal CO levels is usually caused by a slight misfire or a leak in the exhaust gas sampling or measurement system. The misfire can be caused by a plugged fuel injector or an ignition problem.
12.5.4.6 The VE test has been set up to produce significantly elevated exhaust gas NOx levels when compared to a production engine. This raises the NOx levels in the blowby gas and increases test severity. The NOx levels should be consistent throughout a test and relatively consistent from test-to-test. Exhaust gas NOx levels are primarily a function of combustion temperatures. As a result, the NOx levels are influenced by several factors. The cylinder head, camshaft, ignition timing, and lambda have strong effects on NOx levels. Load and engine operating temperatures have a smaller effect. Accurate NOx measurement is very sensitive to sample flow rate.
12.5.5 Crankcase Pressure - Crankcase pressure is a function of blowby flow rate and PCV valve flow. High crankcase pressure is usually caused by high blowby flow rate or a significant loss of PCV valve flow. Incorrect three-way valve plumbing or port plugging also promotes high crankcase pressure. Low or negative crankcase pressure may be caused by low blowby flow rate or a restriction of vent air to the PCV valve.
12.5.6 Oil Pressure:
12.5.6.1 The oil pressure is a function of oil viscosity and operating temperature. The oil pressure will normally be highest in Stage 1 and lowest in Stage 3. The oil pressure should remain consistent throughout the test, unless the oil exhibits a significant increase in viscosity.
12.5.6.2 An excessive oil pressure differential between the pump output and engine gallery can indicate the presence of a restriction in the external system or a large bearing clearance. An excessive oil pressure differential between the engine gallery and head gallery indicates the presence of a gallery restriction at the head gasket or an increased oil flow rate to the valve deck. When the engine gallery-to-head gallery differential pressure is lower than normal, camshaft lobe orifice plugging is indicated, causing a reduction in oil flow rate through the camshaft.
12.5.7 Oil Temperature Differential - The oil temperature differential is primarily a function of oil flow rate and oil viscosity and is normally stable throughout the test. The differential can increase if the oil viscosity increases significantly during the test.
12.5.8 Coolant Temperature Differential - The coolant temperature differential is primarily a function of the coolant flow rate and is normally stable throughout the test. Large variations in the differential can be caused by coolant flow rate or temperature measurement errors. Coolant flow rate measurement errors can be caused by foreign objects in or near the venturi flowmeter.
12.6 End of Test Procedure:
12.6.1 Engine Removal - Drain the engine and RAC coolant immediately after the completion of the last test cycle. Do not drain the engine oil. Remove the engine from the test stand and allow the engine to stand for 6 h in the same attitude in which it was positioned on the test stand. This allows the oil to drain completely into the oil pan.
12.6.2 Final Oil Drain and Engine Disassembly - Drain the oil completely and disassemble the engine. During disassembly, use extreme care to ensure the original location of the parts can be identified with respect to the cylinder number or valve location, or both.
12.6.3 Parts Layout for Rating:
12.6.3.1 Arrange the following parts in the parts rating area in accordance with the layouts detailed in this section. A photograph of the parts layout is shown in Fig.A6.12. After the parts have been arranged, allow the parts to drain a minimum of 4 h before rating. Do not attempt to accelerate or force the oil draining. Any fixtures can be used to support the parts as long as they orient the parts in the specified configurations.
12.6.3.2 RAC - Position the RAC vertically (upper jacket surface perpendicular to the ground) with the front of the RAC pointing down.
12.6.3.3 Camshaft Baffle - Position the camshaft baffle vertically (top baffle surface perpendicular to the ground) with the rear of the camshaft baffle pointing down.
12.6.3.4 Cylinder Head - Position the cylinder head with exhaust port surface pointing down. The exhaust manifold studs should be left in the head to raise the head off of the supporting surface and allow drainage.
12.6.3.5 Front Seal Housing - Position the front seal housing in the same orientation as it is installed in the engine.
12.6.3.6 Oil Pan - Position the oil pan upside down, at a 45° angle, with sump end pointing down.
12.6.3.7 Oil Screen and Pickup Tube - Position the oil screen and pickup tube in the same orientation as it is installed in the engine. The screen should be raised off of the supporting surface to allow drainage. A fixture is necessary to support the oil screen and pickup tube.
12.6.3.8 Engine Block - Position the engine block with the valve deck in a horizontal plane and facing the ceiling.