10. Basic Engine and Instrument Settings and Standard Operating Conditions
10.1 Installation of Engine Equipment and Instrumentation - Installation of the engine and instrumentation requires placement of the engine on a suitable foundation and hook-up of all utilities. Engineering and technical support for this function is required, and the user shall be responsible to comply with all local and national codes and installation requirements.
10.1.1 Proper operation of the test engine requires assembly of a number of engine components and adjustment of a series of engine variables to prescribed specifications. Some of these settings are established by component specifications, others are established at the time of engine assembly or after overhaul and still others are engine running conditions that must be observed or determined by operator adjustment, or both, during the testing process.
10.2 Conditions Based on Component Specifications:
10.2.1 Engine Speed - 900 more or less 9 rpm, when the engine is operating with combustion with a maximum variation of 9 rpm occurring during a rating. Engine speed when combustion is occurring shall not be more than 3 rpm greater than that for motoring without combustion.
10.2.2 Valve Timing - The engine uses a four-stroke cycle with two crankshaft revolutions for each complete combustion cycle. The two critical valve events are those that occur near top-dead-center (tdc); intake valve opening and exhaust valve closing. See Annex A4 for Camshaft Timing and Valve Lift Measurement Procedure.
10.2.2.1 Intake valve opening shall occur 10.0 more or less 2.5° after-top-dead-center (atdc) with closing at 34° after-bottom-dead-center (abdc) on one revolution of the crankshaft and flywheel.
10.2.2.2 Exhaust valve opening shall occur 40° before-bottom-dead-center (bbdc) on the second revolution of the crankshaft or flywheel with closing at 15.0 more or less 2.5° after-top-dead-center on the next revolution of the crankshaft or flywheel.
10.2.3 Valve Lift - Intake and exhaust cam lobe contours, while different in shape, shall have a contour rise of 6.223 to 6.350 mm (0.245 to 0.250 in.) from the base circle to the top of the lobe so that the resulting valve lift shall be 6.045 more or less 0.05 mm (0.238 more or less 0.002 in.). See Annex A4 for Camshaft Timing and Valve Lift Measurement Procedure.
10.2.4 Fuel Pump Timing - Closure of the pump plunger inlet port shall occur at a flywheel crank angle between 300 and 306°. on the engine compression stroke when the fuel flow-rate-micrometer is set to a typical operating position and the variable timing device lever is at full advance (nearest to operator). See Annex A4 for detailed instructions on setting and checking the fuel pump timing.
10.2.5 Fuel Pump Inlet Pressure - A minimum fuel head established by assembly of the fuel tanks (storage reservoirs) and flow rate measuring buret so that the discharge from them is 635 more or less 25 mm (25 more or less 1 in.) above the centerline of the fuel injection pump inlet.
10.3 Assembly Settings and Operating Conditions:
10.3.1 Direction of Engine Rotation - Clockwise rotation of the crankshaft when observed from the front of the engine.
10.3.2 Injection Timing - 13.0° before-top-dead-center (btdc), for the sample and reference fuels.
10.3.3 Injector Nozzle Opening Pressure - 10.3 more or less 0.34 MPa (1500 more or less 50 psi).
10.3.4 Injection Flow Rate - 13.0 more or less 0.2 mL/min (60 more or less 1 s per 13.0 mL).
10.3.5 Injector Coolant Passage Temperature - 38 more or less 3°C (100 more or less 5°F).
10.3.6 Valve Clearances:
10.3.6.1 Engine Stopped and Cold - Clearance between the valve stem and valve rocker half-ball set to the following approximate measurements upon assembly before the engine is operated will typically provide the controlling engine running and hot clearance:
These clearances should ensure that both valves have sufficient clearance to cause valve seating during engine warmup. The adjustable-length valve push-rods shall be set so that the valve rocker adjusting screws have adequate travel to permit the final clearance setting.
10.3.6.2 Engine Running and Hot - The clearance for both intake and exhaust valves shall be set to 0.20 more or less 0.025 mm (0.008 more or less 0.001 in.), measured under standard operating conditions with the engine running at equilibrium conditions on a typical diesel fuel oil.
10.3.7 Oil Pressure - 172 to 207 kPa (25 to 30 psi). See Annex A4 for the Adjusting Crankcase Lubricating Oil Pressure procedure.
10.3.8 Oil Temperature - 57 more or less 8°C (135 more or less 15°F).
10.3.9 Cylinder Jacket Coolant Temperature - 100 more or less 2°C (212 more or less 3°F).
10.3.10 Intake Air Temperature - 66 more or less 0.5°C (150 more or less 1°F).
10.3.11 Basic Ignition Delay - 13.0° for the sample and reference fuels.
10.3.12 Cylinder Jacket Coolant Level:
10.3.12.1 Engine Stopped and Cold - Treated water/coolant added to the cooling condenser - cylinder jacket to a level just observable in the bottom of the condenser sight glass will typically provide the controlling engine running and hot operating level.
10.3.12.2 Engine Running and Hot - Coolant level in the condenser sight glass shall be within more or less 1 cm (0.4 in.) of the LEVEL HOT mark on the coolant condenser.
10.3.13 Engine Crankcase Lubricating Oil Level:
10.3.13.1 Engine Stopped and Cold - Oil added to the crankcase so that the level is near the top of the sight glass will typically provide the controlling engine running and hot operating level.
10.3.13.2 Engine Running and Hot - Oil level shall be approximately mid-position in the crankcase oil sight glass.
10.3.14 Crankcase Internal Pressure - As mentioned by a gage or manometer connected to an opening to the inside of the crankcase through a snubber orifice to minimize pulsations, the pressure shall be less than zero (a vacuum) and typically from 25 to 150 mm (1 to 6 in.) of water less than atmospheric pressure. Vacuum shall not exceed 255 mm (10 in.) of water.
10.3.15 Exhaust Back Pressure - As measured by a gage or manometer connected to an opening in the exhaust surge tank or main exhaust stack through a snubber orifice to minimize pulsations, the static pressure should be as low as possible, but shall not create a vacuum nor exceed 254 mm (10 in.) of water differential in excess of atmospheric pressure.
10.3.16 Exhaust and Crankcase Breather System Resonance - The exhaust and crankcase breather piping systems shall have internal volumes and be of such length that gas resonance does not result. See Appendix X2 for a suitable procedure to determine if resonance exists.
10.3.17 Piston Over-Travel - Assembly of the cylinder to the crankcase shall result in the piston protruding above the top of the cylinder surface 0.381 more or less 0.025 mm (0.015 more or less 0.001 in.) when the piston is at top-dead-center. Proper positioning is accomplished through the use of plastic or paper gaskets, available in several thicknesses and selected by trial and error for assembly between the cylinder and crankcase deck.
10.3.18 Belt Tension - The belts connecting the flywheel to the absorption motor shall be tightened, after an initial break-in, so that with the engine stopped, a 2.25 kg (5 lb) weight suspended from one belt half way between the flywheel and motor pulley shall depress the belt approximately 12.5 mm (0.5 in.).
10.3.19 Setting Injector Nozzle Assembly Pressure and Spray Pattern Check - (Warning - Personnel shall avoid contact with the spray pattern from injector nozzles because of the high pressure which can penetrate the skin. Spray pattern performance checks shall be made in a hood or where adequate ventilation insures that inhalation of the vapors is avoided.)
10.3.19.1 Injector Opening or Release Pressure - The pressure adjusting screw is adjustable and shall be set to release fuel at a pressure of 10.3 more or less 0.34 MPa (1500 more or less 50 psi). Check this setting using an injector nozzle bench tester, each time the nozzle is reassembled and after cleaning. Use of a commercial injector nozzle bench tester is recommended. See Annex A4 for procedural detail.
10.3.19.2 Injector Spray Pattern - Check the spray pattern for symmetry and characteristic by inspection of the impression of a single injection made on a piece of filter paper or other slightly absorbent material placed at a distance of approximately 7.6 cm (3 in.) from the nozzle. A typical spray pattern is illustrated in Fig. 2.
10.3.20 Indexing Handwheel Reading - Handwheel readings are a simple and convenient indication of engine compression ratio which is a critical variable in the cetane method of test. The actual compression ratio is not important but an indication of compression ratio which relates to cetane number is a useful guide for selecting reference fuels to bracket the sample of diesel fuel oil. The following procedure shall be used to index the handwheel reading when the engine is new or anytime the matched handwheel assembly/cylinder head combination is interchanged or mechanically reassembled. See Appendix X3 for handwheel assembly reworking instructions.
10.3.20.1 Handwheel Micrometer Drum and Scale Setting - Refer to Table 1 to select the appropriate handwheel reading to be used in aligning the drum and scale.
10.3.20.2 Basic Setting of Variable Compression Plug - Position the variable compression plug so that the flat surface is just visible and exactly in line with the edge of the threads of the combustion pickup hole, as verified with a straightedge.
10.3.20.3 Setting Handwheel Reading - Tighten the small locking handwheel snugly by hand to ensure that the variable compression plug is held in place in the bore. Loosen the lock nut of the large handwheel and remove the locking L-shaped key. Turn the large handwheel so that the edge of the drum is in alignment with the 1.000 graduation on the horizontal scale. Reinstall the L-shaped key in the nearest keyway slot of the large handwheel with the shorter leg in the handwheel. A slight shifting of the handwheel to achieve slot line-up will not affect the indexing. Tighten the lock nut hand-tight to hold the key in place. Remove the locating screw from the drum and rotate the drum so that the zero graduation mark is in line with the selected reading from Table 1. Locate the screw hole in the drum which lines up with the handwheel hub hole and reinstall the locating screw. Wrench tighten the large handwheel lock nut and recheck that the variable compression plug is properly positioned and the handwheel reading is in accordance with the value in Table 1.
10.3.21 Basic Compression Pressure - At a handwheel reading of 1.000, the compression pressure for an engine operated at standard barometric pressure of 760 mm Hg. (29.92 in. Hg) shall be 3275 more or less 138 kPa (475 more or less 20 psi) when read as quickly as possible after shutdown of the engine which had been at standard operating conditions. If the condition is not within limits, recheck the basic handwheel setting and, if necessary, perform mechanical maintenance. See Annex A4 for the Checking Compression Pressure procedure.
10.3.21.1 For engines operated at other than standard barometric pressure, the compression pressure will typically be in proportion to the ratio of the local barometric pressure divided by standard barometric pressure. As an example, an engine located where the barometric pressure is 710 mm Hg would be expected to have a compression pressure of approximately 3060 more or less 138 kPa (444 more or less 20 psi). (Warning - In addition to other precautions, compression pressure testing using a compression pressure gage should be completed in as short a period of time as possible to avoid the possibility of combustion occurrence due to the presence of any small amount of oil in the gage or combustion chamber.)
10.3.22 Fuel Pump Lubricating Oil Level - With the engine stopped, sufficient engine crankcase lubricating oil shall be added to the pump sump so that the level is at the mark on the dip stick. (Warning - As a result of engine operation, especially when the pump barrel/plunger assembly begins to wear, the level in the sump will increase due to fuel dilution as observed through a clear plastic side plate on the pump housing. When the level rises appreciably, the sump should be drained and a fresh charge of oil added.)
10.3.23 Fuel Pump Timing Gear Box Oil Level - With the engine stopped, unplug the openings on the top and at the mid-height of either side of the gear box. Add sufficient engine crankcase lubricating oil through the top hole to cause the level to rise to the height of the side opening. Replug both openings. (Warning - The pump and timing gear box oil sumps are not connected to each other and the lubrication for the two is independent.)
10.3.24 Instrumentation - Positioning of the reference pick-ups and injector pickup is important to ensure that timing of the injection and ignition delay functions is uniform and correct.
10.3.24.1 Setting Reference Pickups - These two pickups are identical and interchangeable. They are installed in a bracket positioned over the flywheel so that they clear the flywheel indicator which triggers them.
10.3.24.2 Position each pickup in the bracket so that it is properly referenced to the flywheel indicator in accordance with the instructions supplied with the specific pickup.
10.3.24.3 Measurement of pickup to flywheel indicator clearance, if required, shall be made using a non-magnetic feeler gage.
10.3.25 Setting Injector Pickup Gap - Set the air gap to typically 1 mm (0.040 in.) with the engine stopped.
10.3.25.1 Individual pickups may require more or less air gap to obtain steady meter operation when the engine is ultimately running but too little gap can cause the ignition delay angle display to drive off scale.