AIR INTAKE AND EXHAUST SYSTEMS

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TURBOCHARGER

DESCRIPTION
The turbocharger assembly, Fig. 8-I, is primarily used to increase engine horsepower and provide bet-ter fuel economy through the utilization of exhaust gases. As shown in cross-section, the turbocharger has a single stage turbine with a connecting gear train. The connecting gear train is necessary for en-gine starting, light load operation, and rapid accel-eration. Under these conditions there is insufficient exhaust heat energy to drive the turbine fast enough to supply the necessary air for combustion, and the engine is actually driving the turbocharger through the gear train assisted by exhaust gas energy. When the engine approaches full load, the heat energy in the exhaust, which reaches temperatures approaching 1000° F., is sufficient to drive the turbocharger with-out any help from the engine. At this point, an over-running clutch in the drive train disengages and the turbocharger drive is mechanically disconnected from the engine gear train.
The turbine shaft is driven by the engine gear train through a series of gears in the turbocharger. A tur-bocharger drive gear, which is a part of the spring drive gear assembly, meshes with the turbocharger idler gear, driving the carrier drive gear. The carrier shaft drives the sun gear on the turbine shaft through three planet gears when the turbocharger is being driven by the engine. The sun gear meshes with the planet gears which, in turn, mesh with a ring gear in the overrunning clutch assembly. The ring gear is fixed, when the engine is driving the turbine, because the direction of torque at the ring gear locks the over-running clutch. When the turbine is being driven en-tirely by exhaust gas energy, the direction of torque is reversed and the clutch overruns, allowing the ring gear to rotate.
The overrunning clutch consists of 12 rollers in ta-pered slots. The slots are formed by the combination of a stationary clutch support and the pockets in the cam plate. The cam plate, ring gear support, and the ring gear are dowelled and bolted together, and rotate as a unit. When the engine is driving the turbine, the rollers are wedged in the small side of the cam plate pockets, as a result of the direction of torque, locking the cam plate to the sta-tionary clutch support. This locking action prevents the ring gear from turning. Because the planet gear shafts are driven as a part of the carrier shaft, the planet gears rotate in the locked ring gear to drive the sun gear on the turbine shaft. When the exhaust energy becomes great enough to drive the turbine without help from the engine, the torque at the sun gear, planet gears, and ring gear reverses direction. This causes the rollers to move to the wide end of the cam plate pocket, unlocking the clutch, permitting it to overrun, and allowing the ring gear to rotate. From this point on, with increased load and speed, the turbocharger overruns the engine drive and the planet gears slowly turn the ring gear.

TURBOCHARGER REMOVAL

1. Remove roof hatch.

2. Disconnect and remove the water lines to and from the aftercooler assemblies.

3. It is advisable to remove the aftercoolers from the ducts rather than to remove them as an assembly, because of the weight involved.

4. Remove the oil line clamp from the right after-cooler duct.

5. Remove both aftercooler duct assemblies. 6. Re-move the auxiliary drive assembly.

7. Remove the oil separator assembly.

8. Remove the expansion joint between the turbo-charger and the engine exhaust manifold.

9. Disconnect the exhaust elbow from the top of the turbine exhaust duct. Remove the elbow.

10. Remove air duct assembly from turbocharger air inlet assembly and remove air inlet.

11. Connect lifting chains to eyes screwed into the four tapped bosses on the turbocharger. Maintain even tension on all four chains so that turbo-charger will hang properly. If a hand-operated chain hoist is available, it should be used between the chain device and the main lifting crane to simplify vertical positioning and tension adjust-ment during turbocharger removal. Do not allow chains to drag against the exhaust duct.

12. Remove bolts attaching turbocharger housing to camshaft gear train housing. The turbocharger is now held in position by the No. 2 idler gear stub-shaft and lifting device.

CAUTION: Before removing the turbocharger, be sure to remove (if applied) two studhead bolts which hold the aftercooler piping bracket to the turbocharger.

13. Using jackscrews between the turbocharger hous-ing and the gear train housing, jack the turbo-charger away from the engine until the turbo-charger clears the No. 2 stubshaft.

NOTE: Care should be exercised, when removing turbocharger, that No. 2 idler gear is not dis-engaged from camshaft drive gear, as engine timing will have to be checked if gear is dis-engaged.

14. Using a 1-ton crane, lift the turbocharger clear of the engine and place it in shipping container for transportation.

AIR BOX INSPECTION

1. Clean the air box to remove all evidence of alu-minum dust and chromate or borate water stains.

2. Inspect the cylinder assemblies for broken valves, valve blow, cracked pistons, broken piston rings, scored pistons and liners.

3. Determine the cause of the turbocharger failure and correct any conditions that might have ag-gravated the failure.

4. Clean all gasket surfaces on the engine, the tur-bocharger to be applied, and the air ducts.

TURBOCHARGER

GEAR TRAIN INSPECTION

1. Visually check the gear train for nicks, burrs, evidence of improper backlash, and uneven or excessive wear. Make any necessary corrections.

2. Clean the No. 2 idler turbocharger locating stub-shaft, using an oil stone. Remove all indications of fretting. Inspect the seal groove for nicks and burrs, and smooth the surface after removal of any nicks or burrs.

3. Check the gear train area and remove any metal-lic debris that might be found.

EXHAUST MANIFOLD INSPECTION

1. Inspect the exhaust manifold for foreign material, and completely remove any found. The manifold should be removed, if in doubt, to look for cracked leg baffles which should be removed, and cracked expansion joints, which should be replaced.

2. Inspect the condition of the exhaust manifold leg gaskets and the torque on the bolts, which should be 176 N-m (130 ft-lbs). Also, check the mani-fold connector fasteners which should be 108 N-m (80 ft-lbs). Check the condition of the adapter to turbocharger bellows connections, and other locations where possible leaks might occur in the exhaust system.

3. Inspect the adapter assembly between rear expan-sion joint and chamber assembly for condition of screen. If foreign material is present in the ex-haust manifold, it is recommended that the screen be magnaflux inspected.

CAUTION: Inspect the exhaust silencer (if applicable) for foreign material and remove any which may be found.

LUBRICATING OIL SYSTEM

1. Remove the disposable turbocharger oil filter and the soak back oil filter elements. Install new ele-ments and check that the filter bowls are full of clean lubricating oil, and that the springs and gaskets are in place.

2. If required, drain and completely clean the sys-tem.

a. If the oil system is contaminated with debris, flush the system and install new filter ele-ments.

b. Install new main oil filter elements, and clean and check the main oil filter relief valves.

c. Recharge the oil system after the replacement turbocharger is applied and the oil system and all filters have been conditioned to re-ceive the new clean oil.

d. Check the soak back pump function and op-eration. Check the pump bypass relief valve for proper operation.

TURBOCHARGER INSTALLATION

1. Apply the lifting device to the turbocharger as described in the turbocharger removal procedure. (The turbocharger shipping container, plus the masking of all openings on the turbocharger is the best protection and insurance against damage, rust, and contamination that can be given the tur-bocharger prior to installation.)

2. To determine the impeller eye clearance, remove the air inlet assembly before removing the turbo-charger from the container pedestal. Chalk mark an impeller blade at the 12 o'clock position so that the impeller can be returned to this position when the eye clearance is rechecked after turbo-charger installation. Two sets of feeler gauges should be used when making this check. Clear-ances should be determined with a heavy drag on the feelers. Perform check as follows:

a. Insert approximately the same feeler gauge thicknesses at the ends of the impeller blades at the 3 and 9 o'clock positions simultane-ously to determine the available horizontal clearance. Record the clearances.

b. A feeler gauge should be used at the 12 o'clock position to determine the upper verti-cal clearance. Leaving the feeler gauge in po-sition at the 12 o'clock position, use another

feeler to determine clearance at the 6 o'clock position. Record the clearances obtained

3. Apply a thin coat of gasket compound to the camshaft drive housing and apply a new gas-ket to the housing.

4. Apply a new "O" ring seal to the engine No. 2 idler stubshaft.

5. Apply some clean lubricating oil to the No. 2 idler stubshaft and to the turbocharger drive gear.

6. Lift the turbocharger and remove covering from all openings, except the exhaust stack and exhaust inlet duct.

7. Align the turbocharger, guiding it onto the No. 2 idler stubshaft and into position. Care must be taken to ensure proper mesh of the turbo-charger idler gear and the turbocharger drive gear on the engine.

8. Use hardened washers and damper springs with the 3/4" bolts, and apply all the turbo-charger to camshaft drive housing bolts before removing the lifting device. Snug up bolts, but do not tighten.

9. Install the auxiliary drive assembly on the tur-bocharger and check the gear backlash be-tween the camshaft drive gear and the auxil-iary drive gear.

Check the backlash with a dial indicator, Fig. 8-2. Attach a small "C" clamp to the coupling flange so that clamp contacts the outer edge of the flange. Position the dial indicator with the contact point touching the "C" clamp. Remove play from gear teeth by turning the coupling flange. Set the dial indicator to zero and move flange in the opposite direction of the previous movement and note reading on dial indicator. Refer to Service Data for backlash limits. Backlash is adjusted by loosening the turbo-charger mounting bolts and repositioning the turbocharger on camshaft drive housing.

10. When the correct backlash is obtained, torque the 1/2" turbocharger and auxiliary drive mounting bolts to 88 N-m (65 ft-Ibs), the 3/4" bolts to 238 N-m (175 ft-lbs), and the 3/8" bolts to 32 N-m (24 ft-lbs). After the bolts are properly tightened, recheck the auxiliary drive gear backlash.

STARTING THE ENGINE

1. Make sure the soak back pump is running.

2. Make the necessary preparations and start the en-gine.

3. When starting the engine, do not force the injec-tor hand control lever beyond the idle position in an effort to aid the engine in starting. If the en-gine is forced on starting, the excess fuel and the resulting engine exhaust might cause an increase in load on the turbocharger thrust bearing when it should not be loaded.

4. Perform load test to qualify engine for service

EXHAUST MANIFOLD

DESCRIPTION
The exhaust gases from the engine cylinders are dis-charged from the cylinder heads into the exhaust mani-fold, Fig. 8-3, and to the turbocharger turbine. Going through the turbine, the gases expand to atmospheric pressure, pass through the turbocharger ducting, and are then expelled from the engine.
The exhaust manifold is made up of chamber assem-blies, expansion joints, and adapter assembly. The ex-pansion joints, which are used between chambeR assemblies and between the adapter and screen as-sembly and the turbocharger, provide the necessary flexibility to compensate for expansion and contrac-tion of the manifold due to temperature changes. The adapter assembly contains a trap type screen to prevent the entry of foreign objects into the turbo-charger. A trap box is attached to the outer body which collects small debris.

The exhaust manifold is essentially "maintenance free." but should the manifold be disassembled for any reason. the following assembly provisions should be observed

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