Engine Design

Cylinder And Valve Location

Fuel System

General

FUEL FLOW SCHEMATIC (3512 Illustrated)
1. Fuel manifolds. 2. Fuel priming pump. 3. Pressure regulating valve. 4. Fuel injectors. 5. Fuel filters. 6. Fuel transfer pump. 7. Fuel return to supply.

Fuel transfer pump (6) is located on the right side of the engine. The lower shaft of engine oil pump (12) drives the gear type transfer pump. Fuel from the supply tank goes in the transfer pump at elbow (8).

The transfer pump has a check valve and a bypass valve. The check valve is located in the pump head assembly behind where line (10) is connected. The check valve prevents fuel flow back through the transfer pump when fuel priming pump (2) is used. The bypass valve is located behind cap (11). The bypass valve limits the maximum pressure of the fuel. It will open the outlet side of the pump to the pump inlet if the fuel pressure goes up to 860 kPa (125 psi). This helps prevent damage to fuel system components caused by too much pressure.

The transfer pump pushes fuel through fuel filters (5) to fuel manifolds (1). The fuel manifolds have two sections. The fuel flows through the top section of the manifold to tubes connected to the right side of each cylinder head. On earlier engines, filter screens are located in the fittings where fuel goes into each cylinder head. On later engines, the filter screens are located in the ports of the unit injector. A drilled passage (15) in cylinder head (16) takes fuel to a circular (shape of a circle) chamber around the injector. The chamber is made by O-rings on the outside diameter of fuel injector (4) and the injector bore in the cylinder head.

RIGHT SIDE OF ENGINE
6. Fuel transfer pump. 8. Elbow (fuel supply). 9. Fuel line to priming pump. 10. Fuel line to fuel filter base. 11. Cap (plug) for bypass valve. 12. Engine oil pump.

FUEL FLOW THROUGH INJECTOR
4. Injector. 13. Outlet fuel line. 14. Inlet fuel line. 15. Drilled passage. 16. Cylinder head. 17. Cylinder.

Only part of the fuel in the chamber is used for injection. Approximately 4 1/2 times as much fuel as needed for normal combustion flows through the chamber to a drilled passage in the left side of the cylinder head. This passage is connected by outlet fuel line (13) to the bottom section of the fuel manifold. This constant flow of fuel around the injectors helps to cool them.

CYLINDER HEADS
4. Fuel injector. 13. Outlet fuel line. 14. Inlet fuel line.

The fuel flows back through the bottom section of each fuel manifold to pressure regulating valve (3), on the front of the right fuel manifold. The fuel flows through this valve and then back to the tank.

Check each engine installation for an excess fuel flow based on fuel consumed (used for combustion). Minimum flow is three times the amount of fuel consumed. Excess fuel is then returned to the fuel tank, not back to the pump inlet. This will make sure that any air in the system will be removed before the fuel is sent back to the injectors.

Pressure regulating valve (3) has a spring and plunger arrangement between the bottom section of the fuel manifolds and the line that returns fuel to the tank. This valve keeps the pressure of the fuel at 415 to 450 kPa (60 to 65 psi) in the cylinder heads and fuel manifolds. The valve also has resistance to fuel flow but little resistance to air. This helps remove (bleed) air from the fuel injection system when the engine is in operation. The air is returned to the fuel tank and vented to the atmosphere.

A small orifice connects the inlet and outlet passages in the adapter (housing) of pressure regulating valve (3). The orifice is used as a syphon break when the fuel filters are changed. This keeps the fuel lines and manifolds from being drained and the use of fuel priming pump (2) is not normally needed. The fuel priming pump must be used when the lines are dry. For example: after an overhaul or other major fuel system work.

RIGHT SIDE OF ENGINE
1. Fuel manifold (right hand). 2. Fuel priming pump. 3. Pressure regulating valve. 5. Fuel filters.

Fuel Injection Control Linkage

FUEL INJECTOR CONTROL LINKAGE
1. Injector. 2. Control shaft (left side). 3. Bellcrank. 4. Control rod. 5. Rack. 6. Lever. 7. Governor shaft. 8. Control shaft (right side). 9. Cross shaft.

A fuel injector (1) is located in each cylinder head. The position of rack (5) controls the amount of fuel injected into the cylinder. Pull the rack out of the injector for more fuel, push it in for less fuel.

Rack position is changed by bellcrank (3). The bellcrank is moved by control rod (4). The control rods have an adjustment screw on the top. The adjustment screw is used to synchronize the injectors. The control rods are spring loaded. If the rack of one injector sticks (will not move), it will still be possible for the governor to control the other racks so the engine can be shutdown. Each control rod on the right side of the engine is connected by a lever (6) to control shaft (8).

When the rotation of governor shaft (7) is clockwise, as seen from in front of the engine, the action of the governor linkage moves control shaft (8) counterclockwise. That is, in the fuel "ON" direction.

Right control shaft (8) and left control shaft (2) are connected by cross shaft (9). The linkage between the injectors on the left side of the engine and control shaft (2) is similar to the linkage on the right side.

Should the linkage become disconnected from the governor, the weight of the control linkage will move the fuel injector racks to the fuel "SHUTOFF" position, and the engine will stop.

CYLINDER HEAD (Rocker Shaft Removed for Photo Illustration)
1. Injector. 3. Bellcrank. 5. Rack.

Fuel Injector

The injector is held in position by clamp (3). Fuel is injected when rocker arm (2) pushes the top of the injector down. The movement of the rocker arm is controlled by the camshaft through lifter assembly (7) and push rod (4). The amount of fuel injected is controlled by rack (5). Movement of the rack causes rotation of a gear fastened to plunger (6). Rotation of the plunger changes the effective stroke (that part of the stroke during which fuel is actually injected) of the plunger.

Injection timing is a product of two factors; the angular location of camshaft (8) and the location of plunger (6). The angular location of the camshaft is controlled by the camshaft drive gears at the rear of the engine. The location of the plunger can be adjusted with screw (1).

Injection Cycle

When the plunger is at the top of its stroke, fuel flows from the fuel supply chamber, around the injector and through both the lower and upper ports of the barrel. As plunger (6) is moved down by rocker arm (2), fuel is pushed back into the supply chamber through the lower port. The fuel can now go up through a passage in the center of the plunger and out through the upper port of the barrel. As the lower port is closed by the lower scroll on plunger (6), fuel can still flow through the upper port until it is closed by the upper scroll on plunger (6). At this point, injection starts and the effective stroke begins. During the effective stroke, fuel is injected into the cylinder until the downward movement of plunger (6) causes the lower scroll to open the lower port and release the fuel pressure.

Fuel then goes through the center passage of plunger (6) and the lower port during the remainder of the downstroke. This sudden release of pressure as the lower port is opened causes the fuel to hit the spill deflector with a high force. The spill deflector gives protection to the injector housing (nut) from erosion (wear) because of the force of the released fuel. On the return (UP) stroke, the chamber inside the injector barrel is filled with fuel again.

The plunger can be turned by rack (5) at the same time it is moved up and down by rocker arm (2). The upper section of the plunger has a flat side that fits in the gear, which is engaged with the rack. The plunger slides up and down in the gear, which also has a flat side on its inside diameter. The flat sides let the parts turn together. The rack is engaged with the gear. When the rack moves, it turns the plunger through the gear. The rotation of plunger (6) controls injection timing and the fuel output of the injector. Rotation of the plunger changes the relation of the plunger scrolls to the ports in the barrel, and this increases or decreases the length of the effective stroke and the point at which injection takes place.

When rack (5) is moved all the way in against the injector body, no injection takes place during the downstroke of the plunger. This is the fuel "SHUTOFF" position. A small amount of rack movement "OUT" from the injector body is used as a "NO FUEL" movement or "SHUTOFF" position for governing purposes. This "NO FUEL" distance starts at the "ALL-THE-WAY-IN" position of the rack, and ends when the lower scroll opens the lower port and the upper scroll closes the upper port. Movement of the rack "OUT" from this point in the fuel "ON" direction, gives an interval in the plunger stroke when both ports are closed by the scrolls and injection takes place. As the rack is moved farther "OUT" in the fuel "ON" direction, the quantity of fuel during the injection stroke increases until a maximum is available at full rack movement.

The scrolls on plunger (6) are used to time the start of injection and set the amount of fuel per injection stroke. The scrolls can change the start of injection in relation to the engine piston position and the length of the effective stroke in relation to the different engine loads. The start of injection can be retarded (made later) with a decrease or increase in injector output according to the engine needs.

During the fuel injection stroke, fuel passes from the barrel chamber through a valve assembly. The valve assembly has a spring-loaded needle valve with a cone shaped end which operates against a seat. The angle of the valve is slightly larger than that of the seat to give line contact. The valve opens at approximately 20 000 to 23 300 kPa (2800 to 3400 psi) and closes at approximately 10 300 kPa (1500 psi). The fuel flows from the chamber inside the barrel through drilled passages and grooves in the spring cage, and then through passages around the guide section of the valve to the valve chamber. Here the fuel pressure lifts the needle valve off its seat, and the fuel now flows through the spray tip and out the orifices into the combustion chamber.

FUEL INJECTOR OPERATION
1. Screw. 2. Rocker arm. 3. Clamp. 4. Control rod. 5. Rack. 6. Plunger. 7. Lifter assembly. 8. Camshaft.

A flat check valve is used above the needle valve to keep the high pressure combustion gases out of the injector. If the needle valve is held open by small foreign particles for a moment between injection cycles, combustion gases can come into the injector and cause damage. The injector operates with the flat check valve until the foreign particle has washed on through and normal operation takes place.

The spray tip of the injector extends a short distance below the cylinder head into the combustion chamber. The spray tip has several small orifices spaced evenly around the outside diameter. The tip sprays fuel into the combustion chamber. The top surface of the piston has a shaped (mexican hat-type) crater. The design of the piston causes rotation of the air as it comes through the valves into the combustion chamber, which improves the mixture of the fuel and air.

Woodward UG8 Lever Governors

SCHEMATIC OF UG8 LEVER GOVERNOR

The Woodward UG8L is the standard governor used on Industrial Engines. Standard location for the governor is on the right side of the front housing; with an attachment gear group it can be located on the left side.

The UG8 Lever Governor is a mechanical-hydraulic governor. A hydraulic activated power piston is used to turn the output terminal shaft of the governor. The terminal shaft is connected by linkage to the fuel control torsion shafts. The rotation of the fuel control torsion shafts controls rack movement at each fuel injector. Make reference to FUEL INJECTOR CONTROL LINKAGE. The governor oil pump and ballhead are driven by a bevel gear set in the governor drive housing. The bevel gear set is driven by the front gear group.

The oil pump gives pressure oil to operate the power piston. The drive gear of the oil pump has a bushing in which the pilot valve plunger moves up and down. The driven gear of the oil pump is also the drive for the ballhead.

An accumulator is used to keep a constant oil pressure of approximately 830 kPa (120 psi) to the top of the power piston and to the pilot valve.

The power piston is connected by a linkage system to one side of the output terminal shaft. There is oil pressure on both the top and bottom of the power piston. The bottom of the piston has a larger area than the top.

Less oil pressure is required on the bottom than on the top to keep the piston stationary. When the oil pressure is the same on the top and bottom of the piston, the piston will move up and cause the output terminal shaft to turn in the increase fuel direction. When oil pressure on the bottom of the piston is directed to the sump (drain), the piston will move down and cause the output terminal shaft to turn in the decrease fuel direction. Oil to or from the bottom of the power piston is controlled by the pilot valve.

The pilot valve has a plunger and bushing. The bushing is turned by the governor drive shaft. The rotation of the bushing helps reduce friction between the bushing and plunger. The pilot valve plunger has a land that controls the oil flow through the ports in the bushing. When the pilot valve plunger is moved down, high pressure oil goes to the bottom of the power piston and the power piston will move up. When the pilot valve plunger is moved up, the oil on the bottom of the power piston is released to the sump and the power piston moves down. When the pilot valve plunger is in the center (balance) position, the oil port to the bottom of the power piston is closed and the power piston will not move. The pilot valve plunger is moved by the ballhead assembly.

The ballhead assembly has a ballhead, flyweights, speeder spring, thrust bearing, speeder plug and speeder rod. The ballhead assembly is driven by a gear and shaft from the driven gear of the oil pump. The speeder rod is fastened to the thrust bearing which is in contact with the flyweights. The speeder rod is connected to the pilot valve plunger by a lever. The speeder spring is held in position on the thrust bearing by the speeder plug.

As the ballhead turns, the flyweights move out due to centrifugal force. This will make the flyweight toes move up and cause compression of the speeder spring. When the force of the speeder spring and the force of the flyweights are equal the engine speed is constant. The speeder plug can be moved up or down manually to change the compression of the speeder spring which will change the speed of the engine.

The compensation system gives stability to engine speed changes. The compensation system has a needle valve and two pistons-an actuating piston and a receiving piston. The actuating piston is also connected to the output terminal shaft by the compensation adjusting lever and linkage system. A fulcrum that is adjustable is on the lever. When the position of the fulcrum is changed, the amount of movement possible of the actuating piston is changed.

The receiving piston is connected to the pilot valve plunger and the speeder rod by a lever.

The needle valve makes a restriction to oil flow between the oil sump and the two pistons.

When the actuating piston moves down, the piston puts a force on the oil under the receiving piston and moves it up. When the receiving piston moves up it raises the pilot valve plunger to stop the flow of oil to the bottom of the power piston.

When the engine is in operation at a steady speed the land on the pilot control valve is in the center of the control port of the bushing. A decrease in load will cause an increase in engine speed. With an increase in engine speed the flyweights move out and raise the speeder rod and floating lever. This raises the pilot valve plunger and releases oil from the bottom of the power piston. As the power piston moves down, the output terminal shaft moves in the decrease fuel direction. When the output terminal shaft moves, the actuating compensation piston moves up and causes a suction on the oil under the receiving piston which moves down. The floating lever is pulled down by the receiving piston and the lever moves the pilot control valve down to close the control port. The output terminal shaft and power piston movement is stopped. As the engine speed returns to normal, the flyweights move in and the speeder rod moves down. When the oil pressure in the compensation system and the sump oil become the same through the needle valve, the receiving compensation piston moves up at the same rate as the speeder rod moves down. This action keeps the pilot valve plunger in position to close the port.

An increase in load will cause a decrease in engine speed. When engine speed decreases, the flyweights move in and lower the speeder rod and floating lever. This lowers the pilot valve plunger and lets pressure oil go under the power piston. The power piston moves up and turns the output terminal shaft in the increase fuel direction. When the output terminal shaft moves, the actuating compensation piston moves down and causes a pressure on the receiving piston which moves up. The floating lever is pushed up by the receiving piston and the lever moves the pilot valve plunger up to close the control port. The output terminal shaft and power piston movement is stopped.

A change to the speed setting of the governor will give the same governor movements as an increase or decrease in load.

A lever on the speed adjustment shaft is used to change the engine speed. The speed adjustment shaft moves the speeder plug up and down to change the force of the speeder spring.

This governor is also equipped with speed droop, however, it must be adjusted inside the governor.

UG8 LEVER GOVERNOR
1. Fuel ratio control. 2. Governor. 3. Governor drive.

Fuel Ratio Control

The fuel ratio control is installed on top of the basic UG8L Governor. The unit is made up of an inlet manifold pressure sensor, a hydraulic circuit and mechanical linkage that connects the unit to the governor. Pressure oil from the governor hydraulic system is used to operate the unit.

When engine speed or load is increased rapidly, it is possible for a standard (unlimited) governor to supply more fuel than can be burned with the amount of available air. Too much smoke and poor acceleration are the result. The fuel ratio control works to limit the movement of the governor terminal shaft in the increase fuel direction as a direct result of inlet manifold pressure. Thus, fuel which can be burned is limited to the air available for combustion as the engine speed is increased. This gives more complete combustion and keeps smoke to a minimum while acceleration is improved.

The fuel ratio is also used for protection to limit the fuel as the result of any large, sudden restriction of air supply to the engine.

Governor accumulator oil pressure is changed to a restricted variable (pulsating) oil flow as small holes (ports) in the pilot valve bushing move past a passage in the controlet housing. In a constant speed operation, the ball valve is not tight against its seat and lets oil flow back to the sump. The ball valve is held in position by the sensing bellows, which is connected to inlet manifold air pressure. The force used to hold the ball valve is proportional to the inlet manifold air pressure.

As inlet manifold air pressure increases, the ball valve makes contact with its seat and oil pressure increases to move the limiter piston to the right against the force of the restoring spring. This movement increases the tension on the restoring spring until the spring force is in balance with the sensing bellows force. The oil pressure now can push the ball valve off its seat and let a small amount of oil flow to the sump. This reduces the pressure behind the limiter piston and the piston stops movement. The piston position is proportional to inlet manifold air pressure.

The cam fastened to the limiter piston operates through linkage to limit the travel of the governor terminal shaft. The governor terminal shaft limits the fuel to the engine through the fuel control linkage. The terminal shaft can turn in the increase fuel direction until the pivot lever lifts the pilot valve above center. Oil pressure on the bottom of the power piston is now directed to the sump. The power piston moves down and causes the terminal shaft to turn in the decrease fuel direction.

When the engine is stopped, the limiter piston is held to the left by the restoring spring. The fuel limit valve at this position is set high enough by the cam to give enough fuel for start up. At cranking speed, oil pressure behind the limiter piston goes by the diaphram to the sump. After the engine has started, engine lubrication oil pressure pushes the diaphram against its seat and closes the governor oil drain. Oil pressure now increases behind the limiter piston. The limiter piston moves out until the roller follower is on the operating slope of the cam. At this point the ball valve is moved off its seat, the oil can now flow to sump and the piston movement is stopped.

SCHEMATIC OF FUEL RATIO CONTROL SYSTEM

Air Inlet And Exhaust System

The components of the air inlet and exhaust system control the quality and amount of air available for combustion. There is a separate turbocharger and exhaust manifold on each side of the engine. A common aftercooler is located between the cylinder heads in the center of the engine. The inlet manifold is a series of elbows that connect the aftercooler chamber to the inlet ports (passages) of the cylinder heads. Two camshafts, one in each side of the block, control the movement of the valve system components.

AIR INLET AND EXHAUST SYSTEM
1. Exhaust manifold. 2. Aftercooler. 3. Engine cylinder. 4. Air inlet. 5. Turbocharger compressor wheel. 6. Turbocharger turbine wheel. 7. Exhaust outlet.

Air flow is the same on both sides of the engine. Clean inlet air from the air cleaners is pulled through air inlet (4) by compressor wheel (5). The rotation of the compressor wheel causes compression of the air and forces it through a pipe to aftercooler (2). The aftercooler lowers the temperature of the compressed air before it goes into the inlet chambers in each cylinder head. This cooled, compressed air fills the inlet chambers in the cylinder heads. Air flow from the inlet chamber into the cylinder is controlled by the intake valves.

There are two intake and two exhaust valves for each cylinder. Make reference to Valve System Components. The intake valves open when the piston moves down on the inlet stroke. Cooled compressed air from the inlet chamber is pulled into the cylinder. The intake valves close and the piston starts to move up on the compression stroke. When the piston is near the top of the compression stroke fuel is injected into the cylinder. The fuel mixes with the air and combustion starts. The force of combustion pushes the piston down on the power stroke. When the piston moves up again it is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into exhaust manifold (1). After the piston makes the exhaust stroke the exhaust valves close and the cycle (inlet, compression, power, exhaust) starts again.

Exhaust gases from the exhaust manifold go into the turbine side of each turbocharger (8) and cause turbine wheel (6) to turn. The turbine wheel is connected to the shaft that drives compressor wheel (5). The exhaust gases then go out the exhaust outlet (7).

AIR SYSTEM COMPONENTS
1. Exhaust manifolds. 2. Aftercooler. 8. Turbochargers.

AIR FLOW SCHEMATIC
1. Exhaust manifolds. 2. Aftercooler. 3. Engine cylinder. 4. Air inlet. 7. Exhaust outlet. 8. Turbocharger. 9. Air transfer pipe.

Aftercooler

The aftercooler is located at the center of the vee. The aftercooler has a coolant charged core assembly. The 3516 can have two core assemblies. Coolant from water pump (3) flows through pipe (2) into the aftercooler. It then flows through the core assembly and out of the aftercooler through a different pipe into the rear of the cylinder block.

There is a connector (tube) that connects the bottom rear of the core assembly to the cylinder block. This is used to drain the aftercooler when the coolant is drained from the engine.

Inlet air from the compressor side of the turbochargers flows into the aftercooler through pipes. The air passes through the core assembly which lowers the temperature. The cooler air goes out the bottom of the aftercooler into the air chamber then up through the elbows to the inlet ports (passages) in the cylinder heads.

RIGHT FRONT OF ENGINE
2. Pipe. 3. Water pump.

TOP OF ENGINE
1. Aftercooler housing.

AFTERCOOLER AIR CHAMBER DRAIN
4. Drain plug.

One drain plug is located between the No. 1 and 3 cylinder heads and another plug is located between the last two cylinder heads on the left side of the engine. These plugs can be removed to check for water or coolant in the aftercooler air chamber.

Turbochargers

There are two turbochargers, one on each side of the engine. The turbine side of the turbochargers is fastened to the exhaust manifolds. The compressor side of the turbocharger is connected to the aftercooler.

TURBOCHARGERS
1. Turbocharger. 2. Oil drain line. 3. Oil supply line.

The exhaust gases go into turbine housing (8) and push the blades of turbine wheel (9). This causes the turbine wheel and compressor wheel to turn at up to 70,000 rpm.

TURBOCHARGER (3512 Shown)
4. Compressor wheel. 5. Bearing. 6. Oil inlet. 7. Bearing. 8. Turbine housing. 9. Turbine wheel. 10. Air inlet. 11. Oil outlet.

Clean air from the air cleaners is pulled through the compressor housing air inlet (10) by rotation of compressor wheel (4). The action of the compressor wheel blades causes a compression of the inlet air. This compression gives the engine more power because it makes it possible for the engine to burn additional fuel with greater efficiency.

Maximum rpm of the turbocharger is controlled by the fuel setting, the high idle rpm setting and the height above sea level at which the engine is operated.

The bearings (5 and 7) in the turbocharger use engine oil under pressure for lubrication. The oil comes in through oil inlet port (6) and goes through passages in the center section for lubrication of the bearings. Then the oil goes out oil outlet port (11) and back to the oil pan.

Valve System Components

The valve system components control the flow of inlet air and exhaust gases into and out of the cylinders during engine operation.

The crankshaft gear drives the camshaft gears through idlers. Both camshafts must be timed to the crankshaft to get the correct relation between piston and valve movement.

VALVE SYSTEM COMPONENTS
1. Rocker arm. 2. Bridge. 3. Rotocoil. 4. Valve spring. 5. Push rod. 6. Lifter.

The camshafts have three cam lobes for each cylinder. Two lobes operate the valves and one operates the fuel injector.

As each camshaft turns the lobes on the camshaft cause lifters (6) to go up and down. This movement makes push rods (5) move the rocker arms (1). Movement of the rocker arms makes the bridges (2) move up and down on dowels in the cylinder head. The bridges let one rocker arm open and close two valves (intake or exhaust). There are two intake and two exhaust valves for each cylinder.

Rotocoils (3) cause the valves to turn while the engine is running. The rotation of the valves keeps the deposit of carbon on the valves to a minimum and gives the valves longer service life.

Valve springs (4) cause the valves to close when the lifters move down.

Lubrication System

LUBRICATION SYSTEM SCHEMATIC (3512 System Illustrated)
1. Main oil gallery. 2. Left camshaft oil gallery. 3. Piston cooling jet gallery. 4. Piston cooling jet gallery. 5. Right camshaft oil gallery. 6. Sequence valve. 7. Turbocharger oil drain line. 8. Oil filter base. 9. Turbocharger oil supply. 10. Elbow. 11. Sequence valve. 12. Oil cooler. 13. Oil cooler bypass valve. 14. Oil pump relief valve. 15. Oil pump. 16. Elbow. 17. Suction bell.

This system uses an oil pump (15) with three gears that are driven by the front gear train. Oil is pulled from the pan through suction bell (17) and elbow (16) by the oil pump. The suction bell has a screen to clean the oil.

The oil pump pushes oil through oil cooler (12) and the oil filters to oil galleries (1 and 2) in the block. The fin and tube type oil cooler lowers the temperature of the oil before the oil is sent on to the filters.

Bypass valve (13) lets oil flow directly to the filters if the oil cooler becomes plugged or if the oil becomes thick enough (cold start) to increase the oil pressure differential (cooler inlet to outlet) by an amount of 180 ± 20 kPa (26 ± 3 psi).

Spin-on filters are located on the left side of the cylinder block. The oil filter base has one bypass valve (19) for each filter.

Clean oil from the filters goes into the block through elbow (10). Part of the oil goes to the left camshaft oil gallery (2) and part goes to the main oil gallery (1).

The camshaft galleries are connected to each camshaft bearing by a drilled hole. The oil goes around each camshaft journal, through the cylinder head and rocker arm housing, to the rocker arm shaft. A drilled hole connects the bores for the valve lifters to the oil hole for the rocker arm shaft. The lifters get lubrication each time they go to the top of their stroke.

Main oil gallery (1) is connected to the main bearings by drilled holes. Drilled holes in the crankshaft connect the main bearing oil supply to the rod bearings. Oil from the rear of the main oil gallery goes to the right camshaft oil gallery (5).

PISTON COOLING AND LUBRICATION
18. Cooling jet.

Sequence valves (6 and 11) let oil from main oil gallery (1) go to piston cooling jet oil galleries (3 and 4). The sequence valves open at 140 kPa (20 psi). The sequence valves will not let oil into the piston cooling jet oil galleries until there is pressure in the main oil gallery. This decreases the amount of time necessary for pressure build-up when the engine is started. It also helps hold pressure at idle speed.

There is a piston cooling jet (18) below each piston. Each cooling jet has two openings. One opening is directed at a passage in the bottom of the piston. This passage takes oil to a manifold behind the ring band of the piston. A slot (groove) is in the side of both piston pin bores and connects them with the manifold behind the ring band. The other cooling jet opening is directed at the center of the piston. This helps cool the piston and gives lubrication to the piston pin.

Oil lines (9) send oil to the turbochargers. The turbocharger oil drain lines (7) are connected to the camshaft housing covers on each side of the engine.

LEFT FRONT SIDE OF ENGINE (3512 Engine Shown)
8. Oil filter. 10. Elbow. 19. Oil filter bypass valve.

TURBOCHARGER OIL LINES (3512 Engine Shown)
7. Turbocharger oil drain line. 9. Turbocharger oil supply line.

Oil is sent to the front and rear gear groups through drilled passages in the front and rear housings and cylinder block faces. These passages are connected to camshaft oil galleries (2 and 5).

After the oil for lubrication has done its work, it goes back to the engine oil pan.

LEFT FRONT OF ENGINE (3512 Engine Shown)
7. Turbocharger oil drain line. 9. Turbocharger oil supply lines.

Cooling System

SCHEMATIC OF COOLING SYSTEM (3512 Shown)
1. Water pump. 2. Tube (to aftercooler). 3. Oil cooler. 4. Cylinder block. 5. Cylinder head. 6. Water manifold. 7. Aftercooler. 8. Regulator housing. 9. Tube (to radiator or heat exchanger). 10. Bypass tube.

This system uses a water pump (1) that is driven by the front gear train. Coolant goes in water pump (1) through an elbow that connects to the radiator or other heat exchanger. The coolant flow is divided at the outlet of the water pump. Part of the coolant flow is sent to the aftercooler, while most of the coolant is sent through the oil cooler.

NOTE: There is one opening on the pump outlet so that a remote pump can be connected to the system. The remote pump can be used if there is a failure of the pump on the engine.

Coolant sent to the aftercooler goes through the aftercooler core, and then is sent by an elbow into a passage in the block near the center of the vee at the rear of the block. The coolant sent to the oil cooler goes through the oil cooler and flows into the water jacket of the block at the right rear cylinder. The coolant mixes with the hotter coolant and goes to both sides of the block through distribution manifolds connected to the water jacket of all the cylinders. The main distribution manifold is located just above the main bearing oil gallery.

The coolant flows up through the water jackets and around the cylinder liners from the bottom to the top. Near the top of the cylinder liners, where the temperature is the hottest, the water jacket is made smaller. This shelf (smaller area) causes the coolant to flow faster for better liner cooling. Coolant from the top of the liners goes into the cylinder head which sends the coolant around the parts where the temperature is the hottest. Coolant then goes to the top of the cylinder head and out through an elbow, one at each cylinder head, into water manifolds (6) at each bank of cylinders. Coolant goes through the manifolds to the temperature regulator (thermostat) housing.

Regulator housing (8) has an upper and lower flow section, and uses four temperature regulators. The sensing bulbs of the four temperature regulators are in the coolant in the lower section of the housing. Before the regulators open, cold coolant is sent through the lower section of the housing and through the bypass line back to the inlet of the water pump. As the temperature of the coolant increases enough to make the regulators start to open, coolant flow in the bypass line is stopped and coolant is sent through the outlets to the radiator or heat exchanger.

Total system coolant capacity will depend on the size of the heat exchanger. Use a coolant mixture of 50 percent pure water and 50 percent permanent antifreeze, then add a concentration of 3 to 6 percent corrosion inhibitor.

RIGHT SIDE OF ENGINE
1. Water pump. 3. Oil cooler. 8. Regulator housing. 10. Bypass tube.

TOP OF ENGINE
6. Water manifolds. 7. Aftercooler.

Basic Block

Cylinder Block, Liners And Heads

The cylinders in the left side of the block make an angle of 60° with the cylinders in the right side of the block. The main bearing caps are fastened to the block with four bolts per cap.

The cylinder liners can be removed for replacement. The top surface of the block is the seat for the cylinder liner flange. Engine coolant flows around the liners to keep them cool. Three O-ring seals around the bottom of the liner make a seal between the liner and the cylinder block. A filler band goes under the liner flange and makes a seal between the top of the liner and the cylinder block.

The engine has a separate cylinder head for each cylinder. Four valves (two intake and two exhaust), controlled by a push rod valve system, are used for each cylinder. Valve guides without shoulders are pressed into the cylinder heads. The opening for the fuel injector is located between the four valves. A third lobe on the camshaft moves the push rod system that operates the fuel injector. Fuel is injected directly into the cylinder.

There is an aluminum spacer plate between each cylinder head and the block. Coolant goes out of the block through the spacer plate and into the head through eight openings in each cylinder head face. Water seals are used in each opening to prevent coolant leakage. Gaskets seal the oil drain passages between the head, spacer plate and block.

LEFT SIDE OF 3512 ENGINE
1. Covers for camshafts and fuel control linkage inspection. 2. Covers for crankshaft main and rod bearing inspection.

Covers (1) allow access to the camshafts, valve lifters and fuel control shaft.

Covers (2) allow access to the crankshaft connecting rods, main bearings and piston cooling jets. With covers removed, all the openings can be used for inspection and service.

Pistons, Rings And Connecting Rods

The aluminum pistons have an iron band for the top two rings. This helps reduce wear on the compression ring grooves. A chamber is cast into the piston just behind the top ring grooves. Oil from the piston cooling jets flows through this chamber to cool the piston and improve ring life. The pistons have three rings; two compression rings and one oil ring. All the rings are located above the piston pin bore. The oil ring is a standard (conventional) type. Oil returns to the crankcase through holes in the oil ring groove. The top two rings are the KEYSTONE type, which are tapered. The action of the ring in the piston groove, which is also tapered, helps prevent seizure of the rings caused by too much carbon deposit.

The connecting rod has a taper on the pin bore end. This gives the rod and piston more strength in the areas with the most load. Four bolts set at a small angle hold the rod cap to the rod. This design keeps the rod width to a minimum, so that a larger rod bearing can be used and the rod can still be removed through the liner.

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the machine. A vibration damper of the fluid type is used at the front of the crankshaft to reduce torsional vibrations (twist on the crankshaft) that can cause damage to the engine.

The crankshaft is symmetrical. This makes it possible to turn the crankshaft end for end when opposite engine rotation is desired.

The crankshaft drives a group of gears on the front and rear of the engine. The gear group on the front of the engine drives the oil pump, water pump, fuel transfer pump, governor and two accessory drives. The gear group on the rear of the engine drives the camshafts.

Lip seals and wear sleeves are used at both ends of the crankshaft for easy replacement and a reduction of maintenance cost. Pressure oil is supplied to all main bearings through drilled holes in the webs of the cylinder block. The oil then flows through drilled holes in the crankshaft to provide oil to the connecting rod bearings. The crankshaft is held in place by five main bearings on the 3508, seven main bearings on the 3512, and nine main bearings on the 3516. A thrust plate at either side of the center main bearing controls the end play of the crankshaft.

Camshafts

The engine has a camshaft or camshaft group for each side of engine, driven at the rear of the engine. Five bearings for the 3508, seven bearings for the 3512, and nine bearings on the 3516 support each camshaft or camshaft group. The 3512 and 3516 each use two camshafts per side that are doweled and bolted together to make a camshaft group. As the camshaft turns, each lobe moves a lifter assembly. There are three lifter assemblies for each cylinder. Each outside lifter assembly moves a push rod and two valves (either intake or exhaust). The center lifter assembly moves a push rod that operates the fuel injector. The camshafts must be in time with the crankshaft. The relation of the cam lobes to the crankshaft position cause the valves and fuel injectors in each cylinder to operate at the correct time.

Air Starting System

The air starting motor is used to turn the engine flywheel fast enough to get the engine running.

TYPICAL AIR STARTING SYSTEM
1. Air starting motor. 2. Relay valve. 3. Oiler.

The air starting motor can be mounted on either side of the engine. Air is normally contained in a storage tank and the volume of the tank will determine the length of time the engine flywheel can be turned. The storage tank must hold this volume of air at 1720 kPa (250 psi) when filled.

For engines which do not have heavy loads when starting, the regulator setting is approximately 690 kPa (100 psi). This setting gives a good relationship between cranking speeds fast enough for easy starting and the length of time the air starting motor can turn the engine flywheel before the air supply is gone.

If the engine has a heavy load which can not be disconnected during starting, the setting of the air pressure regulating valve needs to be higher in order to get high enough speed for easy starting.

The air consumption is directly related to speed; the air pressure is related to the effort necessary to turn the engine flywheel. The setting of the air pressure regulator can be up to 1030 kPa (150 psi), if necessary, to get the correct cranking speed for a heavily loaded engine. With the correct setting, the air starting motor can turn the heavily loaded engine as fast and as long as it can turn a lightly loaded engine.

Other air supplies can be used if they have the correct pressure and volume. For good life of the air starting motor, the supply should be free of dirt and water. A lubricator with SAE 10 nondetergent oil [for temperatures above 0°C (32°F)], or diesel fuel [for temperatures below 0°C (32°F)] should be used with the starting system. The maximum pressure for use in the air starting motor is 1030 kPa (150 psi). Higher pressures can cause safety problems.

TYPICAL AIR START INSTALLATION
4. Air start control valve.

The air from the supply goes to relay valve (2). The starter control valve (4) is connected to the line before the relay valve (2). The flow of air is stopped by the relay valve (2) until starter control valve (4) is activated. The air from starter control valve (4) goes to piston (10) behind pinion (8) for the starter. The air pressure on piston (10) puts spring (11) in compression and puts pinion (8) in engagement with the flywheel gear. When the pinion is in engagement, air can go out through another line to relay valve (2). The air activates relay valve (2) which opens the supply line to the air starting motor.

AIR STARTING MOTOR
5. Air inlet. 6. Vanes. 7. Rotor. 8. Pinion. 9. Gears. 10. Piston. 11. Piston spring.

The flow of air goes through the oiler (3) where it picks up lubrication oil for the air starting motor.

The air with lubrication oil goes into the air motor through air inlet (5). The pressure of the air pushes against vanes (6) in rotor (7), and then exhausts through the outlet at bottom of air motor. This turns the rotor which is connected by gears (9) and a drive shaft to starter pinion (8) which turns the engine flywheel.

When the engine starts running the flywheel will start to turn faster than starter pinion (8). Pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or flywheel gear.

When starter control valve (4) is released, the air pressure and flow to piston (10) behind starter pinion (8) is stopped, piston spring (11) retracts pinion (8). Relay valve (2) stops the flow of air to the air starting motor.

To maintain the efficiency of the starting motor, flush it at regular intervals. Put approximately 0.5 liter (1 pt.) of diesel fuel into the air inlet of the starting motor and operate the motor. This will remove the dirt, water and oil mixture (gummy coating) from the vanes of the motor.

Electrical System

The electrical system has three separate circuits: the charging circuit, the starting circuit and the low amperage circuit. Some of the electrical system components are used in more than one circuit. The battery (batteries), circuit breaker, ammeter, cables and wires from the battery are all common in each of the circuits.

The charging circuit is in operation when the engine is running. An alternator makes electricity for the charing circuit. A voltage regulator in the circuit controls the electrical output to keep the battery at full charge.

The starting circuit is in operation only when the start switch is activated.

The low amperage circuit and the charging circuit are both connected to the same side of the ammeter. The starting circuit connects to the opposite side of the ammeter.

Charging System Components

Alternator

The alternator is driven by V-type belts from the crankshaft pulley. This alternator is a three phase, self-rectifying charging unit, and the regulator is part of the alternator.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carry current are stationary. The conductors are: the field winding, stator windings, six rectifying diodes, and the regulator circuit components.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (like permanent magnets) that produce a small amount of magnet-like lines of force (magnetic field) between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the small magnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through the diodes of the recitifer bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent on to the field windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator.

ALTERNATOR

The voltage regulator is solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system, and switches on and off many times a second to control the field current (DC current to the field windings) to the alternator. The output voltage from the alternator will now supply the needs of the battery and the other components in the electrical system.

Starter System Components

Starter Motor

The starter motor is used to turn the engine flywheel fast enough to get the engine running.

The starter motor has a solenoid. When the start switch is activated, electricity will flow through the windings of the solenoid. The solenoid core will now move to push the starter pinion, by a mechanical linkage to engage with the ring gear on the flywheel of the engine. The starter pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starter motor. When the circuit between the battery and the starter motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starter motor so that the engine, when it starts to run, can not turn the starter motor too fast. When the start switch is releasd, the starter pinion will move away from the flywheel ring gear.

STARTER MOTOR
1. Field. 2. Solenoid. 3. Clutch. 4. Pinion. 5. Commutator. 6. Brush assembly. 7. Armature.

Starter Solenoid

A solenoid is a magnetic switch that causes low current to close a high current circuit. The solenoid has an electromagnet with a core (6) which moves.

There are contacts (4) on the end of core (6). The contacts are held in the open position by spring (5) that pushes core (6) from the magnetic center of coil (1). Low current will energize coil (1) and make a magnetic field. The magnetic field pulls core (6) to the center of coil (1) and the contacts close.

SCHEMATIC OF A SOLENOID
1. Coil. 2. Switch terminal. 3. Battery terminal. 4. Contacts. 5. Spring. 6. Core. 7. Component terminal.

Other Components

Circuit Breaker

The circuit breaker is a switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.

A heat activated metal disc with a contact point completes the electric circuit through the circuit breaker. If the current in the electrical system gets too high, it causes the metal disc to get hot. This heat causes a distortion of metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset after it cools. Push the reset button to close the contacts and reset the circuit breaker.

CIRCUIT BREAKER SCHEMATIC
1. Reset button. 2. Disc in open position. 3. Contacts. 4. Disc. 5. Battery circuit terminals.