2.1 TWO STROKE ENGINE

The injection of fuel into the cylinder of the two stroke engine is handled in the same

manner as the four stroke engine. As the piston nears Top Dead Center (TDC) the fuel

injector delivers an atomized spray of fuel into the cylinder. The fuel combines with the

air and is ignited by the high temperature. Rotation of the crankshaft carries the piston

past TDC as the fuel begins to combust with the air. Combustion of the fuel and air

causes the pressure in the cylinder to rise rapidly. This pressure expands in all directions,

pushing the piston downwards with a greater force than it took to initially compress the

air. As in the four stroke engine, this force on the piston is converted into a rotary motion

on the crankshaft, providing a useable mechanical force.

OPERATION

Assuming that the piston is at the bottom of its stroke and just starting up, the air

intake ports and the exhaust valves will be open. Air under pressure enters the cylinder

through the liner ports, pushes the exhaust gases, remaining from the previous power

stroke, out through the exhaust valves and fills the cylinder with a fresh supply of air.

When the piston is 45° after bottom dead center, the air intake ports will be closed by the

piston. Shortly after the air intake ports are closed, the exhaust valves will also be closed,

and the fresh air will be trapped in the cylinder. Closing the exhaust valves after the

intake air ports provides for the greatest efficiency in cylinder scavenging of combustion

gases.

As the piston continues upward, it compresses the trapped air into a very small volume.

Just before the piston reaches top dead center, the fuel injector sprays fuel into the

cylinder. Ignition of the fuel is practically instantaneous, due to the temperature of the

compressed air trapped in the top of the cylinder. The fuel burns rapidly as the piston is

forced down on the power stroke of the piston. As shown in the timing diagram, the

piston continues downward in the power stroke until the exhaust valves open. The

exhaust valves are opened ahead of the air intake ports to permit most of the combustion

gases to escape and reduce the pressure in the cylinder. When the air intake ports are

uncovered by the piston at 45° B.B.D.C. as it continues downward, air from the air box

under pressure can immediately enter the cylinder, scavenging the remaining combustion

gases from the cylinder and providing fresh air for combustion. The piston is again at the

original starting point and the cycle of events is repeated.

OPERATION OF ENGINE

V-ENGINE ARRANGEMENT The two stroke Electro-Motives diesel engine is a " Narrow V" type design

consisting of two rows of engine cylinders arranged with an angle of 45º between them.

Opposing cylinders share a common crankshaft eccentric. The rear of the engine is

usually called the flywheel end since this is where the main generator is driven from. The

camshaft gear train and auxiliary generator drive are located on the rear of the engine.

Engine rotation is left hand, or anti-clockwise as viewed from the rear facing towards the

front. The front end of the engine is commonly referred to as the governor end as this is

the mounting location of this device. The water pumps , lube oil pumps, and the pump

drive gears are also located on the front of the engine. Opposing cylinders are always

timed 45º apart. All oil, fuel, and cooling water connections for the engine are made on

the front end. A drive connection is available on the front end of the crankshaft for

accessory items such as air compressors, additional pumps, or mechanically driven

blowers.

Engine orientation is established from the rear of the engine looking forward.

The engine banks are termed left and right as viewed from the rear of the engine looking

forward. The cylinders are numbered sequentially from front to rear beginning with the

right bank. Cylinder number one is always located on the right front corner of the engine.

On a sixteen cylinder engine the cylinders on the right bank are numbered one thru eight

beginning with the right front; the cylinders on the left bank are numbered nine thru

sixteen beginning with the left front. On a 16 cylinder engine, for instance, the cylinders

are numbered one to eight on the right bank, starting with the front right. On the left bank

of the engine the cylinders are numbered nine to sixteen, starting with the front left. This

gives us pairs of cylinders such as 1 and 9, 8 and 16. Opposing cylinders fire 45 degrees

of crankshaft rotation apart due to the 45 degree "V" layout of the engine. A 16 cylinder

engine has one cylinder firing every 22 -1/2 degrees of crankshaft rotation (360/16).

Since the timing between each power pulse is equal (22 1/2 degrees), the 16 cylinder

engine has a balanced firing order. The firing order for a 16 cylinder example engine is 1,

8, 9, 16, 3, 6, 11, 14, 4, 5,12, 13, 2, 7, 10, 15. The exhaust system is located on the top of

the engine between the cylinder banks. For engines equipped with mechanical blowers,

the exhaust is collected in the manifold and allowed to vent to atmosphere.

2.1.2 PARTS OF A LOCOMOTIVE ENGINE

1 ENGINE EQUIPPED 2 CRANKCASE AND OIL PAN ASSEMBLY

3 HANDHOLE COVER 4 POWER ASSEMBLY

5 FUEL INJECTOR 6 ROCKER ARMS AND INJECTOR LINKAGE

7 CRANKSHAFT AND BOLT-ON EQUIPMENT

8 STARTER MOTOR 9 CAMSHAFT EQUIPMENT

10 OVERSPEED TRIP LINKAGE AND EQUIPMENT

11 LUBE OIL SYSTEM AND PUMPS

12 COOLING SYSTEM AND PUMPS

13 FUEL PIPING AND FILTER

14 GOVERNOR BOOSTER PUMP ASSEMBLY

15 CYLINDER HEAD COVERS AND SUPPORT FRAMES

16 ACCESSORY DRIVE HOUSING

17 PRESSURE DETECTOR APPLICATION

18 AUXILIARY GENERATOR DRIVE

19 GOVERNOR

20 GOVERNOR DRIVE EQUIPMENT

21 EXHAUST CHAMBER AND HEAT SHIELD

22 TURBOCHARGER

2.1.3 VARIOUS COMPONENTS OF V-ENGINE

POWER ASSEMBLY

FUEL OIL SYSTEM

COOLING WATER SYSTEM

LUBE OIL SYSTEM

AIR INTAKE SYSTEM

COMPRESSED AIR SYSTEM

2.2.1 POWER ASSEMBLY

Each cylinder of the diesel engine consists of a power pack or power assembly which is

made up of the following parts:

• cylinder liner

• cylinder head

• piston and rings

• piston carrier assembly

• connecting rod assembly

CYLINDER LINER

The cylinder liner is a cast iron assembly with brazed on outer sleeves. The unit

comprises the cylinder itself, cylinder water jacket, and intake ports. The intake ports are

arranged in a row around the circumference of the liner. This arrangement ensures

complete cylinder scavenging. Coolant enters the liner from a water manifold in the air

box, through a water jumper, into a flanged connection on the front lower side of the

liner. Inside the water inlet is a deflector that prevents erosion and cold spots on the liner.

CYLINDER HEAD

The cylinder head is a cast iron component, with passages for coolant and exhaust gases.

Four exhaust valves control the flow of gases from the cylinder, through the passages,

into the exhaust runner in the crankcase. These valves are run in replaceable nitride valve

guides, and held in place by valve springs and keepers. The bottom of the head forms the

top of the cylinder and the mating surface with the top of the liner. Twelve passages

around the outer diameter allow coolant to flow from the liner to the cylinder head. The

coolant flows over the inside of the cylinder head around the valve guide bores and

injector well, and exits the head by a discharge elbow into the engine block. From there

the coolant is collected from all cylinders and flows to the radiators.

PISTON AND PISTON RINGS

The pistons in EMD engines are a cast iron alloy. The undercrown of the piston is cooled

by lubricating oil supplied by the piston cooling section of the main lube oil pump to the

piston cooling pipes. This oil circulates from the piston cooling pipes through the piston

carrier to the fins in the undercrown area to remove combustion heat from the piston

crown area. The piston has four compression rings on the upper portion to seal the

cylinder from the crankcase. These rings are either ductile steel for use with chrome

plated liners, or chrome plated for use with cast iron finished liners. Two oil control rings

are positioned on the lower portion of the piston skirt to control liner lubrication and

prevent excess oil consumption.

PISTON CARRIER

The piston rides on a "trunnion" type carrier assembly. The carrier is fitted inside the

piston, and a thrust washer on top of the carrier allows the piston to rotate freely in the

cylinder. The piston is retained by a large snap ring fitting into a groove in the lower

inside piston skirt. The snap ring is not loaded during normal operation as the piston is

driven downward with each power stroke. If an injector is cut out or a cylinder is not

firing, the snap ring is loaded as it must pull the piston down.

CONNECTING ROD

The piston is retained by a large snap ring fitting into a groove in the lower inside piston

skirt. The snap ring is not loaded during normal operation as the piston is driven

downward with each power stroke. If an injector is cut out or a cylinder is not firing, the

snap ring is loaded as it must pull the piston down. The connecting rods consist of fork

rods, blade rods, basket halves, and a set of connecting rod lower bearings with the piston

pins bolted directly to the connecting rods.

CYLINDER HEAD

The cylinder head is a cast iron component, with passages for coolant and exhaust gases.

Four exhaust valves control the flow of gases from the cylinder, through the passages,

into the exhaust runner in the crankcase. These valves are run in replaceable nitrided

valve guides, and held in place by valve springs and keepers. The bottom of the head, or

fireface, forms the top of the cylinder and the mating surface with the top of the liner.

Twelve passages around the outer diameter of the fireface allow coolant to flow from the

liner to the cylinder head. The coolant flows over the inside of the fireface, around the

valve guide bores and injector well, and exits the head by a discharge elbow into the

engine block. From there the coolant is collected from all cylinders and flows to the

radiators. The top of the head is machined for mounting of the injector, rocker arm

assembly, and power assembly hold down crabs. The fuel injector is held in the injector

well by a hold down crab, and is clamped against a copper seal in the bottom of the well

to prevent combustion/compression leakage from the cylinder.

ROCKER ARM ASSEMBLY

The rocker arm assembly acts as an operating mechanism for the exhaust valves and fuel

injector and is held in place by two studs on the top of the head. There are three rocker

arms per cylinder; two exhaust and one injector (centre arm). Rollers on one end of the

rocker arms follow lobes on the camshaft. Force from the camshaft is transmitted to the

fuel injector, and to two valve bridges (one on each side of the injector). Each valve

bridge has two hydraulic lash adjusters that open the exhaust valves and maintain proper

valve adjustment.

REAR GEAR TRAIN

The rear gear train provides power to drive the camshafts and, depending on engine

model, the

blowers/or turbocharger. The gear train is located on the rear, or flywheel end of the

engine

and consists of:

• crankshaft gear

• #1 (or lower) idler gear

• #2 (or upper) idler gear

• left and right camshaft gears

• turbo drive gear or;

• blower drive gears

The camshafts are driven at a 1:1 ratio, they make one revolution every revolution of the

crankshaft.

The camshafts are driven off the #2 idler gear. The left bank camshaft gear meshes with

the #2 idler and then drives the right bank camshaft. The camshafts therefore rotate in

opposite directions inboard towards each other. The #2 idler has an extra row of teeth that

are used to drive the turbocharger. The idler stub shaft bracket provides a mounting

fixture for the idler gears and is bolted to the rear of the engine block. This bracket also

contains oil passages to direct lubricating oil from the oil gallery in the engine block to

the rear gear train, camshafts and turbo if equipped.

CLUTCH/SPRING DRIVE GEAR

On turbocharged engines there are two types of number 2 idler gear / turbo drive gear

assemblies, the spring drive gear, and the clutch drive gear. On turbocharged engines

there are two types of number 2 idler gear / turbo drive gear assemblies, the spring drive

gear, and the clutch drive gear. The clutch drive gear, introduced on the 710 engine is

similar to design and function to the internal turbo clutch, but is larger and much

stronger. Another advantage to this design is that this clutch can be removed and

inspected or rebuilt without disassembling the turbocharger. The spring drive gear is used

on engines with internal clutch turbochargers to absorb torsional vibration and cushion

the gear train from the shock loads of the turbo clutch engaging and disengaging. On

right hand rotation applications, the #2 idler gear drives the right bank camshaft gear,

which keeps the camshaft gear rotation inboard towards each other. Right

hand rotation engine turbochargers have an extra idler gear added so the turbo rotates the

same direction as a left hand rotation engine turbocharger.

ACCESSORY DRIVE

The accessory drive gear train is located at the front, or governor end of the engine and is

used to power the oil pumps, water pumps, and governor.

The components are:

• accessory drive gear

• scavenging oil pump gear

• main lube and piston cooling pump gear

• governor drive gear

• water pump gears

The accessory drive gear is a coil spring dampened gear assembly that provides a smooth

flow of power from the crankshaft to the accessory gears. The scavenging pump drive

gear is powered directly off this gear, as is the main lube and piston cooling pump drive

gear. The governor drive gear is mounted on a stub shaft assembly above the main lube

drive gear. As the main lube pump drive gear is rotated by the accessory drive gear, the

governor drive gear turns, powering the governor and the left and right water pump drive

gears. The governor angle drive is splined onto the center of the governor drive gear. The

gear train is enclosed by the accessory drive housing which provides mounting fixtures

for the pumps and governor.