ME6412 ‐ THERMAL ENGINEERING LAB ‐ I
VALVE TIMING DIAGRAM FOR A FOUR STROKE DIESEL ENGINE
the cut section of a given
four stroke single cylinder, high speed diesel
engine mechanism and to draw the valve timing diagram.
Four stroke diesel engine test rig, 2. Measuring tape and 3. Chalk.
The four stroke engine has two valves namely Inlet valve and Exhaust valve. The cycle of
operation is completed in two revolutions of the crank shaft.
During suction stroke, only air is charged into the cylinder. Theoretically this stroke is executed
for 180° of crank shaft rotation. In actual practice the suction stroke starts before TDC and continues
few degrees of crank rotation after BDC. It inter connects the piston and crank shaft & transmit
the gas forces from the piston to the crank shaft.
It converts the reciprocating motion of the piston into useful rotary motion. The balancing
mass are provided on the crank shaft for static, dynamic balancing of the rotating system.
Fitted into the slots rounded the piston to provided a tight seal between the piston and
cylinder walls, thus preventing leakages of combustion gases.
The cam shaft and its associated parts control the opening & closing of the 2 valves .
The associated parts are push rods, rocker arms, valve springs and tappets. The cam shaft is driven
by crank shaft then timing gear.
In order to achieve a uniform torque and inertia in the form of a wheel is attached to
the o/p shaft and this wheel is called fly wheel.