The document describes an experiment to draw the valve timing diagram of a four-stroke single-cylinder diesel engine. Key steps include: 1) Marking the top dead center and bottom dead center positions on the flywheel. 2) Slowly rotating the flywheel and marking when the inlet and exhaust valves open and close. 3) Marking the fuel injection timing for diesel engines. 4) Measuring the valve and crank angles to plot the valve timing diagram.

1. Experiment No.5
Objective:
To study and draw the valve timings diagram Four-Stroke, Single-Cylinder Diesel Engine.
Apparatus Used :
Four-Stroke, Single-Cylinder Diesel Engine Test Rig, Sprit
Level,Marking Pencil, and Device for measuring crank angle.
Theory :
Fig 5.1 (Timings Diagram Four-Stroke Diesel Engine)
In four- stroke S. I. Engine the opening and closing of the valves, and the ignition of the air fuel
mixture do not take place exactly at the dead centre positions. The valve open slightlyearlier and
close after their respective dead centre positions. The ignition also occurs prior, to the mixture is
fully compressed, and the piston reaches the top dead centre position.Similarly in a C. I. Engine
both the valves do not open and close exactly at dead centre positions, rather operate at some

2. degree on either side in terms of the crank angles from the dead centre positions. The injection of
the fuel is also timed to occur earlier.
Procedure:
1. Fix a plate on the body of the Engine touching the flywheel.
2. Mark the positions of the both the dead centers on the flywheel with the reference to the
fixed plate. TDC and BDC in case of vertical Engines, IDC and ODC in case of
horizontal Engines.
3. Mark on the flywheel when the inlet and exhaust valves open and close as the
4. flywheel is rotated slowly.Measure the valves (Tappet) Clearance.
5. Mark the spark ignition timing in case of petrol Engine and fuel injection timing in case
of Diesel Engine.
6. Measure the angles of the various events and plot the valve timing diagram.