Internal combustion engines are very common in our daily lives. Today they range from the cars that most of us drive to the lawn mower that we use to mow the lawn. These engines consume about 30% of the U.S. energy budget, which is about 20% of the world's energy budget. The IC engine that is used in this particular experiment is a four stroke, 1 cylinder engine, with a displacement volume of 77.6ml. The intake and Exhaust valves are placed on the side of the cylinder, in a side or flat-head configuration. When air and fuel or gas goes into an IC engine, the output products are; power, exhaust, and heat.

Yet, the output power differs from the power developed by the gas mixture in the cylinder. This power is called the indicated power. In order to get the indicated power, one needs to find the work done per unit time. And to obtain the work done, the pressure and the gas volume at each instant need to be determined. To measure the exhaust composition, gas detector tubes are used. The heat can be determined by measuring the flow of cooling air and its temperature rise. Power can be calculated using the speed and torque. In this whole experiment, four different speeds were used to obtain different sets of result.

Indicated Power Calculation:

• Make a data sheet including; speed, area inside curve, and whole area.
• Pressure is measured by an optical pressure transducer in the head while crankshaft position is measured using a slotted disc/opto-coupler. This info is fed to a computer where it is scaled, crankshaft to piston position calculated, and plotted.
• Using vissim software, acquire real-time data. Run the engine at speed (1200) and collect a set of data for the gas pressure and gas volume vs time.
• Transfer all data collected into Microsoft Excel and then align each data stream cycle, so that all top dead center positions coincide in time.
• Print out the plot and use a planimeter to measure the area in within the curve of the graph and the whole area including that within and outside the curve.
• Record measurements into the data sheet.
• Use the areas measured to calculate the work.
• Use this equation to calculate the time required for the complete rotation of the camshaft. Time = (2*60)/(1200*1.2)
• Now that you know the work and time just divide the work by the time. This will give the Power.
• Do the same procedures for speeds; 1500, 1800, and 2000. Don't forget to change the speeds when calculating the time.

Power Calculation:

• Make a data sheet consisting of; date, time, room temperature, humidity, pressure, speed, torque, and exhaust temperature.
• Run the engine at four different speeds (1200, 1500, 1800, and 2000)
• For each speed, fill out a data sheet.
• Using the data, solve for omega using this equation. Omega = (speed)*((2*p)/(60))
• Since you know omega, multiply it by the torque to get power

Mechanical Efficiency Calculation:

• The indicated power is greater than the output power. This is so because the power developed by the gas must overcome the internal resistance of the engine (and dyno), namely piston and valve friction and inertia, and belt friction. However the overall mechanical efficiency is the ratio of both powers.

1. Calculate indicated Power
2. Calculate power
3. Calculate mechanical efficiency