THE UNIVERSITY OF NEW SOUTH WALES
School of Mechanical and Manufacturing Engineering
MECH9761 – Automobile Engine Technology
Lab sessions on Week 4 Thu 5 Oct 2023 2-3pm, 3-4pm, 4-5pm
Lab sessions on Week 5 Thu 12 Oct 2023 2-3pm, 3-4pm, 4-5pm
Come to Willis Annexe J18 Room 214A Undergraduate Teaching Lab
• Show up at least 5 mins before your lab session.
• We check attendance with 5% mark given only if the attendance is confirmed.
• Bring this file with you as you will record some data.
• Safety requirements: Wear covered shoes. Tie up your long hair. Store your bag against
the glazed wall.
At the UNSW Engine Research Laboratory, we perform advanced diagnostics to clarify fuel burning
and pollutants formation processes inside the engine cylinder. These findings help engineers design a
next-generation engine that is more efficient and cleaner. To give you a taste of our engine research,
two test rigs (one petrol and one diesel) have been setup. These engines allow the monitoring of
various engine parameters. Please see below specifications of these engines.
Petrol
Bore 70 mm
Stroke 54 mm
Crank Radius 27 mm
Rod Length 84 mm
Displacement Volume 208 cc
Compression Ratio 8.5:1
Diesel
Bore 69 mm
Stroke 62 mm
Crank Radius 31 mm
Rod Length 104 mm
Displacement Volume 232 cc
Compression Ratio 22.0:1
You will assist the demonstrators in operating the engines and adjusting their controls to change the
engine speed and load condition. The engines are mounted to dynamometers and connected to data
acquisition units which allow you to record torque, RPM, in-cylinder pressure, air flow rate and fuel
flow rate.
Operating the petrol engine
1) Open water supply to the test bed.
2) Ensure that there is fuel in the tank and that all taps on the fuel line are open.
3) Set the engine fuel switch to on.
4) Shut the choke on the carburettor. If engine is cold ensure the choke is fully closed, if still
warm then set to half closed.
5) Set throttle and fuel control valve to half-way.
6) Turn on ignition switch.
7) Slowly pull on the start handle until you feel resistance – this is the start of the compression
cycle.
8) Allow handle to return to its original position.
9) Pull the starting handle firmly to start the engine. Repeat steps 6-8 if engine does not start.
10) Allow engine to run for a few minutes in order for it to reach normal operating temperature.
11) Open the choke fully.
12) You are now ready to change the throttle position and dynamometer resistance to simulate
various engine load conditions.
13) Fill out the table below by reading from data acquisition units (explained in a later section).
Engine Speed Torque Power Fuel Flow Rate
Throttle
Choke
Fuel control valve
Operating the diesel engine
1) Open water supply to the test bed
2) Ensure that there is fuel in the tank and that all taps on the fuel line are open.
3) Set engine speed control to half-way
4) Turn on ignition switch
5) Slowly pull on the start handle until you feel resistance – this is the start of the compression
cycle.
6) Allow handle to return to its original position.
7) Pull the starting handle firmly to start the engine. Repeat steps 6-8 if engine does not start.
8) Allow engine to run for a few minutes in order for it to reach normal operating temperature.
9) You are now ready to change the engine speed control and dynamometer resistance to
simulate various engine load conditions.
10) Fill out the table below by reading from data acquisition units (explained in a later section).
Engine Speed Torque Power Fuel Flow Rate
Engine speed control
Data acquisition system
Sensors including engine speed, torque, in-cylinder pressure and air flow rate are connected to the
units pictured below which display the data in real time. Data can then be sent to a laptop for logging.
During the lab exercise you will be involved in zeroing the displays before runs in order to attain valid
readings.
Controlling engine load
The dynamometers mounted to each of the test engines are controlled via water flow rate. Increased
flow rate leads to more load. To adjust the flow rate, simply turn the control valve accordingly. Care
must be taken to ensure that the engine does not run at high speeds for long periods as this will cause
premature failure of the equipment.
Control valve
MECH9761 Laboratory Report Instructions
The following instructions will assist you in processing data files obtained from the engine cycle
analyser software. You are required to complete the provided Matlab code for data processing and
discuss your findings. The report is to be typed up in a word processor and submitted to Turnitin
portal on Moodle by the start of week 8 Demo (Wed 1 Nov 2023 3pm). A formal report styling is
not required; please just complete the following questions.
Task 1 – General Questions
During the laboratory, your demonstrators showed you various engine components.
a) Identify at least three parts that you noticed during the lab.
They made changes to the settings on both the engine and the dynamometer. Answer the following
questions using the explanation given to you during the lab session, as well as consulting lecture notes
and other materials of your choice.
b) What is the purpose of a dynamometer and what performance parameter does it measure?
How were the demonstrators able to change the load on the engine?
c) How was the output of lab engines varied? Does the air/fuel ratio change while doing this?
(Please answer this question separately for SI and CI engines)
d) With the engine-dynamometer setup, is it possible to alter the supplied fuel amount while
maintaining a constant engine speed?
e) For the tested SI engine, its intake manifold has three key components including a choke
valve, throttle body and carburettor. Please explain the role of each of these components
regarding to the engine operation. For example, under what circumstance the component is
used, what factor it controls and in what way it impacts the engine combustion process.
Task 2 – Performance evaluation of the SI engine
Unzip the provided ‘Labdata.zip’ file, open folder ‘Labdata Petrol’. You will find 5 ‘txxx_yyyy.mat’
files, which contain raw in-cylinder pressure data. The ‘xxx’s refer to the torque measured by the
dynamometer (045 = 4.5 Nm, 133 d= 13.3 Nm etc.) and the ‘yyyy’s refer to the engine speed in RPM.
Open one of these files in Matlab and you will see that the CrankAngle parameter ranges from -180 to
+539. These angles are specified in terms of the expansion stroke top dead centre, i.e. -180 to -1 is the
compression stroke, 0 to 179 is the expansion stroke, 180 to 359 is the exhaust stroke and 360 to 539
is the intake stroke. Step by step instruction on data processing using Matlab is as follow.
a) Open Petrol.m in Matlab. Note that on line 12 we are dealing with the 7.2 Nm @ 2410 RPM
case to begin with. Change lines 14 and 55 so that they point to your unzipped Labdata
directory
b) Using ‘CrankAngle’ and other parameters defined in lines 4-10, enter the formula for
combustion chamber volume in line 26.
c) Noting that there is a variable defined as ‘Pressure’ for each case, complete line 31 in order to
obtain PdV.
d) Following the instruction on line 33, complete line 34 to obtain the total work done on the
piston during all 4 engine strokes.
e) Recalling definitions from the lecture notes, complete line 36 to obtain IMEP (in MPa – the
next line will convert it into bar).
f) [Advanced] In lines 41-43, write a loop which will calculate the work done during just the
intake and exhaust strokes (WorkP).
g) [Advanced] From e) and f) complete line 46 to obtain pumping losses (PMEP). Note that this
is work done by the piston on the working fluid, as such, you will need to change the sign to
obtain a positive value. Make sure you put in the necessary conversion in order to get the
answer in bar.
h) Recalling definitions from the lecture notes, complete line 49 to obtain BMEP (in Pa – the
next line will convert it into bar).
i) Frictional losses are the difference between indicated and brake output. Complete line 53 to
obtain FMEP.
j) Run the Matlab code and selected the first data set you would like to process, create P-V
(Pressure-Volume) plots for the case. The code will automatically save the processed data
in the same folder.
k) Complete the same processes for the 4 other engine operating conditions. Ensure that you
change lines 14 and 55 to correct file names each time so that you don’t overwrite your
previous work. Display all P-V plots in your report document.
l) In your report document, complete the following table:

m) Use the P-V diagrams and the data calculated, discuss the effect of Torque and RPM on
PMEP and FMEP, and provide reasons respectively (If possible, refer your answer to the
P-V plots you showed previously).
n) Calculate the mechanical efficiency for each case, find which operating condition has the
highest mechanical efficiency and discuss why this is the case (Hint: Mechanical efficiency
can be thought of as the ratio between gross indicated output and brake output. Gross IMEP,
net IMEP and PMEP are related via the following formula: Gross IMEP = PMEP + net
IMEP).
Task 3 – Performance evaluation of the CI engine
Open the folder ‘Labdata Diesel’. You will find 2 ‘_load_diesel.mat’ files for raw in-cylinder pressure
data for high and low engine operating conditions, and 2 ‘m’ files for data reduction and plotting. In
the ‘Diesel.m’ file, geometric information of the diesel engine and operating conditions are provided.
You need to complete this code similar to that for petrol engine to obtain data for in-cylinder pressure
plot, IMEP calculation, and apparent heat release rate plot.
a) Load one of the “_load_diesel.mat” file by using ‘load’ function in the Matlab. Follow the
same procedure as for the petrol engine case and copy formulas up to line 35 to calculate the
IMEP.
b) Assuming a constant specific heat ratio of 1.35, we want to apply the first law of
thermodynamics and calculate apparent heat release rate. Since we’ve already obtained
Pressure(x), dV(x), Volume(x), and dP(x), we can complete line 50 for aHRR at a given
crank angle.
c) Execute the code and you will notice that 1 ‘mat’ file is created in the current folder. In line
61, we used a save function to record ‘CrankAngle’, ‘Pressure’, “HRR_filt”, and ‘IMEP’ for
further analysis.
d) Execute the ‘plotter.m’ in Matlab. This will draw two figures: in-cylinder pressure over crank
angle with notes for IMEP values and apparent heat release rate versus crank angle.
Following the instruction given in line 10 and 11, plot the other case and complete the
incylinder pressure viewgraph.
e) Discuss the effect of fuel quantity on the in-cylinder pressure traces and its impact on IMEP.
f) In the plotter.m file, follow the instruction in line 28~29 to plot apparent heat release rate
traces.
g) Discuss the effect of fuel quantity on the heat release rate traces.
Torque
(Nm) RPM
IMEP
(bar)
PMEP
(bar)
BMEP
(bar)
FMEP
(bar)
4.5 2100
7.2 2410
8 2170
13.3 2425
13.3 2550