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College of Engineering and Physical Sciences
School of Mechanical Engineering
Powertrain Engineering Project
Group 7
Group Members
First Name Last Name ID Number
Enzo Cavaliero 871854
Matthew Florida-James 858410
David Horsley 937926
Hatef Khadivinassab 1128017
Sina Khonsari 1128019
Mehrdad Silatani 1128044
Ben Sykes 950208
Jonathan Telford 858543
Table of Contents Project 1 – Engine ................................................................................................................................... 1
1. Introduction ........................................................................................................................................ 1
1.1 Engine Benchmark ........................................................................................................................ 1
2. Review of Advanced Engine Techniques ............................................................................................. 3
3. Target Engine ...................................................................................................................................... 4
4. Design Target of the Engine Specification .......................................................................................... 5
5. Basic Engine Design Parameters ......................................................................................................... 6
5.1 Mean Effective Pressure Parameters in Different Conditions ...................................................... 9
6. Engine Operating Dynamic Load Flow and Speed Diagrams .............................................................. 9
7. Engine Balance and Flywheel ............................................................................................................ 11
7.1 Mass Distribution in the Crankshaft ........................................................................................... 11
7.2 Engine Torque Fluctuation Curves .............................................................................................. 12
7.3 Flywheel Design .......................................................................................................................... 13
8. Piston and Conrod Design ................................................................................................................. 14
9. Valve Train Design ............................................................................................................................. 16
9.1 Requirements .............................................................................................................................. 16
9.2 Arrangement ............................................................................................................................... 16
9.3 Valve Timing ................................................................................................................................ 17
9.4 Valve Timing Maps ...................................................................................................................... 17
9.4.1 Idling ..................................................................................................................................... 18
9.4.2 Maximum Torque ................................................................................................................. 18
9.4.3 Maximum Power .................................................................................................................. 18
Project 2 – Driveline and Transmission ................................................................................................. 19
1. Benchmarking the Current Driveline ................................................................................................ 19
2. Performance Analysis ........................................................................................................................ 21
3. Review of Advanced Transmission Technologies ............................................................................. 22
4. Main Design Parameters ................................................................................................................... 25
5. Powerflow through the Driveline ..................................................................................................... 27
6. Vehicle-Powertrain Simulation ......................................................................................................... 28
References ............................................................................................................................................ 32
Page | 1
Project 1 – Engine
1. Introduction Since its introduction in 1970, the Range Rover has always been known as one of the most reliable luxury 4x4
vehicles. It was the first car which was successfully able to balance luxury and comfort with performance and
durability. Since the beginning of the 21st century, the performance of SUV’s has improved significantly, such
that they now rival the performance of saloon cars. Production of models such as the Porsche Cayenne, Audi
Q7, BMW X5 and X6 are good examples of this evolution. In 2005, the Jaguar Land Rover group introduced a
new model to the Range Rover class as a response to its rivals. The Range Rover Sport combines the ability and
performance of its predecessors with an innovative and sleek design image.
1.1 Engine Benchmark
The Range Rover Sport model which is to be benchmarked and analysed uses a 4.2 litre V8 supercharged
engine. This engine was used in the previous generation of the Range Rover Sport which was replaced by a 5.0
litre V8 engine with Land Rover’s 6th generation supercharger. In fact the 2010 model is the perfect model to
base the upgrade of our engine on since the 2010 model has been upgraded in aspects such as power, torque,
fuel consumption and CO2 emissions compared with the 2009 edition.
Model 2009 2010
Engine Type Supercharged V8 Supercharged V8
Capacity 4.2 Litre 5.0 Litre
Compression Ratio 9.1:1 9.5:1
Power 385 BHP at 5750 RPM 510 BHP at 6000 RPM
Torque 550 Nm at 3500 RPM 624 Nm at 2500 RPM
Fuel Consumption (combined) 17.8 mpg 19.0 mpg
CO2 Emissions 374 gr/km 348 gr/km
0-60 mph 7.2 Seconds 5.9 Seconds
Table 1: Comparison of the latest Range Rover Sport supercharged models
Figure 1: 2009 Range Rover Sport 4.2 Litre
Figure 2: 2010 Range Rover Sport 5.0 Litre
Page | 2
Brand and
Model
2010 BMW X6 2010 Toyota
Land Cruiser
2009 Porsche
Cayenne turbo
2010 Audi Q7
Engine Type Twin Turbo V8 V8 Gasoline Turbo Charged
V8
V8 TDI
Capacity 4.4 Litre VVTi 4.7 Litre 4.8 Litre 4.2 Litre
Compression
Ratio
9.3:1 10.0:1 10.5:1 12.5:1
Power 555 BHP 284 BHP 550 BHP 272 BHP
Torque 677 Nm 445 Nm 750 Nm 760 Nm
Fuel
Consumption
(combined)
20.3 mpg 16.33 mpg 19.0 mpg 28.5 mpg
CO2 Emissions 325 gr/km 340 gr/km 358 gr/km 262 gr/km
0-60 mph 4.7 Seconds 9.5 Seconds 4.9 Seconds 6.4 Seconds
It should also be mentioned that the 4.4 litre V8 Range Rover Sport is not an appropriate comparison for the
discussed model since it is a naturally aspirated engine and has no boosting system.
It can be seen that the Range Rover Sport engine has major weaknesses when it comes to environmental
factors such as fuel consumption and CO2 emissions. In fact, even the upgraded model still poses problems due
to its considerable environmental impact. This issue consequently results in higher tax charges, for example,
the daily London congestion charge for the Range Rover Sport is £10 per day.
In conclusion, the Range Rover Sport has the following strengths and weakenesses:
Strengths:
Powerful engine
High torque available at low engine speed which makes it ideal for off-road use
Good acceleration (0-60 in 7.1 seconds)
Weaknesses:
Poor fuel consumption
High CO2 emissions
Table 2: Comparison of Range Rover’s main competitors in the market
Page | 3
2. Review of Advanced Engine Techniques Since the first car was invented, engineers have tried to optimise the engine to generate improved power and
torque. Lately, environmentalists pose issues regarding the emissions of automobiles, which is a direct result
of how the combustion takes place in the engine. Consequently, engineers and scientists are challenged with
minimising the emitted gases and particles as well as maximising the torque and power. Another problem that
every car manufacturer is faced with is the amount of fuel consumed per mile travelled. This concern was not
manifested until the 1973 oil crisis where almost all automotive companies realized that they could not rely on
oil products being accessible for limitless generations. Car engine manufacturers must pass through all these
difficult stages to be able to manufacture the optimum engine. Nowadays, one can observe the cutting edge
technology implemented in automobile engines in bi-fuel engines using both biofuel and oil-based fuels.
Hybrid engines use both electric power and gasoline in complex valve-train arrangements such as variable
valve timing (VVT) and continuous variable valve lift (CVVL) to super or turbo charger engines.
The Split-injection concept is the advanced form of bi-fuel and flexible fuel engines. In split-injection engines
it is possible to blend two or more fuels in the cylinder at any desired ratio [1]. The biofuel can be injected
utilizing the direct injection method (DI) and oil-based fuel can be injected using the port fuel injection method
(PFI) [1]. These types of engines combine the advantages of PFI and DI methods to minimize the particulate
matter emissions and resolving the cold start issues whilst maintaining the same performance of the engine
using the cross-over theory to control the in-cylinder mixture ratio [1].
VVT or variable valve timing is a powerful method for optimizing the torque, power and fuel consumption
rate [2]. The principle is based on the combination of two or more different valve overlaps at different engine
speeds. If the engine speed becomes high, greater valve overlaps could be used. However, in lower RPMs high
valve overlap results in an unacceptable emission rate.
BMW X6M 4.4L V8 Porsche Cayenne Turbo S (4.8L) VW Touareg 4.2L TDI
Figure 3: BMW, Porsche and Volkswagen Cars and Engines
Page | 4
Continuous variable valve lift technology, which was first developed by Honda (VTEC), has been targeted to
enhance the power of engine at high engine speeds by supplying more air as well as reducing emitted gases at
lower revolutions by improving the fuel-air mixture. The most innovative of these technologies is Valvematic
by Toyota, which has almost no disadvantages [3]. The result is lower emissions and greater engine power.
The idea of a supercharged engine was first introduced in 1860 in the United States and developed in
Germany in 1885 in order to be utilised in internal combustion engines [4]. Turbochargers, which can be fitted
in the category of superchargers, were developed in 1905 in Switzerland [5]. Turbochargers and Superchargers
are forced Induction systems to improve the efficiency of internal combustion engines. They both work on the
concept of compressing air; hence, injecting more air molecules into the engine's combustion chambers.
Nevertheless, the main difference of these two boosting mechanisms is how they get their drive power. The
Supercharger’s main shaft is connected to the engine flywheel and takes its power from the engine output
shaft. However, the turbocharger absorbs its drive power from exhaust gases.
Overall, there are numerous innovative technologies to optimize the engine characteristics. Subsequently,
Dual-injection, CVVL and a more advanced supercharger are to be used in optimisation of the AJ34S engine.
3. Target Engine Having compared the competitors’ engines and the latest 5.0-litre engine of the range rover sport, it was
decided to increase the engine to a 4.4 litre capacity. The reason for this selection was that the majority of
competitors are using engines with higher capacity, while the latest range rover with the 5.0 litre supercharged
engine produces acceptable power and torque, it still suffers from having high emissions as well as a high fuel
consumption rate.
To solve the environmental issues related to such engines it was decided to add Valvematic technology to
overcome fractions of this weakness. Valvematic is an innovative development of Toyota’s proven dual VVTi
technology. In addition to the variable valve timing of the inlet and outlet valves, Valvematic adds a system
that continuously varies the lift of the inlet valves. This allows better control of the inlet flow volume and
speed, providing a break-through in combustion efficiency that delivers more power and fewer emissions. As
the volume of the air and fuel entering the cylinder is controlled by this CVVL technique, the throttle valve can
be held open when the engine is running. This minimises the flow restrictions to maximise airflow efficiency
into the inlet manifold [6].
It must be noted that the concept of SUV cars mainly focuses on the ability of vehicles to perform in various
road conditions as well as offering a fast but comfortable ride. Furthermore, it has never been known as an
economical and environmental-friendly class. Therefore, it should not be expected to achieve greatly improved
results when it comes to CO2 emissions and fuel consumption rate. By this reasoning, the concept of dual-
injection technology with gasoline PFI and bio-ethanol DI was applied to decrease the CO2, NOx and HC
emissions whilst increasing or at least maintaining the same power. [1] found that the indicated mean
effective pressure (IMEP) increases with increasing the direct injection of bioethanol. This occurs when the
blend ratio of biofuel DI to gasoline PFI is reduced from 85 to 15[1]. Due to the fact that the increase in IMEP
results in higher mechanical efficiency [7], an improvement in brake horsepower (BHP) is expected after
implementing this method.
Page | 5
4. Design Target of the Engine Specification
The maximum torque of the updated
model is 600Nm occurring at 2800-
3800rpm compared to the old model
which is 555Nm occurring at 3200-
3800rpm. The maximum power of the
updated model is 432.53bhp at an
engine speed of 5600rpm compared to
the old model which is 390bhp at
5750rpm.
Original Engine Target Engine
Capacity (CC) 4200 4400
Number of Cylinders 8 8
Engine Layout V type V type
Supercharged YES YES
Fuel type Gasoline DI Dual fuel (bio-ethanol DI and gasoline PFI)
Maximum Power 390 BHP at 5750 RPM 440 BHP at 5200 RPM
Maximum Torque 550 Nm 600 Nm
CO2 Emissions (gr/km) 374 Below 300
Fuel Consumption (MPG) 17.8 Over 20
Stroke (mm) 90.3 90.3
Bore (mm) 86 88.06
Compression Ratio 9.1:1 11.5:1
Figure 5: Power vs. Different Engine Speeds for the
4.2L and 4.4L Engines
Figure 4: Torque vs. Different Engine Speeds for the 4.2L
and 4.4L Engines
Page | 6
5. Basic Engine Design Parameters Many improvements have been inspired by the new 2011 5.0 litre model’s engine. The new engine is a
benchmark in its class and is a considerable improvement in comparison to its predecessors. The
improvements are listed below:
Using centre mounted spray guided fuel injection with several holes which results in high pressure
injection right to the centre of every cylinder and consequently better mixture with air.
Implementing various fuel injection plans to make the engine heat up faster after start which will
result in better CO2 emissions
The supercharger is upgraded to the latest 6th generation TVS (Twin Vortex System) with its own
double water used inter coolers. A minor change to the helix rotor design enhances thermal
efficiency.
Torque and power is also optimized by a variable inlet manifold which changes the length of its eight
inlet tracts. The manifold opens up more widely (at about 650 mm) to increase torque at low speeds
and tightens up (to about 320mm) at high speeds to release more power.
To improve heat transfer from engine, oil to Water heat exchanger has been used which again aids
the engine in warming up more quickly after first ignition.
To prevent frictional efficiency losses, DLC (Diamond like Carbon) coating is accurately used on some
of the effective components.
Below are the basic engine design parameters at idling, maximum torque and maximum power.
Idling
0
10
20
30
40
50
60
0.000 100.000 200.000 300.000 400.000 500.000 600.000
P (
bar
)
V (cc)
P-V diagram
Intake
Compression
Combustion
Exhaust
Figure 6: In-Cylinder
Pressure versus
Swept Volume for
Engine
Page | 7
Maximum Torque
0
10
20
30
40
50
60
0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000
P (
bar
)
Theta (rad)
P-Theta diagram
0
10
20
30
40
50
60
70
80
0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000
P (
bar
)
Theta (rad)
P-Theta diagram
0
10
20
30
40
50
60
70
80
0.000 100.000 200.000 300.000 400.000 500.000 600.000
P (
bar
)
V (cc)
P-V diagram
Intake
Compression
Combustion
Exhaust
Figure 8: In-
Cylinder Pressure
versus Swept
Volume for Engine
Figure 9: In-
Cylinder Pressure
versus Crank Angle
Figure 7: In-
Cylinder Pressure
versus Crank Angle
Page | 8
Maximum Power
0
10
20
30
40
50
60
70
80
90
0.000 100.000 200.000 300.000 400.000 500.000 600.000
P (
bar
)
V (cc)
P-V diagram
Intake
Compression
Combustion
Exhaust
0
10
20
30
40
50
60
70
80
90
0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000
P (
bar
)
Theta (rad)
P-Theta diagram
Figure 11: In-
Cylinder Pressure
versus Crank Angle
Figure 10: In-
Cylinder Pressure
versus Swept
Volume for Engine
Page | 9
5.1 Mean Effective Pressure Parameters in Different Conditions
6. Engine Operating Dynamic Load Flow and Speed Diagrams At Idling:
Idling Maximum Torque Maximum Power
IMEP (bar) Intake
Energy (J) IMEP (bar)
Intake Energy (J)
IMEP (bar) Intake
Energy (J)
4.91 58.14 23.15 82.27 45.18 93.04
GMEP (bar) Compression
Energy (J)
GMEP (bar)
Compression Energy (J)
GMEP (bar)
Compression Energy (J)
1.13 -222.51 5.33 -403.46 10.41 -634.37
BMEP (bar) Combustion
Energy (J) BMEP (bar)
Combustion Energy (J)
BMEP (bar) Combustion
Energy (J)
4.28 1004.44 17.12 1434.13 15.69 1647.68
FMEP (bar) Exhaust
Energy (J) FMEP (bar)
Exhaust Energy (J)
FMEP (bar) Exhaust
Energy (J)
0.63 -132.95 6.03 -275.51 29.49 -487.22
mechanical efficiency
Total Energy (J)
mechanical efficiency
Total Energy (J)
mechanical efficiency
Total Energy (J)
87% 707.12 74% 837.42 35% 619.12
Figure 12: Force
versus Crank Angle
Maximum Gas Force = 31300N at 382o
Minimum Inertial Force = -800N at 360o
Table 4: Engine Performance Simulation in Various Conditions
Page | 10
At Maximum Torque:
At Maximum Power
Figure 14: Force
versus Crank Angle
Maximum Gas Force = 45000N at 382o
Minimum Inertial Force = -7500N at 360o
Maximum Gas Force = 51500N at 382o
Minimum Inertial Force = -20000N at 360o
Figure 13: Force
versus Crank Angle
Page | 11
Figure 15: Numbered
Cylinder Arrangement of
the Engine
Figure 16: Firing Order
Figure 17: Centre Distances of Mass For
Crank Web
7. Engine Balance and Flywheel
7.1 Mass Distribution in the Crankshaft
V8 engines can achieve complete balance by 2 shaft balancers for the first order force. The eight cylinder
engine is similar length to that of a straight fur cylinder engine. Therefore the crankshafts will be of similar
length. First the firing order of the engine must be determined. Figure 15 shows the
numbered cylinder arrangement of the engine. The firing order is 1-3-7-2-6-5-4-8. The
engine rotates in the clockwise direction and takes two crankshaft rotations, or through
a crank angle of 720°, to complete its firing sequence.
A cross-plane crankshaft will be used in the engine.
This allows a power stroke from the engine every 90° of
rotation of the crankshaft. Although it is the most
common crankshaft type in modern vehicles, the
counter weights on the crankshaft are heavy. This
results in an engine that will offer a slightly slower
response due to the rotating inertia of the crank
shaft. The advantage of using a cross-plane crank shaft is that it achieves good
balance. This reduces the need for balancing shafts within the engine, saving
engine power and overall weight.
The crankshaft counter weights decreased in size and weight as you move from the outside of the crank,
towards the centre of the crankshaft. This is because the inner cylinders partly balance themselves. The two
weights at the ends of the crankshaft are quite large as they have to counter act the forces applied to the
crankshaft by two cylinders alone. V8 engines can achieve complete balance by shaft balancers for the first
order force. No second order force is present due to the cross-plane
crankshaft configuration.
Web balancers are added to the crank shaft to counter act the rotating
combined mass of the two piston, con-rod and crank pins.
1
2
3
4 8
7
6
5
1, 6
3, 5
7, 4
2, 8
Page | 12
7.2 Engine Torque Fluctuation Curves
At Idling:
At Maximum Torque:
Figure 18: Torque
Fluctuation versus Crank
Angle
Figure 19: Torque
Fluctuation versus Crank
Angle
Page | 13
At Maximum Power:
7.3 Flywheel Design
Table 5: Flywheel
Characteristics
Figure 20: Torque
Fluctuation versus Crank
Angle
Figure 21: Flywheel Design
Page | 14
8. Piston and Conrod Design The first step we took to design our piston and conrod was to work out the conrod length. We took the length
of the conrod from the 2005 Range Rover Sport, and used this in the equation with our new stroke height:
Where: r = stroke length/2 and l = Conrod height
Our stroke height is 90.4mm, and the Conrod length is 150.67mm [8]. So = 0.30mm (2.d.p)
The lower limit for is usually 1/3 and can be no lower than ¼ [9]. We have decided to use the length of
=0.3 because it is still above the critical value of a 1/4.
The next step was to make sure that we can use our new bore size with the dimensions that currently exist.
We took the dimensions of the 2005 Range Rover sport Piston, and updated our new bore size (mm): D =
88.06, H = 64.5, H1 = 32.3, H2 = 48, H3 = 15.8, h = 6, d = 23.5 [8]. From the equations below we can see that
these dimensions are well inside the limits, so these are acceptable to use as the dimensions for our piston.
Our engine - dimensions in (mm)
H1/D = 32.3 / 88.06 = 0.37
H/D = 64.5 / 88.06 = 0.73
H2/D = 48 / 88.06 = 0.55
h/D = 6 / 88.06 = 0.068
d/D = 23.5 / 88.06 = 0.27
Now we have the dimensions, we can produce engineering drawings of the parts.
Figure 22: Limits of acceptable main dimensions for a petrol engine (mm) [9]
Page | 15
150.67
Figure 23: Piston and Conrod assembly with dimensions (mm) Figure 24:Conrod design with dimensions (mm)
Page | 16
Our engine is going to be dual fuel, with a direct injection ethanol sprayer nozzle facing vertically down from
the top centre of our cylinder. Usually in cars with a vertical sprayer nozzle, like diesels, the force of the spray
is high and each spray of diesel would hit the piston crown. This means the crown would need to be designed
with a bowl design of some sort, so the spray can be directed back up around the cylinder to create swirl.
As our engine is dual fuel, the sprayer nozzles are required to inject far less volume of fluid than that of a
normal diesel nozzle. This means that the spray will not reach the piston and will not need to be directed back
around the cylinder for swirl. For this reason, we have designed our piston to have a simple flat crown.
9. Valve Train Design
9.1 Requirements
The valve-train requirements are as follows [10]:
To provide maximum volumetric efficiency
Prompt and swift opening and closing of the valves
Maximum flow area
Minimum noise, vibration and harshness
Minimum number of components
Minimum weight
Minimum friction losses
Reliable and durable
9.2 Arrangement
We must also consider the arrangement of our valve-train. Our vehicle uses a double overhead camshaft arrangement which is suitable for high speed operation and also more flexible in terms of its positioning. It is
Figure 25: Piston design
Flat crown design
Page | 17
operated by two camshafts within the cylinder head, one operating the intake valves and the other operating the exhaust valves.
We must also determine the number of valves per cylinder. Our improved engine would use 4 valves per cylinder. This arrangement has many advantages:
Lighter valves which will have smaller lift
Smaller valve diameter and a lower valve temperature
Better fuel consumption
Better performance
The disadvantages of this arrangement over the simple 2 valves per cylinder system are that it is more expensive and has increased friction losses.
The last thing to consider is the type of valve train drive to be used. Our engine will use a chain drive rather than a belt drive. A chain drive can take a higher load and is relatively durable. The determining decision factor in using a chain drive is that it is more reliable than a belt drive. However, it is more complex and more expensive.
9.3 Valve Timing
The cam specifications and valve timings are very important for maximising engine output, at the correct
times in the engine’s cycle. The opening and closing of the inlet and exhaust valves at the correct time in
relation to the piston position must be precisely controlled, either at a fixed compromise position, or variable
within finely controlled limits. Using Variable Valve Timing (VVT), we can alter the amount of valve overlap;
this is the time when both valves are open at the same time. Smaller overlap gives smooth running of the
engine, more torque at slow speeds but at high speed it has poor performance. With a larger overlap, the high
speed performance is superior due to better engine breathing. However, at low speeds, large overlap causes
poor performance, rough idling and higher exhausts emissions. Engines using VVT and variable valve lift can
operate efficiently at a wider range of speeds and deliver better performance at high speeds. Whereas,
engines with fixed valve timing can only operate most efficiently at one speed.
To improve our engine, we needed to increase performance but at the same time decrease engine emissions.
To obtain the best engine performance, we need the following criteria:
An early enough intake opening to allow enough air in
A delayed intake closing to allow a long enough opening period to maximise the charge quantity
An advanced exhaust opening to let burned gas out early to reduce pumping loss
A delayed exhaust closing to minimise residual burned gas
At the same time we also want to reduce engine emissions. For this to occur, we need:
A reduced advance in intake opening to prevent short-cut from intake to exhaust port
A reduced delay in intake closing to prevent back flow into the intake port
A reduced advance exhaust opening to allow more complete combustion
A reduced delay in exhaust closing to increase exhaust gas recirculation
9.4 Valve Timing Maps
TDC = Top Dead Centre IO = Intake Opening BDC = Bottom Dead Centre IC = Intake Closing ATDC = After Top Dead Centre EO = Exhaust Opening BBDC = Before Bottom Dead Centre EC = Exhaust Closing
Page | 18
9.4.1 Idling
Intake Opening – 14⁰ TDC
Intake Closing – 25⁰ ABDC
Exhaust Opening – 29⁰ BBDC
Exhaust Closing – 6⁰ ATDC
9.4.2 Maximum Torque
Intake Opening – 15.7⁰ BTDC
Intake Closing – 19⁰ ABDC
Exhaust Opening – 11.5⁰ BBDC
Exhaust Closing – 10.4⁰ ATDC
9.4.3 Maximum Power
Intake Opening – 11.1⁰ BTDC
Intake Closing – 20.5⁰ ABDC
Exhaust Opening – 21⁰ BBDC
Exhaust Closing – 7.7⁰ ATDC
Figure 26: Valve Timing Map
at Idling
Figure 27: Valve Timing Map
at Maximum Torque
Figure 28: Valve Timing Map
at Maximum Power
Page | 19
Project 2 – Driveline and Transmission
1. Benchmarking the Current Driveline The Range Rover Sport 4.2 Litre Supercharged uses a 6-speed automatic gearbox with CommandShift and
adaptive mapping, which is manufactured by [11]. An electronically self-locking differential has been used with
the option of rear differential lock. The exact model name is “ZF 6HP26” and the gear ratios are as follows:
1st High 4.17:1
Low 12.22:1
2nd High 2.34:1
Low 6.86:1
3rd High 1.52:1
Low 4.46:1
4th High 1.14:1
Low 3.35:1
5th High 0.87:1
Low 2.54:1
6th High 0.69:1
Low 2.03:1
Reverse High 3.40:1
Low 9.97:1
Final Drive Ratio 3.54:1
The Range Rover Sport 4.2 litre supercharged can accelerate from 0 to
60 MPH in 7.2 seconds with this driveline.
The latest improved version of the Range Rover Sport again uses a 6
speed automatic gearbox but with the ability to change gears from
behind the steering wheel. It is called the 6HP28 and is also made by the
German manufacturer ZF. This is the upgraded version of the second
generation of the previously used 6HP26.
Both ZF 6HP26 and 6HP28 have gears shift times below a human’s limit of perception (a few milliseconds),
yet the 6HP28 is 50% faster in gear changing times in comparison to 6HP26. The second generation utilises the
“Lepelletier” gear set which decreases the number of components whilst improving the efficiency of the
gearbox. The mentioned improvement along with the substitution of the plastic oil pan as a replacement for
High
Transfer
Ratio 1.00:1
Low
Transfer
Ratio
2.93:1
Figure 29: HP 28 Drivelive
Table 6: Current Transmission Ratios
Page | 20
the metal one on the bottom of the gearbox results in a less weighty gear set. This feature along with better
communication between the Engine Control Unit (ECU) and the Transmission Control Unit (TCU) and several
minor improvements results in 3% better fuel consumption.
Summary of the Comparison:
6HP28 (Second Generation)
Compared to 6HP26 (First
Generation)
Fuel Consumption Improved by 3%
Throttle Response Improved by 50%
The table below shows a breakdown of the second generation of ZF six-speed automatic
transmission [12].
Input Torque(max) 700 Nm
Ratio Spread 6.04
Acceleration Values Improved acceleration by reduced response times
and optimized torque converter designs
Reduction in Response Times Up to 50%
Fuel Consumption Savings 3 % (gasoline), 6% (diesel)
Neutral Idle Control (NIC) Decoupling of the converter at standstill which leads
to a reduction in fuel consumption
Cooling Oil Volume Control Increase of cooling oil through-flow e.g. up to 50%
(from 10 to 15 l/min)
Table 7: Summary of Transmission Comparison
Table 8: 6HP28 Features
Page | 21
2. Performance Analysis Of the rival manufacturers, BMW uses an 8 speed automatic transmission on the X6 M, and Porsche uses a 6
speed tiptronic S on the Cayenne.
The table below lists the driveline comparisons from other competitive vehicles in the class:
Model 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear Reverse
Gear
Final Drive Axle Ratio
Porsche Cayenne S
4.8L 4.15/1 2.37/1 1.56/1 1.16/1 0.86/1 0.69/1 3.39/1 3.27/1
Volvo XC90 4.4L
4.15/1 2.37/1 1.56/1 1.16/1 0.86/1 0.67/1 N/A 3.33/1
BMW X5/X6 4.4L
3.57/1 2.20/1 1.51/1 1.00/1 0.80/1 N/A 4.10/1 3.64/1
Range Rover
Sport 5.0L 4.17/1 2.34/1 1.52/1 1.14/1 0.87/1 0.69/1 3.40/1 3.54/1
Range Rover Sport
(2005-2009) 4.2L
4.17/1 2.34/1 1.52/1 1.14/1 0.87/1 0.69/1 3.40/1 3.54/1
After comparing the main leaders in the SUV class along with the latest version of the Range Rover Sport, it
was decided to upgrade the gearbox system to ZF 6HP28 which is used in the 2011 Range Rover Sport. The
benefits to this change are:
Improved gear shift quality in terms of time and smoothness which leads to better acceleration
Reduced weight of the gearbox resulting in better performance and fewer emissions
The ZF 6HP28 has good compatibility with the Range Rover’s current engine
Paddle shifters are installed behind the steering wheel
Table 9: Driveline Competitor Comparisons
Page | 22
3. Review of Advanced Transmission Technologies New and improved methods of automotive transmissions are always under development. This is to increase
performance, ease of use, efficiency and reliability not only for the transmission but for the whole vehicle.
With the increasing power output of engines, the transmission systems have to be designed to handle greater
amounts of power while becoming more compact in size.
Direct-Shift Gearbox
The direct shift gear box, or DSG, is traditionally a transaxial type gearbox. The gear box features two
clutches, each driving a set of gears. For example, the outer clutch will be driving gears 1, 3 and 5, where the
inner clutch pack will be driving gears 2, 4 and 6. The clutches are electronically controlled which can give the
driver full or semi-automatic transmission.
With the use of two clutches, the DSG can achieve faster shift
times than any other type of automotive transmission [13]. The
electronically controlled clutch eliminates the requirement for a
torque converter as required by a traditional automatic
transmission. Due to the elimination of the torque converter,
higher efficiencies can be achieved due to reduced loss of
torque. DSG also provides no loss of torque transmission from
the engine to the driving wheels during gear shifts.
An attractive feature of the DSG is the manual semi-automatic
control of the transmission. Manual control however can only
achieve shifting in a sequential pattern. This is due to the order
sequence of gears being on different clutches in the gearbox.
Up to 15% higher fuel economy can be achieved by using a DSG
when compared to traditional automatic transmissions.
The two clutches are concentric with each other, with the shaft for inner clutch hollow, allowing the solid
shaft to pass through and make connection with the outer clutch. In theory, due to the outer clutch being
significantly larger, it can handle more torque. Due to space constraints, it is common to find DSG
transmissions with multi-plate clutches rather than a single large
plate clutch.
Manumatic Transmission
Manumatic transmissions allow the driver control of gear
selection within an automatic gear box. Manumatic systems
enhance the control of the transmission, usually by steering
column paddle shifts or a modified gear shifter.
This type of transmission utilises a fluid torque converter to
transmit the torque from the engine to the gear box [3]. This
offers consistently smooth gear shifts between gears, a
desirable characteristic in high end luxury vehicles. Due to
the fluid torque converter however, manumatic
transmissions are not favoured in high performance
applications.
Figure 30: A 6-speed DSG Transmission [14]
Figure 31: Automatic Gearbox with Manumatic Control (Showing Torque Converter) [16]
Page | 23
Manumatic transmission offers the driver manual gear selection or a fully automatic mode where the gears
are changed electronically. This is largely dependent on engine speed and throttle position. Many automotive
manufacturers currently use manumatic transmissions in their vehicles and it is known as variety trade names
such as “Tiptronic” for Porsche and “iShift” for Honda [15].
Continuously Variable Transmission – CVT
CVT is a type of automated transmission used in some road cars. It provides more efficient power, better fuel
economy, and smoother gear changes than traditional automatic gear boxes. It works in a totally different way
to most gear boxes, in that instead of having a fixed number of gear ratios that the driver or CPU has to pick, it
has an infinite amount of ratios available due to the design. Most CVT’s use two cone shaped pulleys facing in
opposite directions, with a chain or belt wrapped around them both. One pulley is attached to the engine
(Input), and one to the driving wheels (Output). By moving one or both pulleys, you can change the gear ratio
seamlessly from very high all the way through to very low. It works in the same way that a bicycle chain does:
If you move the input pulley outwards so that the chain is on the small end of the cone, and the output pulley
inwards so that the chain is running on the large end of the cone, you will get a low ratio (large number of
engine revs produces a low number of wheel revs and vice versa) [17].
As the CVT can constantly vary the engine speed and the engine
revolutions, it can pick the exact torque and revolutions per minute to
not only achieve better acceleration, but also better fuel economy.
The biggest problem with CVT is that people are averse to changing
their opinion on unknown technology. As the power is applied more
smoothly and the engine can rev at various speeds throughout the
acceleration, cars that have a CVT sound and react very differently
from a conventional transmission. When people drive a car with CVT
they think it is slower than a normal automatic, even though it would
more than likely accelerate more quickly. The sounds of revving at
different speeds have also caused people to think the gearbox is on the
verge of breaking [18].
Dual Clutch Transmission (DCT)
Dual clutch transmission is a mix between a manual and an automatic transmission. It is similar to manual in
that it has input and output shafts to mount the gears, synchronizers to reduce grinding, and a clutch. It is also
similar to an automatic, in that, the computer in the car engages
and disengages the clutch instead of the user. The DCT was an
upgrade from former Semi Manual Transmissions (SMT) which had
lag in gear shifts.
Where the DCT is superior is in its unique design. As the name
suggests, the DCT has 2 clutches. One gear shaft is hollow, and the
other is located inside the other one. One controls the even gears
(2,4,6,R), and the other controls the odd gears (1,3,5) [20]. So
when the 1st gear is engaged, the second clutch can be ready to
take over meaning that the gear changes are a lot quicker and a
lot smoother than standard manual transmissions. This
improvement in speed and quality of the changes means a huge
improvement in performance of the vehicle, and an
improvement in fuel economy, which is why this technology is
being implemented by most big name car manufacturers in the
market currently.
Figure 32: Cone design CVT
transmission from a Lexus [19]
Figure 33: Basic layout of a DCT
transmission [20]
Page | 24
One disadvantage of the DCT is that the engine has to be modified to fit the new technology in, which would
mean a high initial cost for the first cars fitted with it. This deters potential buyers.
Zeroshift Transmission
Zeroshift is a type of automated manual transmission (AMT), just like DCT, but with seamless shifts between
gears. This innovative new idea has been invented and developed by a man from New Zealand and is now set
to take over the transmission market, and is being considered by all the major car brands for their 2011 car
designs. Zeroshift claims to be the fastest AMT on the market, but also the smoothest, the best accelerating,
and the most fuel economic [21]. It is lighter, cheaper, and most conveniently of all, it just replaces the
synchromesh in manual and automatic gearboxes, so most cars will not have to be developed too much to be
able to fit it in. It manages all this with its simple yet innovative
design:
There are 1 pair of drive rings between each gear, and each pair has
3 pairs of ‘bullets’ on them, so 3 on 1 ring, and 3 on the other. Each
drive ring is double sided, it can drive with one side, so in one
direction, and eliminate backlash with the other side. When the 1st
ring moves across to engage the 1st gear and start driving it with the
bullets, the 2nd ring will move across to take away the backlash. Once
the backlash has gone, the second ring will move across to the 2nd
gear and engage it. This means that effectively 2 gears are driving
simultaneously for less than a microsecond until the torque of the
second gear exceeds the 1st and will take over driving the shaft. Then
the 1st ring disengages from the 1st gear and moves over to the 2nd
gear to take up the backlash. This happens again and again throughout the gear set, meaning that each
changeover is seamless and the torque of the engine is never interrupted from its transfer to the wheels [22].
Zeroshift can improve fuel economy by an average of 5% in a manual and 15% in an automatic vehicle. It can
reduce CO2 emissions by 12% compared to a manual / automatic, and it can improve the 0 – 60mph time by 1
second compared to an identical car fitted with a manual transmission. It is also cheaper to manufacture, and
weighs less when fitted [21]. For all these reasons, we are going to fit a manual Zeroshift transmission to our
Range Rover Sport.
Figure 34: An exploded view of a pair
of drive rings between 2 gears [21]
Figure 35: Zeroshift compared to a manual gear
change [22]
Figure 36: Fuel economy and acceleration
performance of various transmissions
technologies [22]
Page | 25
4. Main Design Parameters The main design parameters for the driveline and transmission are:
Gear Ratios
Number of Gears
Gear Ratios
The gear ratio is the ratio of the teeth on the output/driver gear to the number of teeth on the input/driven
gear.
There are a number of key principles that the gearbox ratio selection is influenced by:
The first gear ratio defines the maximum torque, which is required to accelerate the car from
stationary
The top gear has to be chosen to ensure as minimal a stress on the engine as possible. This will give it
better economy at cruising speeds.
Each gear ratio should be relatively close to the previous ratio, in order to make driving smoother
Gear Ratio Selection
The sample Excel spreadsheet, with associated equations, shows how the first (i1) and second (i2) gear ratios
have been calculated for our model. The number of teeth for the 6 gears have been estimated initially and
then iterated until a correct value for the second gear ratio, i2, has been found. The first gear ratio of 4.40 has
been estimated at a larger value than the 4.17 first gear ratio of the old range rover sport. This is due to the
increased torque and power of the updated engine.
Iteration i1 z1 z2 z5 z6 z7 z8 A (mm)
A' (mm) i2 (z2/z1) (z6/z5)*i (z8/z7)*i
1 4.40 36 43 57 26 65 19 126 124.5 2.62 1.2 1.2 1.3
2 4.40 37 44 58 27 66 18 126 127.5 2.55 1.2 1.2 1.2
3 4.40 38 45 58 27 67 18 127.5 127.5 2.54 1.2 1.2 1.2
Distance between two shafts:
( )
( ), where module of gears, m = 3
By definition the following must be equal for correct gear ratios:
(Z2/Z1) = (Z6/Z5)*i2 = (Z8/Z7)*i1, and A = A’
Number of Teeth
Distance
between Shafts
Table 10: Calculated Gear Ratios by Iteration
Page | 26
The second gear ratio has been proposed as 2.54. This is larger than the old range rover’s second gear ratio of
2.34. This is an intended increase due to the higher torque required for the second gear in our updated model.
The method for obtaining the other gear ratios is the same as for the second gear.
The distance between the shafts in the old range rover model can be determined by:
√
= 127.23
This is very similar to the A = 127.5 that has been calculated for the new model, so it is acceptable.
Number of Gears
In terms of the number of gears, more gears imply:
Performance and fuel economy of the vehicle are improved
The overall mass of the gearbox would be dramatically increased
The structure of the gearbox is more complex
The gear ratios of the other gears can be reduced to give the same fixed lowest gear ratio
The old 4.2L range rover sport and the 2010 5.0L versions make use of 6 gears in the automatic gearbox. We
will maintain this 6 gear gearbox because if it can be selected for the 2010 model with a higher torque and
power rating than our upgraded model, we know it can continue to be utilised in our 4.4L model.
As a result of the analysis, the following gear ratios have been proposed:
Gear 1st 2nd 3rd 4th 5th 6th
Ratio 4.40 2.54 1.64 1.21 0.97 0.75
Where: Te max = Max Torque of Engine, i1 = First gear
ratio, ηg = transmission efficiency
Table 11: Calculated Gear Ratios
Page | 27
5. Powerflow through the Driveline
We are calculating the torque and speed transmitted to the output shaft of the gearbox at a typical engine
operating condition in each gear. The operating condition we have chosen is going to be when the engine is at
3000 rpm. From Figure 4, we can see that at 3000 rpm the torque transmitted from the engine is 600 Nm. The
new proposed gear ratios are used for analysis.
Output torque: T2 = T1 * N1/N2
Output speed: W2 = W1 * N2/N1
Gear 1 2 3 4 5 6
Torque in input
shaft (Nm) 600 600 600 600 600 600
Torque in output
shaft (Nm) 2640 1520 980 730 580 450
Speed in input
shaft (RPM) 3000 3000 3000 3000 3000 3000
Speed in output
shaft (RPM) 680 1180 1830 2480 3090 4000
Power flow
transmitted from
engine to input shaft
Powerflow transmitted
from output shaft to
transfer box
Power flow
transmitted from
input shaft to 1st gear
Power flow
transmitted from 1st
gear to output shaft
Input Shaft
Output shaft
Powerflow in
Powerflow out
Gears
Figure 37: Schematic diagram of the
Powerflow through our automatic gearbox
T1 = Input Torque
W1 = Input speed
N1/N2 = Gear ratio
Table 12: Powerflow Through Gears
Page | 28
6. Vehicle-Powertrain Simulation In accordance with the ZF 6HP28 data sheet the gearbox has a gear shift time of 40 milliseconds
The shift strategy algorithm along with the path of acceleration performance in each gear and the
overall acceleration performance of the vehicle are shown separately below:
The strategy of the simulation is to implement a delay in the gear shift by 15 milliseconds to achieve
maximum acceleration in each gear as described in the chart below:
Figure 39: Acceleration vs. Time Diagram for Different Gears
Figure 38: Gear Shifting Strategy
Second Gear
Fourth Gear
Third Gear
First Gear
Sixth Gear
Fifth Gear
Page | 29
Simulation:
A simulation model has been made using MATLAB Simulink.
All of the friction factors such as road friction, drag friction, rolling resistance and hill gradient have
been considered in the simulation and the improved quantified values are listed in the table below
along with the simulation algorithm:
Figure 40: Acceleration vs. Time Diagram After Considering Gear Shifting Strategy
Figure 41: Simulation Algorithm
Page | 30
Drag Coefficient Cd = 0.37 Engine Moment of
Inertia Ie = 1.24
Road Frictional
Coefficient b = 1.32
Drive shaft moment of
inertia Id = 0.132
Rolling Resistance rrc = 0.01 Final drive ratio Nf = 3.54
Effective Area for
Drag A = 1.956*1.5 Drive wheel radius (m) r = 0.36449
Average Air Density ro = 1.25 Height of CG h = 0.60
Curb Vehicle mass +
(Max Load)
M = 2570+ (550)
KG
Distance of front axle
from CG (m) b = 1.32
Maximum Up Hill
angle (Deg) 40°
Maximum Up Hill Angle
at 30 MPH (DEG) 15°
The maximum speed is electronically limited to 250 KMH for safety reasons.
From the graph, we can see that our vehicle accelerates from 0-60 MPH (0-100 KPH) in 6.6 seconds.
Fuel Consumption Rate
The fuel consumption rate has been accurately calculated considering transmission efficiency.
The goal of the design is to achieve a fuel consumption rate of over 20 MPG and 17.5 MPG for the
original model
Figure 42: Speed vs. Time Graph Showing 0-60MPH Acceleration
Table 13: Data Used for Simulation
Page | 31
The formulas used are listed below:
The results are shown in the following chart:
Sixth Gear
Fifth Gear
Fourth Gear
Third Gear
Second Gear
First Gear
Figure 43:Equations Used for Fuel Consumption Simulation [23]
Figure 44: Fuel Consumption (km/litre) vs. Time for Different Gear Ratios
Page | 32
As it is shown in figure 44 the first gear has the best fuel consumption and sixth gear has the worst
fuel consumption. Note that the gear ratios from 3rd to 6th gear have been estimated according to the
1st and 2nd gear ratios which were calculated previously.
The average fuel consumption is 7.03 Km/Litre which converts to 20.01 MPG satisfying the initial goal.
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Page | 34
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