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Bearing Design for a Volkswagen 2.0 TFSI Engine

MEEN 4323
Mechanical Design II
Department of Mechanical Engineering
Fall 2024

Uy Le ule1@lamar.edu
Brian Mai bmai2@lamar.edu
Alberto Perales aperalespere@lamar.edu
Malek Prudhomme mprudhomme@lamar.edu
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Abstract:
The purpose of this report is to design and analyze the clearance between the main journal
bearing and the shaft of an engine selected by the group. The report is structured with thorough
explanations regarding the engine type, data necessary for calculations, and how the crankshaft
operates with force all explained in the introductory sections of the report to allow for an
understanding of the concept before proceeding.
The core section of the report falls on the design of the bearing itself with explanations of the
detailed results for the differing variables and comparisons between the manufactured
‘theoretical’ bearing and the designed ‘experimental’ bearing in the results and discussion
sections of the report. For this purpose, data was acquired for the necessary calculations from
professional and academic sources. The data collected would be allotted into several
mathematical equations to find values that are also essential to the experiment, like the upper and
lower limit of the designed bearing clearances. The oil utilized inside of the engine, and that
variables such as viscosity would be based upon, is SAE graded 5W-40 oil with an operating
temperature of 100° C. Once all the data was collected, the experiment began, and the use of
Microsoft Excel and mechanical design graphs allowed the formation of a table with data for
different clearance values for the bearing.
The results showcase the differences between the theoretical and experimental bearings with the
results being within reason. The accuracy when compared to the manufacturer’s specifications is
noticeable with an approximate percentage error of 6% for the minimum clearance and 6.1% for
the maximum clearance. The reasoning behind the procurement of the favorable results, the
meaning behind them, and possible improvements will all be explained in the appropriate
sections of the report.
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Table of Contents:

Abstract 2
Introduction 4
Nomenclature 6
Crankshaft Force Analysis 7
Bearing Clearance Analysis 8
Crankshaft Main Bearing Clearance Design 9
Discussion 10
Conclusion 10
References 11
Appendix 12
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Introduction:

Figure 1: Volkswagen 2.0L TFSI Engine

The Volkswagen 2.0L TFSI engine is the engine the group selected with a goal of
creating an experimental design of a crankshaft bearing. It is a 2.0 liter inline four-cylinder
engine that was created in 2008 and was in production from 2008 till 2014 for varying
Volkswagen and Audi automobiles before being upgraded to an improved model with a new
generation label. The engine block consists of cast iron material with a direct injection fuel
system. The engine has a maximum power output of 197 hp at 5100 RPM and a maximum
torque of 280 Nm at 1700 RPM. The main journal diameter is 54 mm, the piston diameter is
82.51 mm, and the bearings have a clearance of 0.02 to 0.06 mm.
The engine itself would have to be designed with considerations regarding its safety and
environmental effect to lead to a positive impact within society. One of the key aspects of an
engine is its reliability with emphasis on preventing engine failure when one is travelling on the
road. To circumvent this threat, a few key aspects must be integrated into the design. The
bearings will be designed while adhering to SAE standards, a large set of internationally
recognized guidelines to help ensure the safety, quality, and reliability of products in the
automotive industry. By utilizing SAE graded 5W-40 oil and following standards regarding
engine power and testing, the bearings can be created with the proper lubrication and the correct
industry guided standards. Another method for enhancing the safety of the design would be to
ensure the method of cooling the engines down is efficient over a long period of time. A
combination of cooling fans and a water pump will push air through the radiator and force
coolant throughout the system respectively. The environmental impact of the engine itself is
another impact factor with an importance on supporting environmental sustainability. Two
different methods will be considered to help bolster the eco-friendliness of the design. Firstly, the
possibility of utilizing materials, such as carbon steel, could allow parts of the engine to gain
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corrosion resistance and increased durability which would lead to a reduction in engine part
replacement. This effect would lead to a decrease in product waste as the parts themselves would
possess a longer lifespan. The other aspect is that the bearings would possess a low amount of
friction by the use of proper lubricant. Sufficient lubrication will prevent wear and tear which
can have a direct impact on fuel efficiency which would be detrimental to the environment as the
amount of greenhouse gas emissions would increase from the automobile in question. After the
exploration of possible societal impact factors and with the data gathered from differing
automotive sources, work could begin on designing different clearances between the main
journal bearing and the shaft in the engine.
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Nomenclature:
Symbol Unit Description
2
A mm Area
c mm Clearance
D mm Diameter
f - Friction Coefficient
ho mm Minimum Film Thickness Variable

L mm Length

n rps Rotational Speed

P Pa Pressure

Pf W Friction Power

Q mm /s
3 Total Flow Rate

Qs mm /s
3 Side Flow Rate

q J /kg−° C Specific Heat Capacity

R mm Radius

T avg °C Average Temperature

Tf N*m Friction Torque

∆t °C Temperature Rise

N Radial Load
W
- Pi
π
mPa*s Viscosity
μ
kg /m
3 Density
ρ
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Crankshaft Force Analysis:

Figure 2: Volkswagen 2.0L TFSI Crankshaft

The 2.0 TFSI is an inline-4 turbocharged engine that produces 200 horsepower. As an
engine utilizing the Otto cycle, each of these cylinders undergoes four stages that result in power
output: a) intake, where the combustion fuel and air are let in, b) compression, where this
mixture is compressed by the movement of the piston upwards, c) combustion, where the spark
from the spark plug ignites the compressed mixture, and d) exhaust, where the byproducts of
combustion are released from the cylinder, resetting the process.
An inline cylinder arrangement means that instead of being situated at an angle relative to
the crankshaft, each piston instead sits directly on top of the crankshaft. This is important due to
how the forces are transmitted from the piston to the crankshaft. A connecting rod links the
piston to the crankshaft, with a big-end bearing at the crankshaft end and a small-end bearing at
the piston end. The big-end bearing is of particular importance, as this is a journal bearing that
must rotate smoothly to ensure optimum engine performance. When the piston moves due to
combustion, the force at the big end bearing is tangent to the length of the offset between the big
end bearing and the crankshaft axis, translating the vertical motion of the piston into a turning
moment that drives the crankshaft. This force is a function of the gas pressure on the piston
head, as well as the friction resistance, thrust on the sides of the cylinder chamber, and even the
weight of the piston itself.
Also, on the body of the crankshaft itself are 5 main journal bearings, larger in size than
the big-end bearings. These bear the brunt of the load in the crankshaft and are the subject of
investigation in this report.
For simplification of force analysis calculations, it has been assumed that only one
cylinder provides power input to the crankshaft. During regular operation, the cylinders follow a
1-3-4-2 firing order, ensuring that there is always some power input into the shaft.
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Bearing Clearance Analysis:

Hydrodynamic bearings depend on the factors of viscosity ( μ), rotating speed (n ), and
bearing unit load ( P). The bearing characteristic number, S, utilizes these parameters to find the
corresponding variables in the relevant design charts for hydrodynamic bearings. Using a known
length and diameter of 24.9 mm and 54 mm respectively, an L/D ratio of ½ can be assumed. The
optimum zone shown in Figure 4 shows the area of best performance for journal bearings. By
following the curve for ½ L/D ratio within the optimum zone, the bearing characteristic numbers
of limits were found (0.04 and 0.36). The friction torque, friction power, and temperature rise of
the oil were also considered when choosing a suitable design.
W
P= (Eq.1)
LD

( )
2
μn R
S= (Eq. 2)
P c

WfD
Tf= (Eq. 3)
2

nTf
Pf = (Eq. 4)
9549

Hf
∆ t= (Eq. 5)
Qs q ρ
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Table 1: Hydrodynamic Bearing Design at Optimum Main Journal

Bearing Clearance Zone

Main Bearing Minimu Minimu Frictio Coefficien Flow Flow Rate Flow Side Flow
Journal Characteristi m Film m Film n Ratio t of Variabl Rati Rate
Bearing c Number Thicknes Thicknes Friction e o
Clearanc s Ratio s
e Variable
c (mm) S ho h o (mm) R f Q Q Qs Qs
∗f
c c RcnL 3
(mm /s) Q (mm3 /s )
0.0188 0.36 0.42 0.0079 9.50 0.0066 4.70 5039.3389 0.72 3628.3240

0.0199 0.32 0.41 0.0082 8.75 0.0064 4.80 5458.7500 0.74 4039.4750

0.0221 0.26 0.36 0.0079 7.00 0.0057 4.90 6182.1048 0.76 4698.3997

0.0252 0.20 0.32 0.0081 5.50 0.0051 5.10 7336.3854 0.80 5869.1083

0.0301 0.14 0.28 0.0084 4.50 0.0050 5.20 8940.5921 0.84 7510.0974

0.0398 0.08 0.18 0.0072 3.20 0.0047 5.30 12054.739 0.90 10849.265
6 6
0.0563 0.04 0.12 0.0068 1.80 0.0038 5.60 18012.956 0.93 16752.049
0 1

Calculated values inside the optimum zone

WfD ( 5520 ) ( 0 .0051 ) ( 0 . 052 )
Tf= = =0 . 7359 N∗m
2 2

n T f ( 5000 ) ( 0. 7359 )
Pf = = =0 . 3853 kW
9549 9549
Hf 385.3
∆ t= = =34.291° C
Qs q ρ ( 5869∗10−9)(2.38)(804.5∗103 )
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Discussion:

With the design of the main journal bearing, industry graded SAE 5W-40 oil was utilized
at an operating temperature of 100° Celsius. With this value, the chart in Figure 3 could be used
to acquire the corresponding absolute viscosity amount, (8.5 x 106 Pa • s), to proceed with the
calculations for the flow rate and film thickness. The design produced a clearance of 0.0188 to
0.0563 mm by utilizing the bearing clearance equation with known variables for the main journal
radius, viscosity, revolutions per second, the upper limit of the bearing characteristic number,
and the operating pressure. From here, the mechanical design charts listed in the appendix
section allowed for the discovery of important data for the variables of the minimum film
thickness ratio and variable, the coefficient of friction, the flow variable, and the flow ratio. With
the data obtained, comparisons were made between the designed bearing and the theoretical
bearing with the clearances for the designed bearing possessing a 6% error rate from the
manufactured design. This could have been due to an error in calculations with one of the
academic formulas or possibly an error in the data collection for use within the formulas. Despite
these errors, the designed bearings possess a degree of accuracy, and the associated data allows
for an understanding of the values for different variables for each bearing size within the
optimum zone. The friction is also noticeably decreasing as the bearing size increases with
varying friction ratios. Attention should be centered towards the friction ratio as a result with
smaller values denoting lower friction losses. The values between 0.045 to 0.05 would be the
most ideal sizes for the bearing in this case. Despite the lower friction losses, the flow rate of the
lubricant increases as those friction losses increases which can denote potential instability issues
and pressure changes.

Conclusion:

In summary of the scope of the project, the main journal bearing clearance, which was
obtained through the usage of Figure 4, was found to be within a range of 0.0188 to 0.0563 mm.
These values, although not the same as the manufacturer’s data, possessed accuracy within a 6%
error margin. With the friction values decreasing as the clearance size increases, the bearings that
fall between 0.045 to 0.05 would boast lower friction losses due to the smaller friction ratios.
This leads to a higher flow rate of the lubricant within the main journal bearing which can cause
pressure changes within the engine. With a summary of the overall findings obtained during the
experiment, the success of the designed bearing can be attributed to proper data analysis and
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usage of academic formulas. The Volkswagen 2.0L TFSI engine is a reliable engine that was and
still is utilized today in the automotive industry with an efficient crankshaft system in place
within.

References:

[1] 2.0 TSI/TFSI EA113 engine - in-depth look at design and reliability. MotorReviewer. (n.d.).
https://www.motorreviewer.com/engine.php?engine_id=5

[2] Bearing clearance and oil viscosity explained: K1 Technologies. K1 Technology. (2023,
August 4). https://www.k1technologies.com/k1-blog/bearing-clearance-and-oil-viscosity-
explained/#:~:text=With%20a%20static%20bearing%20clearance,oil%20for%20the
%20following%20rotation

[3] Juvinall, R. C., & Marshek, K. M. (2017). Fundamentals of Machine Component Design.
John Wiley & Sons.

[4] Kopeliovich, D. (n.d.). Engine Bearings and how they work. King Bearings.
https://www.kingbearings.com/wp-content/uploads/2014/10/Engine-Bearings-and-how-
they-work.pdf

[5] SAE International. (n.d.). J2723_202110: Engine Power Test Code - engine power and
Torque Certification - SAE International. SAE.
https://www.sae.org/standards/content/j2723_202110/

[6] Volkswagen. (n.d.). Quick Reference Specification Book.

https://static.nhtsa.gov/odi/tsbs/2012/MC-10156122-9999.pdf
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Appendix:

Figure 3: Viscosity versus Temperature Curves for Typical SAE Graded Oils
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Figure 4: Chart for Minimum-Film-Thickness Variable

Figure 5: Chart for Coefficient-of-Friction Variable

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Figure 6: Chart for Flow Variable

Figure 7: Chart for the Ratio of Side Flow to Total Flow

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Table 2: Volkswagen 2.0 TFSI Engine Optimum Performance

Manufacture Model Pressure Temperature n (rpm)

r (MPa) (°C)
Volkswagen 2.0 TSI 4.156 100 5100

Table 3: Volkswagen 2.0 TFSI Engine Comparison

Main Journal Main Journal

Bearing Bearing
Clearance (mm) Clearance (mm)
minimum maximum
Known 0.02 0.06
Values
Calculated 0.0188 0.0563
Values
Percent Error 6 6.1666

Sample Calculations:
Oil Type: 5W40

Operating Temperature, T avg: 100 °C

Find the viscosity from the SAE 40 curve in Figure 3

Viscosity, μ: 8.5 mPa*s

Operating Pressure, P: 4156000 Pa

Piston Diameter, D p: 82.51 mm

2
π D p π (82.51)2 3 2
Piston Area, A p = = =2.346∗10 mm
4 4
Journal Diameter, D: 54 mm
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Journal Length. L: 24.9 mm

Journal Area, A j=LD= (24.9 )( 54 )=1344.6 mm 2

P 4156000 3
Radial Load, W = = =5.52∗10 N
A j 1344.6

L 24.9
L/D Ratio, = =0.461
D 54

The following calculations use an L/D ratio of ½ for simpler computations

The upper and lower limit of the bearing characteristic number inside the optimum zone were
calculated using Figure 4

Lower limit S, S1=0.04

Upper limit S, S2=0.36

Operating RPS, n: 85 RPS

To find the upper and lower limit of the designed clearances

S=
P c ( )
μn R 2
→ c=
SP √
R2 μn

Smaller clearance, c mas =

√ √
R 2 μn
S2 P
=
(27¿¿ 2)(0.0085)(85)
(0.36)(4156000)
=0.0188 mm ¿

Higher clearance, c min =

√ √
R 2 μn
S1 P
=
(27¿¿ 2)(0.0085)(85)
(0.04)(4156000)
=0.0536 mm ¿