CONTENT

PAGE
Abstract

1.0 Introduction

2.0 Objective

3.0 Problem statement

4.0 Scope

5.0 Methodology

5.1 Description of the Product

5.1.1

What is an engine block?

5.1.2

Functional Requirements of a Cylinder Block

5.2 Required Material Properties

5.3 Metals Used in the Manufacture of the Cylinder Blocks

5.4 Mechanical Properties of the Alloys

5.5.1 Gray Cast Iron Alloys

5.5.2 Compacted Graphite Cast Iron
5.5 Casting Processes

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5.6.1 Green Sand Molding

5.6.2 Lost Foam Casting
6.0 Summary

14

7.0 Reference

15

FIGURE CONTENT

PAGE
Figure 5.1: Cylinder blocks in V, inline, and horizontally-opposed

configurations
Figure 5.2: BMWs S54 inline-6 engine, which uses a gray cast iron

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engine block [9]

Figure 5.3: Ford/Peugeots 2.7-liter V6 uses a cylinder block manufactured

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out of compacted graphite cast iron

Figure 5.4: The first stage of green sand molding, a mixture of silica sand,

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clay, and water is poured into a defined pattern framed with metal
.
Figure 5.5: Graphical description of the last 6 of 7 methods of the lost foam

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casting method

TABLE CONTENT
PAGE
Table 5.1: Comparison of tensile strength and modulus of elasticity

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of gray cast iron and compacted graphite cast iron

Abstract
Until recently, cast iron and aluminum alloys have been the preferential materials used to
Manufacture most diesel and conventional gasoline-powered engine blocks. However, with a
greater emphasis on increasing the efficiency of the engine via weight reduction, manufacturers
have begin to look for alternative alloys that are lighter than cast iron and aluminum alloys,
while retaining the necessary strength to withstand the forces of an engine. As of late, new
Manufacturing processes have been developed that have engendered two new alloys suitable for
use in an engine block, magnesium alloy AMC-SC1 and compacted graphite cast iron (CGI). In
this paper, the functional requirements of the engine block, the processes used to manufacture the
part, and the mechanical properties of the alloys will be discussed.

1.0

Introduction
The first successfully working internal combustion engine used in an automobile was

built by Siegfried Marcus in approximately 1864 [1]. It was an upright single-cylinder, two
stroke petroleum-fueled engine that also utilized a carburetor to deliver fuel to the engine. The
engine was placed on a cart with four wheels and successfully ran under its own power. Not
only has Marcus produced the first engine that is the direct predecessor to todays engines, he
had also built the first automobile in history, some 20 years before Gottlieb Daimlers
automobile. Todays engines are an integral component of an automobile that are built in a
number of configurations and are considerably more complex than early automotive engines.
Technological innovations such as electronic fuel injection, drive-by-wire (i.e., computer
controlled) throttles, and cylinder-deactivation have made engines more efficient and powerful.
The use of lighter and stronger engineering materials to manufacture various components of the
engine has also had an impact; it has allowed engineers to increase the power-to-weight of the
engine, and thus the automobile.
Common components found in an engine include pistons, camshafts, timing chains,
rocker arms, and other various parts. When fully stripped of all components, the core of the
engine can be seen: the cylinder block. The cylinder block (popularly known as the engine
block) is the strongest component of an engine that provides much of the housing for the
hundreds of parts found in a modern engine. Since it is also a relatively large component, it
constitutes 20-25% of the total weight of an engine [2]. Thus there is much interest in reducing
the blocks weight. Many early engine blocks were manufactured from cast iron alloys primarily
due to its high strength and low cost. But, as engine designs became more complicated, the
weight of the engine (and the vehicle) had increased.

Consequently, the desire among

manufacturers to use lighter alloys that were as strong as cast irons arose. One such material that
was being used as a substitute was aluminum alloys. Used sparingly in the 1930s (due to
problems with durability) [3], aluminum alloy use in engine blocks increased during the 1960s
and 1970s as a way to increase fuel efficiency and performance. Together, these two metals
4

were used exclusively to fabricate engine blocks. As of late, however, a new material
process has made a magnesium alloy suitable for use in engines. The alloy, called AMC-SC1,
weighs less than both cast iron and aluminum alloys and represents new possibilities in engine
manufacturing. A new manufacturing process have made compacted graphite cast iron (CGI) a
viable alternative to gray cast iron for the manufacture of diesel engine blocks. Like magnesium
alloys, this material offers a higher strength and lower weight than gray cast iron. In this paper,
materials used to manufacture engine blocks for passenger vehicles will be discussed. The
discussion of the component, its functional requirements, and the materials used to manufacture
the part are included. The mechanical properties of the individual alloys will be incorporated, as
well as the manufacturing processes used to fabricate the component.

2.0

Objective
(i)
(ii)
(iii)

3.0

To understanding manufacturing process to make an engine block.

To determine the material uses in production of an engine block
To compare
Problem statement

(i)
(ii)
4.0

To determine the most efficient process to make an engine block

To find the suitable material used in making engine block.
Scope

(i)
(ii)

For automotive manufacturer only.

Engine diesel and petrol only.

5.0

Methodology

5.1 Description of the Product

5.1.1

What is an engine block?

An engine block is the core of the engine which houses nearly all of the components required for
the engine to function properly. The block is typically arranged in a V, inline, or horizontallyopposed (also referred to as flat) configuration and the number of cylinders range from either 3
to as much as 16. Figure 1 shows engine blocks with V, inline, and horizontally opposed
configurations.

Figure 5.1: Cylinder blocks in V, inline, and horizontally-opposed configurations

5.1.2

Functional Requirements of a Cylinder Block

Because engine blocks are a critical component of an engine, it must satisfy a number of
functional requirements. These requirements include lasting the life of the vehicle, housing
internal moving parts and fluids, ease of service and maintenance, and withstand pressures
created by the combustion process.

5.2 Required Material Properties

In order for an engine block to meet the functional requirements listed above, the engineering
material(s) used to manufacture the product must possess high strength, modulus of elasticity,
abrasion resistance, and corrosion resistance. High strength is a particular concern in diesel
engines, since compression ratios are normally 17.0:1 or higher (compared to about 10.0:1 for
conventional engines). The material should also have a low density, thermal expansion (to resist
expanding under high operating temperatures), and thermal conductivity (to prevent failure under
high temperatures). Good machinability and cast ability of the metal alloy are also important
factors in selecting the proper material, as the harder it is to machine the product, the higher the
costs of manufacturing. In addition to the previously mentioned properties, the alloys must
possess good vibration damping to absorb the shuddering of the moving parts.

5.3 Metals Used in the Manufacture of the Cylinder Blocks

Based on the functional requirements of the cylinder block and the material properties required
to meet the functional requirements, industries have used cast iron and aluminum alloys to
manufacture the blocks.

Cast iron alloys are used because of the combination of good

mechanical properties, low cost, and availability.

Certain aluminum alloys combine the

characteristics of iron alloys with low weight, thereby making the material more attractive to
manufacturers who are seeking a competitive edge. Compacted graphite cast iron is lighter and
stronger than gray cast iron, making the alloy a more attractive alternative to the latter in the
production of cylinder blocks, particularly in diesel engines. Magnesium alloys, which were
previously unsuited for use as an engine block material, have the advantage of being the lightest
of all the mentioned metals, yet still retains the required strength demanded by a block.

5.4 Mechanical Properties of the Alloys

Both conventional and diesel-fueled cylinder blocks are subjected to thermal strains,
aggressive wear conditions, and high fatigue stresses that an alloy must be able to endure.
Engineers must be able to select the proper material that meets the mechanical requirements
previously set. For example, the required mechanical properties for a typical aluminum engine
block includes an ultimate tensile strength of 245 MPa, yield stress of 215 MPa, and fatigue
strength of 60 MPa. Listed in the following sections are alloys that are current being used to cast
engine blocks and their mechanical properties.

5.4.1 Gray Cast Iron Alloys

Gray cast iron alloy have been the dominant metal that was used to manufacture conventional
gas-powered engine blocks. Though extensive use of aluminum alloys has diminished the
popularity of this material, it still finds wide use in diesel-fueled blocks, where the internal
stresses are much higher. Gray cast iron alloys typically contains 2.5-4 wt.% carbon and 1-3 wt.
% silicon, 0.2-1.0 wt.% manganese, 0.02-0.25 wt.% sulfur, and 0.02-1.0 wt.% phosphorus [8]. It
has excellent damping capacity, good wear and temperature resistance, is easily machinable, and
is inexpensive to produce. However, gray cast irons are relatively weak and are prone to fracture
and deformation. Due to these problems, compacted graphite iron has recently begun to compete
with gray cast iron as the choice material to produce diesel engine blocks. Figure 2 shows the
BMW S54 inline-6 used in their high performance M3 coupe. It is interesting to note that the
cylinder block for this engine is constructed from gray cast iron, whereas the block for the BMW
M54 engine, the basis of architecture of the S54, was made of aluminum alloy. One possible
reason why the S54 block was made from gray cast iron was the need for a stronger material that
could tolerate the higher performance levels (the S54 produces 333 brake horsepower and has a
maximum engine speed of 8000 rpm, whereas the M54 produces 184-225 brake horsepower with
a maximum engine speed of 6500 rpm).

Figure 5.2: BMWs S54 inline-6 engine, which uses a gray cast iron engine block

5.4.2 Compacted Graphite Cast Iron

Compacted graphite cast iron (CGI), which was accidentally discovered while trying to produce
ductile cast iron, possesses higher tensile strength and elastic modulus than gray cast iron due to
the compacted graphite found on the microstructure of CGI. Table 1 shows the comparison
between the strengths and modulus of elasticity of gray cast iron and CGI. As seen in Table 1,
gray cast iron has a lower tensile strength than CGI, despite its higher weight.

Tensile strength, MPa

Modulus of elasticity, GPa

Gray cast iron

160-320
96-110

Compacted graphite cast iron

300-600
170-190

Table 5.1: Comparison of tensile strength and modulus of elasticity of gray cast iron and
compacted graphite cast iron
Like gray cast iron, compacted graphite cast iron has good damping capacity and thermal
conductivity, but its difficulty to machine has limited the wide-scale use of CGI. A new
manufacturing process, however, has opened the way for larger applications of CGI. The
development of rotary insert tools has increased the life of the tools used to machine the metal,
thus allowing manufacturers to use CGI without worrying about purchasing new tools. Initial
projections of 150,000 diesel engines produced (by Ford and Peugeot) per year are an indication
that manufacturers are embracing the use of CGI as the material to produce cylinder blocks.
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Figure 5.3: Ford/Peugeots 2.7-liter V6 uses a cylinder block manufactured out of

compacted graphite cast iron

5.5 Casting Processes

There are two methods used to cast engine blocks for all materials: green sand molding or
lost foam casting. The latter, pioneered by General Motors for their Saturn vehicles, have
become more popular due to its capability to produce near net shape components, provide tight
tolerances for critical components, and reduce machine maintenance and cost [19]. Green sand
molding, however, is still widely used in industry as material costs are low and most metals can
be cast by this method

5.5.1 Green Sand Molding

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A part of the sand casting family that also includes dry-sand molds and skin-dried molds,
green sand molding the common method to cast engine blocks. The term green denotes the
presence of moisture in the molding sand [20]. Figure 2 demonstrates the first stage of green
sand molding. From Figure 2, a combination of silica sand, clay, and water poured in one-half of
the block pattern with a wood or metal frame. The mold is then compacted by squeezing or
jolting, and the process is repeated for the other half of the mold. A core consisting of hardened
sand is used for support. Then, molten cast iron, aluminum, or magnesium alloy is poured into
the combined molds and solidifies. Once the latter part has been completed, the molds are
removed, and the cylinder block is cleaned and inspected. Heat treatment of the block is then
undertaken to improve the mechanical properties of the alloy for suitable use.

Figure 5.4: The first stage of green sand molding, a mixture of silica sand, clay, and water is
poured into a defined pattern framed with metal.

5.5.2 Lost Foam Casting

Lost foam casting is a more reliable and efficient casting technique of the manufacture of
engine blocks than green sand molding. The technique begins with the use of polystyrene beads
12

placed in pre expanders for wet expansion to control bead size and density to produce four
separate block moldings to be glued together to form the final mold. Next, the metal tool is
preheated to remove any moisture and then filled with the beads. The tool is then heated via
steam and placed in an autoclave, where it is subjected to high pressures in order to create the
molds. The tool is removed from the autoclave and immersed in water to finish the moldings.
Precise control over the heating and cooling aspect ensures dimensionally accurate, smooth and
strong molds. If the tool was not heated before the beads were injected, the results would be
rough finishes in the molds with low-strength sections. If the tool and beads stay heated for an
extended period of time, or is not cooled enough, the beads become over fused, which
produces surface variations in the moldings. If the tool has been inadequately cooled, the molds
will contain variations in dimensions.

Figure 5.5: Graphical description of the last 6 of 7 methods of the lost foam casting method
From Figure 3, once the individual molds are glued together, the assembly is placed in a
vat with water-based ceramic liquid to prevent molten metal from destroying the mold, stiffen
the assembly, and provide a smooth finish. The assembly can also be sprayed with the ceramic
liquid, but is a time-consuming process. Next, the coated foam engine block is filled with sand,
compacted, and immersed in the molten metal alloy. Once cooled, sand is removed from the
metal casting, cleaned, and undergoes heat treatment to increase the mechanical properties of the
block. Finally, coolant and oil passages are machined into the block.
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6.0

Summary

While aluminum and cast iron alloys have dominated the market for engine block materials for
many years, new materials that were either once impossible or too expensive to consider have
now become reality. Over the past couple of years, new machining processes and material
fabrication have increased the use of compacted graphite cast iron over gray cast iron as the
material of choice to produce cylinder blocks for diesel- and regular petroleum-fueled vehicles.
But perhaps the greatest innovation in engine block technology is the production of a magnesium
alloy that is able to perform under the difficult conditions an engine is put through. AMC-SC1
magnesium alloy will be able to increase fuel efficiency and power-to-weight ratios of
automotive engines while decreasing emission levels. Though this may be a significant impact
for the internal combustion engine, it faces new challenges. Engines powered by fuel cells,
hydrogen, and electricity are extremely efficient vehicles that have become viable within the last
decade. As automobiles advance further into the 21st century, the role of the internal combustion
engine may possibly diminish due to these new advances, despite the use of lighter alloys.

7.0

References
1. ASME Landmark: Additional Information on Marcus car, [Online], 20 March 2005-last
update, Available: http://www.asme.org/history/attachments/marcus1.html
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2. Keay, Sue: Diet of Australian metal lightens cars and pollution, Media release, 14
October 2002.
3. Anyalebechi, P.N., Private Communication.
4. Anatomy of an Engine the New Northstar V8, [Online], 7 April 2005-last visited,
Available: http://www.autospeed.com/cms/A_1569/article.html.
5. 5. In Search of Light-Weight Components, [Online], 6 April 2005-last update,
Available: http://www.moderncasting.com/archive/WebOnly/1102/AL1102.asp.

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