New 4B11 Turbocharged Engine

Yoshihiko KATO* Kenta TOHARA* Hiromi AKEBO*

Abstract
Mitsubishi Motors Corporation (MMC)’s newly developed inline 4-cylinder turbocharged engine
for the LANCER EVOLUTION X is introduced. This new 4B11 turbocharged engine (2 L) attained
the 12.5 kg weight reduction thanks to an aluminum die-cast cylinder block and direct-acting valve
train. A variable valve timing device MIVEC (Mitsubishi Innovative Valve-timing Electronic Control
System) is equipped not only at the intake side but also at the exhaust side in this engine. This
makes it possible to set the best valve timing for overall engine speed and improve performance,
fuel economy and exhaust emissions. Furthermore, the low- and middle-speed torque and the
response are dramatically improved by reducing pressure drops in the intake and exhaust systems
and by revising the turbocharger specifications. Regarding environmental aspects, this engine
achieved the 50 % reduction level (3;) requirements of Japan’s 2005 Emission Standard by means
of a high-performance metal catalyst, etc.

Key words: Gasoline Engine, MIVEC, Turbocharger, J-ULEV

1. Objectives of the development 3.1 High performance engine consuming less fuel
The technologies adopted to undertake the chal-
The main objective set forth for the development of the lenge of creating a high performance engine consum-
4B11 engine was creating a new turbocharged engine that ing less fuel included the MIVEC system applied to both
is excellent in performance while meeting the needs of the intake and exhaust valve mechanisms (this configura-
times for environmental compatibility. In line with this tion of the MIVEC system was first employed in the 4B1
objective, an aluminum die-cast cylinder block was newly model engines) and optimization in the shape of the
developed with the aim of reducing the weight of the intake manifold as well as of the intake and exhaust
engine. The cylinder block in development also featured a ports. Adoption of these technologies provided the
rear exhaust layout, which is the first of its kind to be intro- effect of distributing an equal amount of air to every
duced for MMC turbocharged engines. The measures cylinder, which in turn enabled the idling speed to be
employed for better fuel economy included the Mitsubishi lowered without compromising the high-speed perfor-
Innovative Valve-timing Electronic Control System (MIVEC) mance of the engine. In addition, the use of an alu-
and a high-efficiency alternator. Started by setting “supe- minum die-cast cylinder block with improved cooling
riority of performance in the motor sports field” as one of efficiency made it possible to further advance the igni-
the concepts to be embodied in the engine, the develop- tion timing and consequently to reduce the fuel con-
ment had generous technical feeds from the motor sports sumption rate. Also, the friction-caused loss of energy
know-how or DNA that MMC had cultivated and accumu- was reduced by the use of full-floating piston pins and
lated through World Rally Championship (WRC) experi- through-holes made in the bulkhead of the cylinder
ences. This know-how was incorporated into this produc- block to lower pressure in the crankcase. Another
tion engine. improvement adopted for higher fuel economy was the
use of a high-efficiency alternator, the first of its kind to
2. Major specifications be used by MMC. On the one hand, while it brought
about higher vehicle performance, the application of
Table 1 compares the major specifications of the these improvements, on the other hand, successfully
two MMC turbocharged engine models, the new 4B11 achieved a fuel economy level equivalent to or higher
and the previously developed 4G63. than that of the LANCER EVOLUTION IX MR, despite the
LANCER EVOLUTION X being 100 kg heavier than the
3. Features former model.
Fig. 1 shows the performance curves of the engines
The following part of this section introduces the on these two vehicle models.
technologies and components adopted to attain the
above-mentioned objectives of the development. Many 3.2 Weight reduction and durability
of the technology and component items contribute to The 4B11 engine has an aluminum die-cast cylinder
two or more improvements as shown in Table 2. block of reduced weight. The biggest challenge with
regard to the employment of this aluminum die-cast

* Engine Designing Dept., Development Engineering Office

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 New 4B11 Turbocharged Engine

Table 1 Major specifications

LANCER EVOLUTION X LANCER EVOLUTION IX MR (Reference)

4B11 (2.0 L) 4G63 (2.0 L)
Displacement (cc) 1,998 1,997
Cylinder bore (mm) 86 85
Stroke (mm) 86 88
Stroke/bore (S/B) ratio 1.00 1.04
Bore to bore pitch (mm) 96 93
Big-end to small-end length of connecting rod (mm) 143.75 150
Compression ratio 9.0 8.8
Red zone speed/over-revolution fuel cut speed 7,000 / 7,600
Fuel used Unleaded premium gasoline
TD05HA-152G6-12T TD05HRA-155G6C-10.5T
Titanium-aluminum alloy turbine wheel and Titanium-aluminum alloy turbine wheel and
aluminum alloy compressor wheel combination aluminum alloy compressor wheel combination
Turbocharger
TD05H-152G6-12T TD05HRA-155G6mC-10.5T
Option Inconel turbine wheel and aluminum alloy Titanium-aluminum alloy turbine wheel and
compressor wheel combination magnesium alloy compressor wheel combination
Cylinder block material Aluminum die-casting Cast iron
Camshaft drive Silent chain-driven Timing-belt-driven
Valve train Direct-acting DOHC, 16 valves, Roller rocker arm DOHC, 16 valves,
continuously variable MIVEC applied to both intake continuously variable MIVEC applied to
and exhaust systems intake system
Balancer shaft None Secondary balancer
Exhaust system layout Rear exhaust Front exhaust
Maximum torque (N·m/min–1) 422 / 3,500 400 (GSR), 407 (RS) / 3,000
Maximum output {kW(PS)/min–1} 206 (280) / 6,500 206 (280) / 6,500

Compliance with exhaust emissions control standard 50 % reduction level (3;) requirement of Japan’s 2000 Emissions Standard
Japan’s 2005 Emissions Standard
Engine weight reduction g12.5 kg* Base weight
* Reduction in weight of engine main body (not including intake and exhaust system parts)

Table 2 Adopted technologies and their purposes

Technology/component High performance, Compactness, Low emissions Low NVH High reliability
low fuel consumption light weight
Aluminum die-cast cylinder block v
Four-bolt fastened bearing cap v v
Semi-closed deck design v v
Continuously variable valve timing system (MIVEC)
v v v
on intake and exhaust sides
Equal-length, short-port aluminum intake manifold v v
Rear exhaust engine layout v v v
Compact-size, large capacity, fine spray injector v v
Disuse of balancer shaft v
Fuel system refinement (optimization of control fuel pressure) v v
Use of long-reach M12 ignition plug v v
High-efficiency alternator v v
High-performance metal catalyst v v

cylinder block was to ensure strength sufficiently shape top deck with bridges to the cylinder block to
durable against operational stress while reducing the minimize the bore deformation of the cylinders under
weight. The first measure to make this possible was stress of high-output operation. Furthermore, a ladder
fastening each of all the five bearing caps to the cylin- frame structure was applied to the cylinder block, which
der block with four bolts to assure strength enough to greatly contributed to the reduction in noise, vibration
withstand high output operation of the engine. The sec- and harshness (NVH). Fig. 2 shows the structure of the
ond measure was the application of a semi-closed cylinder block.

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New 4B11 Turbocharged Engine

Fig. 2 Cylinder block structure

Fig. 1 Engine performance

In addition to the above, other weight reduction

measures were also applied, examples of which are the
adoption of a direct-acting valve train and the disuse of
balancer shafts. As a result, the weight of the new
engine mechanism could be successfully reduced by as
much as 12.5 kg compared with the 4G63 turbocharged
engine.

3.3 Low exhaust emissions

The technologies adopted for simultaneously satis-
fying high performance and low exhaust emission
requirements were compact-size fine spray injectors
and optimization of fuel line pressure. Application of
these technologies enabled improved fuel atomization Fig. 3 Engine response
while maintaining necessary fuel flow rate during high-
output operation and eventually ensured clean exhaust
emissions while the engine stayed capable of deliver- bocharger compressor wheel, a straight type intake sys-
ing high power. Using these technologies in combina- tem and large diameter exhaust system piping featur-
tion with the rear exhaust layout and a high-perfor- ing heightened response performance which is up to 18
mance metal catalyst featuring a shorter activation % faster to respond to accelerator operation than the
time, the new engine successfully reduced exhaust 4G63 turbocharged engine. Fig. 3 compares the engine
emissions of the EVOLUTION X to a level as low as less response characteristics of the LANCER EVOLUTION X
than 1/4 of the EVOLUTION IX, achieving the 50 % and LANCER EVOLUTION IX MR. Fig. 4 shows the
reduction level (3;) requirements of the Japan’s 2005 details of the compressor wheel improvement.
Emission Standard.
3.5 Higher reliability
3.4 Improved engine response Unlike the 4G63 turbocharged engine which uses
An engine’s “high performance” is most often rep- M14 long-reach spark plugs, the 4B11 turbocharged
resented by large maximum output and torque. In the engine uses M12 long-reach spark plugs that enable the
motor sports field, the engine response is another water jackets around the combustion chambers to be
important performance factor. The 4B11 engine incor- expanded for more efficient cooling. This, coupled with
porates such improvements as an optimally shaped tur- the highly heat-conductive aluminum cylinder block,

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 New 4B11 Turbocharged Engine

Fig. 4 Compressor wheel improvement

lowers the fire-contact surface temperature of the new Fig. 5 Cylinder head cross section
engine by approximately 50 ˚C compared with the 4G63
engine, greatly reducing the thermal load upon the
cylinder head. Fig. 5 shows cross sectional views of the
cylinder head.

4. Conclusion

Exhaust emissions, fuel economy and other envi-

ronmental performances of the engine will further
increase their importance in the future. The situation
Yoshihiko KATO Kenta TOHARA Hiromi AKEBO
will thus certainly impose a challenge of simultaneous-
ly nurturing to a still higher level two contradicting fac-
tors, namely high performance and environmental com-
patibility in order for us to make the next evolutionary
step in engine development.

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