ototake rally pajero development 2004

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In mid-2001, the rules of the Dakar Rally, which had

until then limit ed entry to modi fied production models

(T2-class), were revised to make completely new proto-

type four-wheel-drive (4WD) vehicles eligible to take

part. Taking advantage of the freedom y ielded by the

new rules, Mitsubishi M otors Corporation (MMC) devel-

oped a new-concept cross-country rally car, the

PAJERO EVOLUTION, with a v iew to securing victory in

the 2003 Dakar Rally . Two PAJERO EVOLUTIONs tookpart in 2003, one crossing the fin ishing l ine in fi rst place,

the other in thi rd place (Fig. 1). A technical overv iew of

the PAJERO EVOLUTION is given in this paper.

1. The Dakar Rally

The competition now known as the Dakar Rally f irst

took p lace 25 years ago (in 1979) and i s renow ned as

the longest and toughest rally in the wor ld. Starting in

mid winter, participants race from Europe into Africa,

where they experience mountains, rocky roads, dirt

tracks, deserts, sand dunes, savanna, and other chal-

lenging terrain over a period of about t hree weeks anda total di stance of about 10,000 km.

MMC has entered PAJEROs every year since 1983

(the year after the first-generation PAJERO was

launched). In this 20-year period, MM C has achieved

eight victories, including three consecutive victories in

the last th ree years.

2. Concepts behind new PAJERO rally car

2.1 Vehicle classification

The minimum mass of a competing vehicle is deter-

mined i n accordance with the engine’s swept volum e

as shown in Table 1.

2.2 New PAJERO EVOLUTION rally car (Fig. 2)

Taking advantage of its existing technological base,

MMC gave the new PAJERO EVOLUTION superior com-

petitive strength and reliability using the following fea-

tures:

• Reposit ioned drivetrain (yielding a lower center of

gravity)

• Lightweight, high-rigidity tubular frame

• Four-wheel independent suspension (superior in

terms of both handling stability and roadholding)

combined with a long wheelbase (superior in termsof dynamic stability and load capacity)

• Newly tuned version of the previous model’s proven

engine

3. Engine specifications

The Dakar Rally r ules permi t competing v ehicles tobe powered by either gasoline engines or diesel

Development of PAJERO EVOLUTION Rally Car

for 2003 Dakar Rally

Yoshihiko OTOTAKE* Shuusuke INAGAKI*

* Motor Sports Team, Research & Development Office

Fig. 1 PAJERO EVOLUTION rally car at 2003 Dakar Rally

finishing line

Table 1 Minimum vehicle mass by engine swept volume

Engine sw ept volume (cc) 4W D vehicle (kg) 2W D vehicle (kg)Smaller than 1,600 1,300 920

1,600 – 2,000 1,525 1,040

2,000 – 2,500 1,600 1,100

2,500 – 3,000 1,675 1,160

3,000 – 3,500 1,750 1,220

3,500 – 4,000 1,825 1,280

4,000 – 4,500 1,900 1,340

4,500 – 5,000 1,975 1,400

5,000 – 5,500 2,050 1,460

5,500 – 6,000 2,125 1,520

6,000 – 6,500 2,200 1,580

6,500 – 7,000 2,275 1,640

7,000 – 7,500 2,350 1,700

7,500 – 8,000 2,425 1,760

Larger than 8,000 2,500 1,820



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Development of PAJERO EVOLUTION Rally Car for 2003 Dakar Rally

engines. Turbochargers are forbi dden for gasolin e

engines but not for di esel engines. Each engin e may

have a maxi mu m com pression ratio of 10.5 and must

have a restrictor to lim it the rate of air intake (A 32 mm-

diameter restrictor is mandatory for a four-valve-per-

cylinder engine).

The PAJERO EVOLUTION is powered by an upgrad-

ed version of the proven 6G74 MIVEC engine.

Enhanced torque characteristics yield stronger low -end

torque and a flatter torque curve, and the engine is

ligh ter than the origi nal version. Also, an upgraded

cooling system w ith increased radiator and oil-cooler

capacities better enables the engine to w ithstand low -

speed, high-load operation for long periods.

4. Drivetrain (Fig. 3)

In line wi th the revised rules, MM C lowered the vehi-

cle’s center of gravity by repositioning the front di ffer-

ential in front o f the engine (thereby flattening the pro-

file of t he engine-and-transmi ssion assembl y) and by

lowering the engine-and-transmission assembly’ s posi-tion. The full-time 4WD drivetrain has viscous coupling

units (VCUs) for the center and front d ifferentials and a

mechanical lim ited-slip d ifferential for the rear differen-

tial to ensure superior traction and reliability. A locking

mechanism was added to the front-differential VCU

(positioned in parallel with it) to aid extrication of the

vehicle from sand dunes. With the transmission, a six-

speed sequential shift mechanism was adopted to

enable easy shifting. As a way to reconcile the need for

a lower center of gr avity with the conflicting need for

increased ground clearance, MM C redesigned the entire

drivetrain to enable large, weighty components to be

arranged on a relatively flat profile over the botto m o f

the vehicle. Jum ps and other rally maneuvers create

frequent shock inputs that h ave the potential to cause

drivetrain damage. Since the drivetrain of the PAJERO

EVOLUTION rally car was built using n ewly specified

components, the likelihood of such damage was

deemed too difficult to predict. A torque limiter was

thus employed to mitig ate shock inputs. The torque

limiter is based on a standard clutch mechanism and

incorporates modifi cations for an opti mal combi nation

of slip-speed characteristics and therm al characteristics.

In the drivetrain, the torque lim iter is arranged in series

wi th a standard clutch. The torqu e lim iter and clutchproved successful in preventing sudden breakage of dri -

vetrain parts, but the torque limiter was found to require

careful w ear m anagement.

Fig. 2 Key features of new PAJERO EVOLUTION rally car



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Development of PAJERO EVOLUTION Rally Car for 2003 Dakar Rally

7. Summary

Two d ecades of conti nual experience in t he Dakar

Rally and i ts predecessors since the introduction of t he

first-generation PAJERO have given MM C a wealth of

knowledge on w ays to maximi ze vehicle perform ance

and reliability under long-distance, off-road conditions.

By applying this knowledge to production vehicles,

MMC has successfully evolved the PAJERO in terms of

speed, reliability, safety, and comfort. As MMC contin-

ues to develop technologies for victory under harsh

African rally conditions, it will continue to reflect the

benefits not only in production PAJERO models but also

in all other M itsubishi vehicles.

Yoshihiko OTOTAKE Shuusuke INAGAKI

ototake rally pajero development 2004

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