29 March 1999, Tokyo: Mitsubishi Motors Corporation announces the development of the GDI^*1 SIGMA Series powertrain, which marries the eco-friendly high-output low-consumption GDI engine with various peripheral technology such as CVT^*2, idling stop system, HEV^*3 and turbocharger. The GDI SIGMA Series powertrain returns mileage that is between 10% and 30% better than for current GDI engines, as well as realizing improved driveability and a reduction in cost.

In August 1996, the company became the first automobile manufacturer to apply gasoline direct injection technology^*4 in a production model. Today, GDI engines power eleven Mitsubishi Motors models, and the company plans to power all its models using this technology by the year 2010.

The company is currently developing other low-consumption technologies around the GDI engine. The first fruit of this program is the GDI SIGMA Series low-consumption powertrain, which incorporates four major technologies: (1)GDI-CVT, integrated control of GDI engine and CVT; (2)GDI-ASG^*5, idling stop system; (3) GDI-HEV, hybrid system; and, (4) GDI-GPT^*6, high-response, low-consumption GDI turbocharger. The company plans to start introducing the GDI SIGMA Series powertrain in its automobiles from the beginning of 2000.

GDI HEV (GDI SIGMA Series)

The shared perception In Japan and Europe today is that gasoline direct injection will be the core technology in next-generation gasoline engines and several auto manufacturers are currently working on its development. Mitsubishi Motors' GDI engine is attracting considerable attention for the following reasons:

1. Because it employs a vertical Tumble to control in-cylinder flow and transport fuel closer to the spark plug, thus realizing efficient combustion;
2. Because of Mitsubishi Motors' ongoing development of technology that meets more advanced requirements, and its continuing evolution of the GDI engine;
3. Because the melding together of combustion and exhaust gas after treatment technologies means compliance with the emission standards forecast in Japan and Europe for around 2010 is already well within sight;
4. Because it is a mature and proven technology, with over 500,000 GDI engines having been produced already.

1. GDI SIGMA Series: Technical Features

(1) Aim
The benefits of GDI engine include: Outstanding response; outstanding engine start; superior control of torque; less knocking, and less turbo lag. The GDI SIGMA Series powertrain has been developed to maximize the benefits and realize distinctly lower fuel consumption by synergizing these qualities with new drivetrain technology, auxiliary electric power equipment, new auxiliary equipment technology and performance-enhancing technology.

(2) System configuration
A variety of new technologies are under development in the GDI SIGMA Series program. On this occasion, Mitsubishi Motors is publishing details of the following four technologies:

1. GDI-CVT: Integrated control of GDI engine and CVT
2. GDI-ASG: Idling stop system
3. GDI-HEV: Hybrid system
4. GDI-GPT: High-response, low-consumption GDI turbocharger

2. GDI-CVT: Integrated control of GDI engine and CVT

(1) Aim
To integrate control of the GDI engine and CVT to realize a CVT that delivers outstanding low-consumption and driveability.

(2) CVT problems to date
The mating of a CVT to a conventional port-injection engine has traditionally been plagued by such problems as friction losses in the drive belts, internal losses in the torque converter; vibration in the vehicle body and low-fuel efficiency due to poor engine-transmission matching at low-consumption engine speeds.

(3) The solution
Integrated control of engine and transmission provides the solution to these problems, by maximizing the superior torque control and wider low-consumption speed range inherent to the GDI engine.

1. Hydraulic pressure is varied to match transmitted torque. The system reduces belt slippage during changes in hydraulic pressure by utilizing the GDI engine's inherent characteristics and limiting torque.
2. The system provides direct linkage-when there are no internal losses-over a wider speed range. By utilizing the GDI engine's inherent response characteristics to control top-end torque, the jerkiness resulting from torque differentials when the direct linkage disengages is eliminated.
3. The system matches control of top-end torque to the torsional frequency of the drivetrain to prevent resonance in the vehicle body.
4. At engine speeds of up to 1500 rpm- the common operating range for the CVT-the GDI engine's superior fuel consumption characteristics are maximized, realizing a significant improvement in fuel consumption.

Improvement in fuel consumption due to reduction in CVT operating pressure

3. GDI-ASG: Idling Stop System

(1) Aim
In the Japanese 10-15 urban use mode, idling accounts for 16% of fuel consumed in a multi port-injection engine and 10% in the GDI engine. The GDI-ASG system reduces fuel consumption by automatically turning the engine off while the vehicle is stationary. The system automatically restarts the engine when the driver operates the clutch and gear shift lever.

(2) Idling stop sytem problems to date
Idling stop systems have proved unpopular on port-injection engines because of the time the engine takes to restart, thus upsetting the driver's normal operation of the vehicle.

(3) The solution
Because the GDI engine injects gasoline directly into the cylinders, the engine starts faster. With GDI-Idling Stop System, the engine starts immediately, no matter how fast the driver operates the clutch and gearbox, thus enabling him to operate his vehicle in a totally natural manner.

Improvements to the alternator and its control system enable the reuse of kinetic energy generated during braking and deceleration, for improved fuel consumption.

Starting characteristics of GDI engine

4. GDI-HEV: Hybrid system

(1) Aim
Hybrid propulsion systems are high-efficiency, low fuel consumption technologies. However, the complex drivetrains, powerful electric motor/generator units and high-capacity batteries required make them very expensive. In the GDI-HEV, Mitsubishi Motors offers a simpler configuration that employs a small motor/generator unit and smaller batteries to reduce cost and thereby popularize the system.

(2) Hybrid system problems to date
Hybrid systems using port-injection engines have traditionally suffered from insufficient torque when moving off, and from jerkiness due to the engine cutting in and out. In addition, when driving on flat roads the limited amount of kinetic energy recoverable means that the engine generator must operate more frequently to supply the necessary power and this sees a rise in fuel consumption.

(3) The solution

1. The GDI engine's outstanding starting characteristics mean that motor torque is only required for 0.1 seconds when starting the engine. After that, engine torque assists vehicle acceleration.
2. In the GDI engine, the injection of even the smallest quantities of gasoline results in effective combustion. This makes it possible to minimize the amount of torque generated and thus the torque differential when the engine cuts in or out.
3. The GDI engine's excellent low-load fuel consumption enables the system to return outstanding fuel consumption even when the kinetic energy recovered during deceleration is insufficient and there is less low-load motor mode operation.

5. GDI-GPT: High-response, low-consumption GDI turbocharging

(1) Aim
To maximize the GDI engine's inherent characteristics and realize high-response, low-consumption turbocharging.

(2) Turbocharging problems to date
Turbocharging on conventional port-injection engines has traditionally suffered from such problems as: a lack of low- and mid-range torque due to knocking; increased fuel consumption because the compression ratio must be lowered to reduce knocking; and, turbo-lag in the initial stages of acceleration.

(3) The solution

1. Mitsubishi Motors' proprietary Two-Stage Mixing knocking control technology enables the use of a higher compression ratio, resulting in more low and mid-range torque.
2. The knocking control allows a higher compression ratio, and prevents an increase in fuel consumption. In addition, ultra-leanburn operation is possible over a wider speed range because the increased air supply due to the turbocharger enables the engine to support high-load operation under leanburn conditions.
3. Turbo lag is reduced because the turbine turns at very high speeds during leanburn operation before acceleration, when practically the same quantity of air is pumped through as when the turbine is turning at full speed.

Reduction in turbo-lag with GDI engine