The Pistachio
In August 1996, Mitsubishi Motors became the first company to use a Gasoline Direct Injection engine to power a production model - since then cumulative production has topped 700,000 units. The new sub-compact Pistachio is powered by an Automatic Stop/Go component version of Mitsubishi's GDI SIGMA Series powertrain. With GDI-ASG, and a vehicle weight reduced to under 1000 kg, the Pistachio realizes a dramatic improvement in fuel efficiency, returning the amazing mileage for a 'litre' car of 3.3 litres/100km in the Japanese 10-15 urban driving cycle. This is said by Mitsubishi to be a world first for a vehicle fuelled only by petrol.
(And if you're thinking - "Pistachio!?" WTF? Here is Mitsubishi's rationale for naming a car after a nut: "The pale green colour and the brittle sound the shell makes when opened conjures up an image of the environment, nature and clean emissions." Now you know!)
Used in the Pistachio is the brand-new 4A31-type 1100cc in-line 4-cylinder Gasoline Direct Injection engine. The smallest of its type in production, the 4A31 engine develops 54kW at 6000 rpm and 100Nm of torque at 4000 rpm. The DOHC 16-valve engine uses a very long stroke design - stroke is 80mm with a bore of only 66mm. The stratified charge direct injection system allows a very high compression ratio (in this case 11:1) to be used without detonation problems.
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10-15 Urban Driving Cycle?
The 10-15 Urban Driving Cycle is a Japanese industry standard that measures the mileage and the amount of exhaust gas produced by a petrol-powered vehicle in urban driving. A set program of accelerations, constant running and decelerations for given durations of time and at set speeds, including engine idling, 20 km/h, 40 km/h, 50 km/h, 60 km/h and 70 km/h make up the urban driving model.
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Automatic Stop/Go
In the Japanese 10-15 urban driving cycle, idling accounts for 15 per cent of the total fuel consumption for a conventional engine and 10 per cent for the GDI engine (as measured by the Japanese Ministry of Transport). Thus stopping the engine when it would otherwise be idling will produce significant savings in fuel consumption. With conventional engines, however, the uneasiness the driver experiences due to the delay before his/her engine restarts - and other problems - still need to be overcome.
The GDI-ASG system is said to solve these problems with the Automatic Stop/Go control system - a simple clutch pedal-operated engine restart system - and the superior starting characteristics of the GDI engine. As a result, all the driver has to do to restart the engine after the ASG system has stopped it at idling (only when the vehicle is at rest, the shift lever is in neutral and the clutch is engaged) is to disengage the clutch by pressing the clutch pedal. The lack of any complicated restarting procedure, and the very fast engine restart - a fraction of the time required of a conventional engine - eliminates worries about increases in emissions or about holding up other vehicles in traffic due to being slow to move off again.
The GDI engine starts and restarts faster than conventional engines because petrol is injected directly into the cylinder late in the compression stroke. The GDI's first combustion occurs at 1/6th of a revolution after the fuel is injected, compared to 1-1.5revolutions for conventional engines. Fears of stalling are thus banished, and the quantities of electricity and fuel needed to start the engine are reduced.
The GDI-ASG also employs a brake energy regeneration system to store kinetic energy released during braking, and uses the energy to assist the alternator when the engine is restarted. There is a positive environmental impact as well. The CDI-ASG starts quickly, so CO2 concentrations in the exhaust are lower than those for conventional engines.
The Results
The Japanese market only Pistachio makes the most of the GDI-ASG combination. This compact vehicle would naturally be fuel-efficient, weighing in as it does at 700kg. But powered by the GDI engine married with Mitsubishi's ASG technology, the Pistachio achieves extremely low fuel consumption.
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Mitsubishi‘s GDI Usage
Mitsubishi Motors became the first auto manufacturer to develop the GDI engine for practical use. It has now built more than 700,000 of them. Mitsubishi Motors is convinced that engines incorporating GDI technology will provide the main source of propulsion for passenger cars at the beginning of the 21st century. To this end, the company is focused on promoting the widespread use of this type of engine by increasing the number of GDI-powered production models.
The Proudia and Dignity is powered by 4.5-litre V8 GDI engine (206kW at just 5000 rpm and a massive 412Nm at 4000 rpm), the Pistachio with the 1.1-litre in-line 4-cylinder GDI engine and the Dion powered by the newly developed 2.0-litre GDI engine. Together with other models, starting with the Galant and Legnum series launched in August 1996, a total of 15 Mitsubishi domestic market model series currently use this power unit. Many of these models clear the 2010 fuel consumption requirements and the Pajero, Proudia, Dignity and Dion all comply with the Japanese 2000 Emissions Regulations, realizing not only a major reduction in CO2 but also substantially lowering the output of carbon monoxide, hydrocarbons and NOx emissions as well. Outside of Japan, in October 1997 Mitsubishi Motors launched the 1.8-litre GDI Carisma produced at NedCar, the company's manufacturing unit in the Netherlands. This has since been followed by GDI-powered Volvo S40 / V40 and Mitsubishi Space Star models, which are also produced at the NedCar plant. The company also exports GDI-powered Galant and Space Wagon (Chariot Grandis in Japan) to Europe. The GDI Engine also powers the Pajero Pinin produced by Industrie Pininfarina S.p.A in Italy from July 1999. The company is supplying GDI engine technology to Peugeot SA of France and Hyundai Motor Co of Korea. In Australia our relatively poor fuel has meant that local testing of GDI engines has so far resulted in poor performance and emissions gains.
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