FRANKFURT - Mitsubishi engineers redesigned their GDI engine for Europe and the 1998 Carisma. The European version of its gasoline direct-injection engine will be introduced at the Frankfurt auto show in September.
While the Japanese engine was tuned to give the best fuel savings at idle speeds, the European version is tuned to save fuel on the highway.
The GDI engine gives up to 25 percent better fuel economy than the current 1.8-liter engine in the Carisma, has very high low end torque, and delivers 125ps.
'The Euro-GDI is completely different from the Japanese GDI for the 1997 Galant,' said Akira Kijima, general manager of Mitsubishi Motors' corporate engine r&d department.
Kijima offered the first public information on details of the Euro GDI.
'The Euro GDI has been customized for European driving conditions and tastes,' he said. 'The changeover point from lean (40: 1) to normal (14.5: 1) air-fuel mixture has been raised from 2,000 to 3,000rpm. So speed in the lean range is extended to rolling along a highway at 120-130kph.'
The Japanese engine was tuned to save as much as 30 percent at idle speeds, but it saved little at highway speeds.
Controlling NOx emissions in lean-burn engines has been a challenge, but the Euro GDI is well below current EU standards, set in 1993.
The iridium catalyst works in combination with an exhaust gas recirculation valve that returns up to 30 percent of exhaust fumes to the intake manifold.
However, the EU's targets for 2000 will be difficult to meet.
'We are working with high intensity, to comply to this very stringent mode. The trouble is sulfur. It poisons catalysts,' said Kijima. 'European gasoline contains up to five times more sulfur than Japanese fuel. US fuel is even worse. Our specially developed tandem catalyst stands up to sulfur but it is not sufficient for EU mode 3.'
In Mitsubishi's dual-catalyst system, the first catalyst uses pure iridium. It works during the lean period. A normal platinum catalyst is mounted behind it, to clean up exhaust created during non-lean periods.
EU mode 3 is a problem because at present there is no anti-NOx catalyst with sufficient conversion capacity for lean-mixture driving that will stand up to sulfur, said Kijima.
Changes for Europe
Mitsubishi made several significant changes to its GDI engine to tune it for Europe:
The angle of the injector in the combustion chamber is steeper. The injected fuel is forced to travel a greater distance while being mixed more intensively with the vertical tumbling airflow
To get better low end torque, the intake manifold was extended from 265mm to 400 mm. The timing of injection and ignition was changed for the lean cycle. In dual injection, a small amount of fuel is injected during the intake stroke for stratification, while during the following compression stroke a larger amount of gasoline is injected to build up a layer of rich, ignitable mixture around the spark plug
The compression ratio was raised from 12: 1 to 12.5: 1
The iridium catalyst was improved.
With the Euro GDI engine, low-end torque at 800rpm is 55 percent higher than with the normal 1.8-liter engine in the current Carisma. At 1,500rpm, torque is 9 percent higher. Power output is reduced from 150ps to 126ps.
Kijima said GDI costs $300 per unit more than a normal engine.
Mitsubishi recently announced that it was developing a 3.5-liter, V-6 GDI in Japan for new models and the Pajero.
Also, there are indications that Mitsubishi is working on a 660cc GDI for minicars.