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Kia GDI engine

By Paul Clarke

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Kia GDI - Gasoline Direct Injection Engine

Kia has developed its own Gasoline Direct Injection engine which results in 10 percent better fuel economy and up to 12 percent more torque.

Based on the new Theta II family of units that will power the next generation of Kia vehicles, the GDI engine lowers emissions , improves fuel economy and raises power output.

One serious limitation of conventional fuel injection systems is that as engine revolutions increase, the valve opening and closing times get progressively shorter, thus reducing the time available to inject fuel. GDI avoids this problem altogether by positioning the fuel injector in the most optimal location, directly inside the combustion chamber to offer unparalleled precision. With this shorter and more direct path, far greater control is attained over the combustion process.

Split-injection technique

The injection is split into two phases to achieve optimum combustion: in the first phase, the pilot injection and ignition trigger the piston’s downward power stroke.  Then, in the main injection phase, during the piston’s descent, more fuel is injected and is ignited.


This split-injection technique reduces loading on the catalytic converter and helps lower emissions. This is particularly beneficial during cold starts when emissions are highest because the catalyst has not reached its optimal operating temperature. Split-injection enables the catalytic converter to reach the optimal operating temperature faster thus reducing emissions by 25 percent during cold starts and meet’s California Air Resources Board’s ULEV-2 and PZEV standards.

Fuel Economy

GDI’s other benefits include improved dynamic performance and better fuel economy . Compared to a conventional engine of the same displacement, GDI delivers 7 percent more torque at low revolutions and 12 percent more torque at the high-end for better take-off and overtaking performance. And a vehicle equipped with a GDI engine will get about 10 percent better fuel economy than a vehicle equipped with a conventional multi-point fuel injected engine .  Precise figures will vary according to the vehicle in which the engine is installed.

Developed at a cost of 170 billion won (£88 million) over a 46 month-long research period, the new 2.4 Theta II GDI engine will make its Korean debut in the first half of 2010. It is expected to appear in Kia products in the UK in 2011.

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