Hyundai Says Its First GDI Engine Achieves 35 MPG Highway in 2011 SonataBy Scott Doggett November 23, 2009
The 2011 Hyundai Sonata that'll appear in U.S. showrooms starting early next year will feature the South Korean automaker's first gasoline direct-injection engine, a totally revamped 2.4-liter Theta engine that achieves 35 miles per gallon on the highway, Hyundai reported Monday.
Company officials said the engine, a four-cylinder built at Hyundai's Alabama plant, also creates fewer greenhouse-gas emissions and delivers improved throttle response in addition to being about 10 percent more fuel efficient than the 2.4-liter engine in the current Sonata.
Hyundai Motor America President and CEO John Krafcik said in a statement that "the introduction of this technology in our most important, highest volume product ... demonstrates our commitment to delivering products that excite and reward Hyundai owners."
Hyundai's Theta I-4 engine family is a proprietary design engineered in Namyang, Korea, and currently produced at volumes exceeding 2 million units annually. The new Theta II 2.4-liter GDI engine delivers 200 horsepower at 6,300 rpm and 186 pound-feet of torque at 4,250 rpm.
Hyundai says its direct-injection engine is different from all others in that it uses individual fuel injectors for each cylinder "strategically positioned to deliver the optimal fuel charge directly into the combustion chamber."
In a traditional multi-port system, gasoline is delivered via the port of each cylinder, where it mixes with air and is drawn into the cylinders when the intake valve opens and the piston moves down. A drawback to that system is when engine speeds increase, the time to open the valve to deliver fuel becomes progressively shorter, making accurate delivery more challenging.
Hyundai says its GDI system avoids that issue by injecting gasoline by a camshaft-driven pump that operates at pressures up to 2,175 pounds per square inch. The pistons are "domed" to increase combustion efficiency.
The injection is split into two phases to achieve optimum combustion during the catalyst heating operation right after the cold start. First, the pilot injection is applied during the piston's descent in the intake stroke and then, in the second, at the end of the compression stroke, the rest of the fuel is injected and then ignited after some delay.
This split-injection technique reduces loading on the catalytic converter and helps lower emissions, Hyundai says.
Moreover, when an engine is cold, so is the catalyst. Traditional engines run high rpm's for a few seconds upon startup to "fire" the catalysts.
The GDI's split-injection strategy enables the catalyst to reach operating temperature faster. This helps reduce emissions by 30 percent during cold starts meeting California Air Resources Board's ULEV-2 and PZEV standards.
Compared to a conventional engine of the same displacement, GDI delivers 7 percent more torque at low engine rpm's and 12 percent more torque at the high-end for better take-off and overtaking performance. Best of all, GDI boosts gas mileage by up to 10 percent compared to a conventional engine.