GM, Porsche and BMW are among the automakers announcing gasoline direct injection (GDI) engines in new models introduced at the North American International Auto Show in Detroit. Gasoline direct injection technology offers improved combustion and fuel efficiency, offering automakers either a way to deliver comparable power with lower fuel consumption, or increased power with less of a fuel consumption penalty.
Direct injection delivers precisely metered and timed fuel directly to the combustion chamber, enabling a more precise mixture formation. This also has a cooling effect in the chamber, enabling a higher compression ratio, and improving engine efficiency. Less fuel is required to produce the equivalent horsepower of a conventional port injection combustion system.
GM introduced its new 3.6-liter direct injection engine—first announced in May 2006—as the top-level engine for its new 2008 Cadillac CTS. The V-6 engine with variable valve timing (VVT) delivers an estimated 223 kW (300 hp) of power and 366 Nm (270 lb-ft) of torque. Designed to operate with regular unleaded gasoline, the new 3.6-liter direct-injection V-6 produces power similar to many V8 engines, but with better fuel economy.
The new engine delivers a 15% increase in horsepower; an 8% increase in torque, and a 3% improvement in fuel consumption compared to its predecessor. Additionally, the application of direct injection reduces cold-start hydrocarbon emissions by 25%.
This is GM’s third engine with gasoline direct injection. In 2006, the company also announced an Ecotec 2.0-liter four-cylinder Turbo engine with direct injection on the 2007 Saturn Sky Red Line and Pontiac Solstice GXP roadsters. A naturally aspirated Ecotec 2.2-liter direct injection engine has been offered on Opel models in Europe since 2004.
BMW, which announced a new in-line six-cylinder, 3.0-liter bi-turbo gasoline engine with direct injection (High Precision Injection) and fully variable camshaft control to optimize combustion in March 2006 (earlier post), announced its first four-cylinder, 2.0-liter gasoline direct injection engine, to be applied in its newly announced 320i Convertible.
One version of the earlier-announced 3.0-liter with High Precision Injection (HPI), applied in the new BMW 330i Convertible, delivers 200 kW (272 hp) with peak torque of 320 Nm (236 lb-ft). Average fuel consumption under the EU standard is 8.1 liters/100 kilometers (29.0 mpg US). Another version of the 3.0-liter straight six, applied in the 325i Convertible, develops maximum output of 160 kW (218 hp) and peak torque of 270 Nm (199 lb-ft), with fuel consumption of 7.9 liters/100 km (29.7 mpg US).
The new 2.0-liter HPI engine develops maximum output of 125 kW (170 hp) and peak torque of 205 Nm (151 lb-ft). This first representative of the new generation of four-cylinder power units combines gasoline direct injection through centrally arranged piezo injectors with infinite, fully automatic adjustment of the double-VANOS intake and outlet camshafts as well as the flexible DISA intake system switching to the right operating mode at all times. Average fuel consumption in the EU test cycle is 6.7 liters/100 kilometers (35.0 mpg US).
Porsche introduced its first GDI units with three new engines for its newly introduced second generation of the Cayenne family. For the high-end 2008 Porsche Cayenne Turbo, that means a twin-turbocharged 4.8-liter V8 that produces 500 hp (373 kW) and 516 lb-ft (700 Nm) of torque. Combined with a six-speed transmission, the turbo SUV accelerates from 0 to 60 mph in 4.9 seconds and has a top speed of 171 mph (275 km/h).
However, the direct injection technology enables an improvement in fuel efficiency of up to 11% in highway driving compared to the previous generation Cayenne Turbo. Estimated EPA fuel economy values for the new Cayenne Turbo are 13 mpg for city driving and 20 mpg on the highway.
The 2008 Porsche Cayenne S uses a normally aspirated version of the 4.8-liter V8 that generates 385 hp (287 kW) and 369 lb-ft (500 Nm) of torque. The Cayenne S V8 even meets ULEV (ultra low-emission vehicle) status and according to preliminary testing data offers 14 mpg in the city and 21 on the highway. That is an improvement of 3 mpg or around 15% for highway fuel economy.
Finally, the entry-level Cayenne is powered by a 3.6-liter V6 that produces out 290 hp (216 kW) and 283 lb-ft (383 Nm) of torque. The new Cayenne gains LEVII emission status and preliminary fuel economy testing showed estimated EPA fuel economy figures of 18 mpg in the city and 22 on the highway. That is a fuel economy improvement of 3 mpg for city driving.
In addition to direct injection, the 2008 Porsche Cayenne S and 2008 Cayenne Turbo’s 4.8-liter V8 features VarioCam Plus valve control, a technology that enhances performance through infinite valve timing and valve lift adjustment on the intake side.