TwinForce squeezes V8 performance from a V6
Direct fuel injection and turbocharging have long been used in diesel engines for power and fuel economy.
Direct fuel injection and turbocharging have long been used in diesel engines for power and fuel economy. Ford Motor Co., Dearborn, Mich. (ford.com), is now taking that concept, calling it TwinForce, and using it in various consumer cars and trucks. Vehicles with a TwinForce Duratec 35 V6 engine should have 415 hp and 400 lb-ft of torque, numbers usually associated with a 6-liter V8. The TwinForce V6 would also get 15% better fuel economy than a similarly powered V8, according to Ford.
Compared to conventional port-fuel injection, TwinForce direct injection more precisely controls how much and when gas is sent into the cylinders. This means combustion is more efficient. Meanwhile, twin turbochargers deliver more air to the cylinders and boost power. It also reduces emissions and the engine can burn E-85 ethanol. The Ford says its new technology will be on future Ford and Lincoln vehicles.
Direct fuel injection and turbocharging have long been used in diesel engines for power and fuel economy. Ford Motor Co., Dearborn, Mich. (ford.com), is now taking that concept, calling it TwinForce, and using it in various consumer cars and trucks. Vehicles with a TwinForce Duratec 35 V6 engine should have 415 hp and 400 lb-ft of torque, numbers usually associated with a 6-liter V8. The TwinForce V6 would also get 15% better fuel economy than a similarly powered V8, according to Ford.
Compared to conventional port-fuel injection, TwinForce direct injection more precisely controls how much and when gas is sent into the cylinders. This means combustion is more efficient. Meanwhile, twin turbochargers deliver more air to the cylinders and boost power. It also reduces emissions and the engine can burn E-85 ethanol. The Ford says its new technology will be on future Ford and Lincoln vehicles.
Compression ignition comes to gas engines
What many consider the Holy Grail of combustion technology is one step closer to prime time.
In the race to field energy-efficient vehicles, don’t count out internal combustion technology just yet. GM recently debuted its homogeneous-charge-compression-ignition (HCCI) system in two drivable concept cars, a production-based 2007 Saturn Aura and Opel Vectra.
“HCCI was a dream of engine designers when I was an engineering student years ago,” says Tom Stephens, group vice president, GM Powertrain and Quality. “Today, using mathbased predictive analysis and other tools, we are beginning to make this technology real.“
HCCI is the capstone of an integrated suite of engine technologies that includes central direct-fuel injection, variable-valve lift, mechanical camshaft phasing, and individual cylinder pressure sensing. HCCI engines are said to use 15% less gas than conventional port-fuel injected engines, and meet current emissions standards.
Unlike spark-ignition gas engines or compression-ignition diesel engines that have a combustion process characterized by growth of a flame front from a single point in the combustion chamber, HCCI produces a flameless, simultaneous release of energy throughout the entire combustion chamber. Lack of a flame and hot zones lowers combustion temperature and NOx emissions.
Fuel-air mixtures are comparatively lean, which helps the engine approach the efficiency of a diesel, but without the need for costly lean-NOx after-treatment systems. Burning less fuel at lower temperatures also cuts the amount of heat energy lost during combustion, boosting efficiency. HCCI engines have a compression ratio of 12:1 (similar to that of a conventional direct-injected gas engine), so they can run on regular pump gas and E85. GM says HCCI engines will cost less to build than diesels because the latter need stronger components to withstand compression ratios greater than 20:1.
“Perhaps the biggest challenge of HCCI is controlling the combustion process,” says Uwe Grebe, executive director for GM Powertrain Advanced Engineering. “With spark ignition, you can adjust the timing and intensity of the spark. But with HCCI’s flameless combustion, you must change the mixture composition and temperature in a complex and timely manner to get comparable performance.”
Having ample heat in the combustion chambers is key to making HCCI work. The engines use a conventional spark ignition for cold starts and when HCCI is disengaged. Fuel comes from conventional injectors located in the center of each combustion chamber. A controller uses special algorithms and feedback from the cylinder pressure sensors to adjust cam timing and fuel injection in the milliseconds between combustion events. “Going to HCCI mode from conventional spark ignition signals the fast-mechanical cam phasers and a variable-valve-lift mechanism to close the exhaust valves early in the exhaust stroke, trapping some of the hot residual combustion gases in the combustion chamber,” explains GM Global HCCI Program Manager Matthias Alt. “This helps maintain a high cylinder temperature to facilitate auto-ignition when the fresh airfuel charge is added next cycle.” Operation at cold ambient temperatures necessitates trapping more hot gas in the combustion chamber (earlier exhaust-valve closing), for example.
Currently, the GM demonstration prototypes can run in HCCI mode to about 55 mph, going to spark ignition at higher vehicle speeds and under heavy engine load. A goal of the program is to extend HCCI’s operating envelope through refinements to the control system and engine hardware. GM says HCCI will work on any gasoline engine in its inventory and could combine with hybrid technology. No release date has been set for production HCCI-engine cars
Autonomous robotruck could save troops
Oshkosh Truck, Oshkosh, Wis., is introducing a 33-ft-long, autonomous robot truck that could transport weapons and supplies in combat and across dangerous roadways.
The Heavy Expanded Mobility Tactical Truck (HEMTT) A4, which charts its own course without human intervention, weighs 31 tons and can carry a 13-ton payload. It will debut next month at the Association of the U.S. Army annual convention, Oshkosh officials say.
The vehicle will perform such tasks as basic navigation, staying in the lane, and passing a static obstacle. The truck could also drive itself while a soldier rides along.
Oshkosh Truck, Oshkosh, Wis., is introducing a 33-ft-long, autonomous robot truck that could transport weapons and supplies in combat and across dangerous roadways.
The Heavy Expanded Mobility Tactical Truck (HEMTT) A4, which charts its own course without human intervention, weighs 31 tons and can carry a 13-ton payload. It will debut next month at the Association of the U.S. Army annual convention, Oshkosh officials say.
The vehicle will perform such tasks as basic navigation, staying in the lane, and passing a static obstacle. The truck could also drive itself while a soldier rides along.
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