Internal combustion engines will survive -- but automakers must wring from them all possible efficiency.
The pairing of internal combustion with hybrids and plug-in hybrids by all carmakers "is proof that internal combustion is here to stay for a long time," says Steve Ellis, manager of alternative-fuel vehicle sales and marketing at American Honda Motor Co. Inc.
The reason is fuel: For engines that run on gasoline, the fuel is generally inexpensive, plentiful and energy-rich compared to current alternatives.
Automakers are trying to make internal combustion engines more efficient -- reducing carbon dioxide emissions and fuel consumption -- without adapting expensive solutions and hurting that fun-to-drive feeling.
"We think customers will still require the same kind of performance that we have today, and we have to try to keep it all affordable as it competes against hybrids, etc.," says Dan Kapp, Ford's director of powertrain research and advanced engineering.
A key to boosting fuel economy is reducing the energy lost in a gallon of combusted gasoline.
Ben Knight, vice president of Honda R&D Americas Inc., says about 60 percent of the energy of combusted gasoline is now lost to heat. Writing in the Scientific American, Knight says about half of that loss is through the engine and half through the exhaust.
John Juriga, director of powertrains at Hyundai-Kia America Technical Center Inc., says electricity created from exhaust heat could be used to run electrically operated oil pumps and water pumps, for example. That would reduce engine drag and improve fuel efficiency.
Many automakers already use electric power steering to improve fuel economy as much as 2 percent.
"You don't have this mechanical pump that is always running and being a drain on the engine vs. taking an electrical motor and only using it when I need it," Juriga says.
Meanwhile, Ford is expected to add cooled exhaust gas recirculation to its EcoBoost engines during 2012 to 2017, Kapp says. The exhaust gas is captured and cooled in a heat exchanger, then pumped back into the cylinders, where it lowers the combustion temperature.
Kapp said the result is a cleaner-burning engine, an increased compression ratio and an increase in fuel economy of up to 5 percent compared with current EcoBoost engines.
Knight writes that an additional 15 to 25 percent of gasoline energy is lost to engine friction and to fuel consumed when the engine is idling or the car is decelerating.
This decade, U.S. automakers plan to install start-stop technology, which shuts off the car's engine when the vehicle is stopped and the driver applies the brakes. Releasing the brakes and touching the accelerator fires up the engine. Stop-start alone could boost fuel economy about 7 percent, according to some estimates.
Juriga says reducing engine friction -- which involves materials, parts design and lubricants -- has the potential to boost fuel economy 2 to 3 percent.
The remaining energy generated from combusted gasoline is engine output, Knight says. He estimates that one-half to two-thirds of that remaining energy is used to overcome vehicle weight, aerodynamic drag and rolling resistance created by the tires and the road. The rest is consumed by the drivetrain and accessories.
So is it possible to estimate how many years the internal combustion engine will be on the road?
Says Ellis: "If tomorrow there is some magic bullet, 100 percent of every vehicle sold was not internal combustion, you would still have internal combustion engines out there for the next 20, 25 years."