Fuel Efficiency Takes Baby Steps in the Auto Industry




Download PDF
Link to Original Publication

SAN FRANCISCO — Thanks to climate change policies and expensive gasoline, electric cars — and especially hybrid electrics — have made some inroads in the U.S. vehicle market. Still, the internal combustion engine is not about to go the way of the dodo. Mainstream engine makers are continually pushing forward incremental improvements and a few companies are developing radically different technologies.

Most of these innovators are still testing and marketing their designs and market barriers may slow or block widespread adoption, even if their inventions perform as hoped. Still, they say their technologies could deliver efficiency gains of as much as 55 percent.

The core of an internal combustion engine typically consists of an array of cylinders containing pistons linked to a crankshaft. Each piston is driven back and forth in a cycle of four phases, or strokes: intake, which pulls air into the engine; compression; combustion, in which fuel ignites and produces power; and exhaust. To improve upon the standard, engineers focus on making one or more of these steps more efficient.

Standard internal combustion engines are only 25 to 30 percent efficient, meaning they use only about a quarter of the fuel’s energy to power the car. Much of the rest is lost in heating the engine and exhaust, in friction and vibration of the moving parts or in air turbulence.

EcoMotors, from Allen Park, Michigan, seeks to increase efficiency by shutting down part of the engine when full power is not required. Many engine companies have been using this basic idea for some time, improving efficiency 5 to 6 percent by turning off cylinders when they are not needed. Still, even in off mode, although the pistons are not igniting fuel, they are still turning and generating friction, because they are connected to the crankshaft. The friction creates “a sizeable loss,” said EcoMotors’ chief executive Donald Runkle.

To avoid that, the EcoMotors innovative design “turns half of the engine totally off,” Mr. Runkle said.

Conventional engines combust fuel in the cylinder head. In EcoMotors’ engine, the pistons face each other, creating a combustion chamber between them, eliminating the need for a cylinder head. A few other companies use these “opposed-piston engines” as well, and the absence of the cylinder head and the elimination of many other parts makes them lighter and cheaper than conventional engines.

But EcoMotors real innovation is that by pairing the cylinders, it can stop piston motion in any pair without unbalancing the engine — unlike other engine designs that have to keep parts moving. This allows a modular architecture, stacking as many as three cylinder pairs, connected or disconnected with clutches, which can increase efficiency by 15 to 55 percent depending on the number of modules stacked, Mr. Runkle said.

Scuderi Group, in West Springfield, Massachusetts, aims to raise efficiency through a split-cycle design, dividing the four strokes between two cylinders: One handles intake and compression; the other combustion and exhaust.

This allows various energy savings. Separating compression from combustion allows the compression cylinder to be smaller, decreasing the energy required for the compression stroke. Also the timing of the valve movements and ignition can be improved. Instead of closing midway through the compression cycle when air is moving fast, which uses significant energy, the intake valve of the Scuderi motor’s compression cylinder can close at the bottom of the piston stroke, when “the velocity of the air is basically zero,” said the company president Sal Scuderi: and the transfer of precompressed air into the combustion cylinder allows efficient ignition timing relative to the motion of the power piston.

The company squeezes extra energy savings from an innovation it calls the air-hybrid, in which it stores energy as compressed air during braking and feeds it into the combustion cylinder when the car is accelerating.

Electric hybrids also use braking force to store energy – but in a battery. “We don’t have any of the disadvantages that batteries do: they’re very costly, they’re heavy, they’re hazardous waste, they wear out,” Mr. Scuderi said.

Another company, Sturman Industries, aims to improve efficiency by more tightly controlling the fuel burn. “Combustion happens in a thousandth of a second,” said Eddie Sturman, the technical director. “To control the combustion process, you have to have valves that work in millionths of a second.”

Sturman Industries, in Woodland Park, Colorado, has led industry moves to replace mechanical controls with sensor-guided electronics and hydraulics. Mr. Sturman won induction into NASA’s hall of fame in 2003 for a digital valve technology using electromagnetic coils controlled by electronic sensors.

The use of hydraulics further improves control over fuel injection by increasing the precision of the digital valves. “The power density of hydraulics is more than 30 times higher than that of any electric model,” said Mr. Sturman. “Power density gives us speed.”

Mr. Sturman hopes to raise engine efficiency 50 percent by using the same valve design to control air intake and exhaust, and fuel injection.

The three companies are in various stages on the path to market. EcoMotors has a licensing agreement with Navistar, which manufactures engines for commercial vehicles and electric generators. Mr. Runkle said it is also negotiating a licensing agreement with Zhongding, a Chinese company that manufactures engines for tractors, utility vehicles, and generators.

Scuderi has been testing its engine since 2009, and hopes to license its technology soon. “We’re in discussions with many companies in the automotive world and nonautomotive world,” said Mr. Scuderi, who is also considering the energy storage market, which could use its compressed air technology.

Sturman Industries is focusing on commercial diesel engines, including trucks and trains. It has manufactured 3,000 diesel fuel injectors and has also licensed Siemens as a manufacturer. It is considering additional licensing deals and also joint ventures.

“We’re going to demonstrate all the numbers and performance this year and be on commercial scale within two years,” Mr. Sturman said. Yet, even if these technologies prove themselves, experts say they may not revolutionize the mass engine market.

The New York Times automobile blogger Jim Motavalli says that mainstream vehicle manufacturers are steadily increasing efficiency by incorporating small innovations.

Danielle Fong, chief scientist at LightSail Energy, a Berkeley, California, company specializing in compressed air energy storage, agreed. “People go nuts trying to innovate in some kind of spectacular way,” Ms Fong said: “But even if it works, it’s so far behind” the gains coming from the gradual improvements in mainstream designs. “When you combine them, they actually do add up to something significant,” she said.

These birds in the hand are attractive from a policy perspective, said John Swanton, an air pollution specialist at California’s Air Resources Board. The board is counting on them to help reduce greenhouse gas emission from vehicles about 4 percent per year to meet its goals under the state’s 2006 Global Warming Solutions Act, he said.

“We have to adopt our regulations based on what the whole industry can do, cost effectively and reasonably, to get to the goals that we want in 2050,” Mr. Swanton said.

California reduced smog dramatically in recent decades by building on incremental changes stimulated by market competition, he noted. New technologies, he added, are more likely to win widespread acceptance if they draw on existing infrastructure and know-how.

“At the end of day, you don’t want anything too exotic,” Mr. Swanton said.