The internal combustion engine, a technology that is over 100 years old, will keep powering most automobiles for a while--at least for the foreseeable future which will see more green technology fuel cell or electric care domination.
Engineers are finding ways to wring more efficiency and performance out of combustion engines. Let's run down the list.
Cylinder/Motor Deactivation
Cylinder-deactivation, in which the motor cuts out two or more cylinders when the car is in cruising mode, is one such improvement. And General Motors, Chrysler and Honda Motor are already selling vehicles with cylinder deactivation.
Similarly, start-stop technology--shutting off the engine while the car is idling--can reduce fuel consumption by as much as 10%. This technology, integral to hybrid vehicles.
Direct Injection
Another present-day fuel-saving technology is direct injection, which delivers fuel directly into the combustion chamber of each cylinder, rather than into the intake manifold.
Siemens VDO (now part of Continental AG of Germany) claims that its direct injection system can deliver fuel savings of up to 20%.
Smaller Displacement Motors
Except when charging up a hill or trying to merge onto a freeway ramp, most vehicles need only a fraction of the motor's maximum power. Smaller and lighter engines offer multiple advantages: lower friction losses and weight-savings on the surrounding body structure and suspension.
By utilizing less space under the hood--replacing a six-cylinder with a four-cylinder, making it aerodynamic.
Another way to get a four-cylinder to perform like a six- or even eight-cylinder is with forced induction--pushing more air into the combustion chamber--via a supercharger or turbocharger.
Diesel
In the urgent quest for fuel efficiency is the diesel engine, quite popular in passenger cars in Europe.
Diesels have advantages in fuel economy, extended driving range and durability. The diesel also delivers healthy levels of torque relative to its size and displacement.
The problem: controlling particulate emissions, engine clatter and cost.
Leveraging the Motor
In addition switching to lighter-weight materials, converting to low-power, light-emitting diodes and replacing mechanical systems, such as steering and throttle linkages, with "by-wire" electrical controls can add as much as 3% fuel efficiency.