Fuel Saving Engine Technology

Hydrogen Power
Hydrogen is one of the most exciting future fuels being examined by the auto and energy industries. Today, most major auto manufacturers have hydrogen fuel cell demonstration vehicles on the road. Hydrogen-powered internal combustion engine vehicles are also being tested. When used in a fuel cell, hydrogen is the ideal motor fuel because it creates electricity without combustion to power electric drive motors, with only heat and water vapor the byproducts. What keeps this a "future" fuel are the many unanswered questions facing hydrogen today, including how it can be affordably created, safely stored, conveniently distributed, and widely used. Hydrogen and the vehicles that run on this fuel currently provide an exciting window to our driving future, but they are probably decades away from mainstream use.

Pure Electric Vehicles
Battery electric vehicles have received plenty of attention over the past decade or so. These vehicles offer many advantages—such as zero localized emissions and the convenience of at-home recharging—but they also have significant challenges. Primary among these are insufficient driving range and high production costs, long recharging times (7 hours or so) largely due to the limitations of today's battery technology. Toyota has considerable experience with electric vehicles because of its RAV4 EV demonstration program that leased vehicles to fleets during the 1990s. Ultimately, even with technologically advanced vehicles capable of running seamlessly on electric power, battery limitations have relegated full-function pure electric vehicles—at least for now—to an historical footnote.

Hybrid Vehicles
The trails that battery electric vehicles blazed have helped contribute to the development of the hybrid-electric vehicles we see on American roads today. While much of the excitement surrounding hybrids is well earned, it's important to note that not all hybrids are created equal, and important distinctions are to be made between the various hybrid systems currently on the market or soon to be released.


First, the definitions: A series hybrid is driven exclusively by one or more electric motors, with the internal combustion engine's sole purpose that of generating electricity for powering the motors. There are currently no automobiles with a series hybrid system on the market. A parallel hybrid typically uses an internal combustion engine for most of its propulsion, relying on an electric motor for boosts of acceleration. There are variations on these two themes as well as amalgamations that result in "hybrid" hybrid powerplants, which blend a bit of both configurations into a single unit.


"Mild" hybrid systems are beginning to emerge that achieve modest fuel economy increases. These systems typically use an idle-stop feature that shuts an engine off while a vehicle is stopped, and a motor-generator that automatically starts the engine and provides initial propulsion as the vehicle starts up again. Like their full hybrid counterparts, mild hybrids use regenerative braking to capture energy as a vehicle decelerates, allowing the generator to feed some electricity back to the vehicle's batteries. The mild hybrid's advantage is that it is a relatively simple and affordable design. Its drawback is that it does not provide the kind of spectacular fuel economy improvements.