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4x4 Hybrid Vehicle Engines - Engines Au Juice

Energy Monitor
Ken Brubaker
| Senior Editor, Four Wheeler
Posted January 1, 2005
Photographers: The Manufacturers

Is There A Hybrid In Your Future?

By now you've heard the term "hybrid" bandied about ad nauseum. Well, the fact is that you will probably hear it a lot more over the next few months and years, because hybrids are infiltrating the four-wheel-drive world faster than you can say, "high-power battery module." To fully understand what a hybrid-powered vehicle can or can't do for you, you must have a basic understanding of what makes 'em tick-or, more appropriately, what makes 'em hum.

First off, it's important to note that hybrid systems are extremely complex, often integrating multiple electronic control units. To further muddy the waters, each manufacturer has approached the design and operation of its specific hybrid system differently. To explain the detailed workings of each hybrid from each manufacturer would take far more pages than we have, so we'll highlight the basic technology of a few specific vehicles that are currently available.

First, the term hybrid is a catchall phrase. The reality is that there are two basic types of hybrids, and on the street they've come to be known as full and mild. A full hybrid is defined as a vehicle that sports a gasoline or a diesel internal combustion engine (ICE) and at least one electric drive motor. Full hybrids are capable of operating in gas or electric modes as well as in a mode that combines the power of the ICE and electric motor. Some full hybrids also include other electric motors that drive a second pair of wheels or serve a specific duty unrelated to direct propulsion. Further, these electric motors can vary in their activation time as well as in how much power they produce. Why would a vehicle need two sources of power? The answer is that most full-hybrid vehicles that are designed for fuel efficiency rely on small and fuel-efficient ICEs that lack performance. When the power of the ICE and electric motor are combined, performance is enhanced, delivering the best of both worlds. Full hybrids can produce almost double the fuel economy of a comparable gasoline-powered vehicle and they significantly reduce tailpipe emissions because many are low-emission ICEs and they're shut off often. Mild hybrids, on the other hand, don't utilize an electric motor to assist the ICE. Instead, they increase fuel mileage mainly by shutting down the ICE when the vehicle is stopped or decelerating. The rest of the time the engine runs normally. This design generally produces fuel economy increases of 10 to 15 percent.

Both types of hybrids forced engineers to think outside their usual cubicles during research and development. For instance, when an ICE shuts down, there is no power to spin pulleys and belts. Since hybrids shut down the engine often, engineers had to find a way to run items like the power-steering pump, air-conditioning compressor and the water pump. With the exception of the alternator, which is replaced by the electric motors integral to a hybrid, these problems were solved creatively. Take steering, for example. Many manufacturers utilized an electric pump to move the power-steering fluid. Transmissions were another sticking point. Some manufacturers began using a constantly variable transmission (CVT), while others merely added an electric pump to a standard automatic transmission. A by-product of eliminating these beltdriven items is that there are fewer items for the engine to power, thus improving fuel consumption.

So, is there a hybrid-powered 4x4 in your future? Will the hum of an electric motor soon replace the grumble of an internal-combustion engine as you creep along your favorite trail? Will you soon be shopping the aftermarket for upgraded battery systems? Will you be drooling over electric motor hop-up kits? It's likely, and it may happen sooner than you think. Read on.

It's not often you'll see a car on the pages of Four Wheeler, but this car is important to this story. After all, the Toyota Prius is arguably the hybrid that started it all. Sure, the Honda Insight was introduced in the United States a year before the Prius appeared, but to this day, the Prius remains the most popular of all hybrids. The Prius is a full hybrid that sports a 1.5L four-cylinder gasoline engine that produces 76 hp and 82 lb-ft of torque. The engine is mated to a permanent-magnet electric drive motor that produces 67 hp and 295 lb-ft of torque. Nickel-metal hydride batteries comprise the battery system. The Prius also features a continuously variable transmission.

Driving the Prius is a trip. First off, there's no reason to use the key to unlock and start the vehicle because the optional smart entry and start system senses a key fob you carry on your person, unlocks the doors when you tug on the handle and allows you to start the car using a PlayStation-like power button. If the ICE is cold it will start, but if it's warm, it may stay off. This is why the dash features a ready light that illuminates when the car is ready to drive. Gear selection is done via a small joystick mounted on the dash. It's an electronically controlled by-wire shift system, so it just takes a tap of the finger to shift. Acceleration is smooth and seamless via a by-wire throttle. As you drive, you can monitor electric-gas power distribution through the Hybrid Synergy Drive system on the standard 7-inch touch-panel display monitor.

The Prius usually runs on the ICE during highway driving. The electric motor propels the car at low speeds. Occasionally, both may team up to produce maximum power. We were amazed at how seamless the system is. Our testing returned a 41-mpg average in rural driving. We have a friend who drives a Prius in L.A. traffic regularly and reports a 51-mpg average.

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