Gasoline, Electricity … or Both

Advanced hybrid powertrain technology makes high gasoline prices a little more palatable.

Many consider the 1950s and 1960s to be the heyday of the American auto industry. There was no foreign competition, and America was brimming with optimism. The cars of the day were stylish and powerful and no one worried about fuel economy, air pollution or global warming. Each year brought styling and design changes to entice the buying public.

Let’s fast forward to 2008. The purpose of the automobile remains basically the same today as it was 50 years ago: To provide transportation from one point to another. But, there are some strings attached. The Federal government stepped into the picture in the early 1970s and began to dictate emissions levels, then fuel economy standards. This intervention has increased over the years to the point that all automakers must achieve an overall fleet fuel economy standard of 35 mpg in 2020.

The innovations that automakers have developed over the last 35 years to meet Federal standards and reduce tailpipe emissions and fuel consumption have been nothing short of amazing. Of course, this technology includes the widespread use of electronics and computers. In order to continue this technological stampede, hybrid powertrains have been thrown into the mix.

HYBRID BASICS

Basically, a hybrid vehicle has two power sources that are both used to maximize the overall performance of the powerplant. There are two types of hybrid vehicles. One is the series hybrid in which one power source is not connected directly to the transmission of the vehicle. It is used to supply power to the other power source. One of the most common types of series hybrid vehicles is the diesel railroad locomotive. In simple terms, a diesel engine powers a generator that supplies current to electric motors located between the wheels of the locomotive. It’s these electric motors that propel the train.

The second type of hybrid vehicle is the parallel hybrid in which two power sources are both connected to the transmission. Each power source is used independently, or sometimes together, to drive the vehicle. The hybrid automobiles that you’ve seen on the road this past decade are essentially parallel hybrid vehicles, utilizing an electric motor and a gasoline-powered internal combustion engine.

The electric hybrid vehicle is a cross between an electric car and the gasoline car. Electric cars have been around for decades. Such a car is quiet, powerful and clean. But the major drawback has always been range. Battery technology still does not exist that provides comparable range to the gasoline car. Therefore, electric vehicles have seen limited widespread use.

But what if you could use both power sources in one vehicle, taking advantage of the positives of each? That’s what has been done in the hybrid electric vehicle. The net result is a vehicle that has comparable performance to the gasoline powered car, with significant gains in fuel mileage and reductions in tailpipe emissions. The best of both worlds.

Each hybrid vehicle on the road (and there are many from several manufacturers) operate basically the same, but there are differences from model-to-model. Let’s look at the simplified operation of a typical hybrid electric vehicle. When you get in the car and turn the key, the electric motor turns on, not the gasoline engine. As you accelerate, it is the electric motor that is moving the vehicle. Once you reach a certain speed, the gasoline engine either assists the electric motor, or takes over completely. At highway speeds, it is usually the gasoline engine providing the power. The electric motor is used occasionally to provide additional power for passing and climbing grades.

You’re probably wondering how the batteries for the electric motor are recharged. This is accomplished by a concept known as regenerative braking. In addition to using the brakes to slow down and stop the car, the electric motor is used as a generator to recharge the batteries. So if you’re driving all day in city traffic, you won’t use the gasoline engine a lot and your city mileage will be better than your highway driving mileage.

THE CHRYSLER HYBRID

All this talk about hybrid technology really wouldn’t mean much unless Chrysler was a player in the hybrid game. Well, they are. In November, 2007, Chrysler LLC announced the all-new 2009 Chrysler Aspen HEMI® Hybrid and the Dodge Durango HEMI Hybrid. With the introduction of these vehicles, Chrysler will have two hybrid-electric vehicles that combine fuel-efficient advanced-hybrid technology with full-size sport utility vehicle (SUV) performance and capability.

“The new 2009 Chrysler Aspen and Dodge Durango HEMI Hybrid vehicles will offer our customers the sought-after blend of performance, utility, capability and vastly improved fuel economy—all in one package,” said Frank Klegon, Executive Vice President-Product Development, Chrysler LLC. “Combined with Chrysler’s Multi-displacement System (MDS), our advanced, two-mode hybrid technology immediately delivers a more than 25 percent fuel economy improvement to our full-size SUVs and up to a 40-percent improvement in the city.”

Capable of towing 6,000 pounds, the Chrysler Aspen and Dodge Durango HEMI Hybrid vehicles will deliver 385 horsepower—seamless, dependable power and performance on demand, in an efficient package. Equipped with an electrically variable transmission (featuring the best characteristics of an automatic transmission and hybrid drive) and two different modes of operation, the drive system will dramatically improve fuel economy around town and at highway speeds.

Chrysler’s advanced, state-of-the-art two-mode full hybrid system—developed in partnership with General Motors, Mercedes-Benz and The BMW Group—integrates proven automatic transmission technology with a patented hybrid-electric drive system to deliver the world’s first two-mode full hybrid.

As a result of low- and high-speed electric continuously variable transmission (CVT) modes, the system is defined as a two mode hybrid. Let’s take a closer look at these two modes, which are optimized for city and highway driving.

In the first mode—at low speed and with light loads—the vehicle can operate in three ways: (1) electric power only, (2) engine power only and (3) any combination of engine and electric power. The two-mode hybrid provides all of the fuel saving benefits of a full-hybrid system, including electric-only operation. In this mode, the engine is shut off, with the vehicle moving under electric-only power at low speed. The result is a significant reduction in fuel consumption in heavy stop-and-go city traffic.

The second mode is used primarily at highway speeds, in which the HEMI V8 is used, along with Chrysler’s Multi-Displacement System (MDS). In addition to electric assist, the second mode provides full power from the 5.7L HEMI V8 when conditions demand it (passing, pulling a trailer, climbing a steep grade). This system allows the HEMI V8 to remain in four-cylinder mode more often than it would without the hybrid powertrain.

A sophisticated controller determines when the vehicle should operate in first mode or second mode. Input from the controller determines the necessary torque for the driving conditions and sends a corresponding command to the electric motors and engine. Unlike conventional CVTs, the two-mode Chrysler system uses no mechanical belts or bands. Shifts between the two modes are synchronous (no engine speed changes are necessary for the mode shift to occur) resulting in seamless accelerations.

Finally, a 300-volt battery pack provides electric power for the system and is designed to fit in the vehicle without compromising passenger space. A rectifier converts AC to DC to power the conventional 12-volt accessories, such as the interior lighting, climate control system and the audio system. The vehicle’s HEMI V8 engine efficiently maintains the battery pack.