How the Ford Escape Hybrid Works

Hybrid vehicles offer the best fuel economy of any car on the market by combining an efficient gasoline engine with an electric motor and batteries that are constantly recharged. Until 2005, most hybrid cars were small, and they didn't have much horsepower or cargo space. The Ford Escape Hybrid changes all that.

The Escape Hybrid is an SUV that gets up to 36 miles per gallon. That may not be as ultra-efficient as some hybrids, but it definitely saves the average family of four a lot of money at the gas pump.

In this article, we'll learn about Ford's brand new, patented hybrid powertrain, take a look at the Escape Hybrid's performance and find out why this car could be a major breakthrough for hybrids in the automotive marketplace.

A hybrid car is one that attempts to incorporate the strengths of both gasoline-fueled combustion engines and electric motors while eliminating many of the problems that plague cars that are only one or the other. For gasoline cars, these problems include noise, expensive fuel and polluting emissions. Battery-powered electric cars have always been held back by short battery life and the need to plug the car in to recharge it.

A hybrid car has a combustion engine and an electric motor that work together (either at the same time or separately, depending on the type of hybrid). The image below shows a parallel hybrid car, in which both the gasoline engine and the motor can propel the vehicle.

A hybrid car never needs to be plugged in for a recharge -- whenever you step on the brakes, some of that energy is stored in the batteries. If the batteries get really low, the car can just run on gas until the combustion engine recharges them.

For a more detailed, in-depth explanation of hybrid cars, check out How Hybrid Cars Work.

Now, let's take a look at the Ford Escape Hybrid.

Ford didn't try to design an all-new car for their first foray into the hybrid realm. It started with a proven model, the four-cylinder Ford Escape, and spent five years and 100 engineers (Car and Driver, Dec. 2004) developing a hybrid powertrain to put into it. The Escape itself is recognizable as an SUV, but it is a relatively small one. In that respect, the Escape gets good mileage even without an electric motor: It's rated at 25 mpg on the highway.

So what did all those engineers do to convert the Escape? In terms of looks, not much. Except for the small "Hybrid" logo on the door, a different gauge in the dashboard and a vent in the rear to help cool the batteries, you'd be hard-pressed to tell an Escape Hybrid from the conventional version.

That's the point, really. The reason Ford took so much time developing the Escape Hybrid is that it wanted the car to function just like a regular SUV. The driver doesn't need any special technical skills to operate it. The electric motor and batteries are supposed to operate for the life of the vehicle without maintenance. There isn't even a meter to tell the driver how low the battery charge is getting, because the driver isn't supposed to worry about it. The operation of the hybrid system is as transparent as possible. For all intents and purposes, the Escape Hybrid is just an SUV that gets great mileage and doesn't give off much pollution. That's the reason it could make a significant impact on the U.S. auto market. Making hybrid technology easy for the average buyer to adopt is probably the most innovative aspect of the Escape Hybrid.

Now, let's take a closer look at the nuts and bolts (and wires and batteries) that lie beneath the Escape Hybrid's hood.

The Ford Escape's Full Hybrid System

All hybrid cars have two power sources -- a gasoline engine and an electric motor. They can work together in different ways, however. In so-called "mild" hybrid designs, the gasoline engine is always running, and the electric motor simply augments it, adding a little extra horsepower here and there to save some fuel. But Ford developed a full hybrid system for the Escape.

In a full hybrid system, the gasoline engine and the electric motor can both operate separately, or they can run at the same time. The Escape's hybrid system operates in four phases:

Start/Stop - When you turn the ignition key of the Escape Hybrid, the electric motor comes to life. The electric motor, in turn, starts the gasoline engine. The car then performs a series of checks to determine if it can switch to electric-only operation: It checks to see if the batteries are charged, if the operating temperatures are okay and if interior climate control settings are in the appropriate range (the air conditioning's maximum setting requires the gasoline engine to run). If everything checks out, the engine will then shut off, leaving the car running under electric-only power. This process only takes a second or two. When you come to a stop in the Escape Hybrid, the gasoline engine actually shuts off. The car runs on electric-only while you're at a stoplight or waiting in line at the drive-thru. Ford put a lot of effort into making the gasoline engine on-off cycles as smooth and seamless as possible, but testers reported a discernible shudder in the vehicle when the engine went on or off. This is common to all hybrid cars.
Electric Drive - As the Escape Hybrid accelerates from a stop, it does so under electric power. Electric motors are good at generating torque at lower rpm ranges, so they're perfect for this purpose. At about 25 mph, the gasoline engine starts back up. If you're driving in heavy city traffic, you could go all day using only electric power. The electric motor and gasoline engine operate in tandem up to highway cruising speeds.
Regenerative Braking - Whenever you apply the brakes on a car, the kinetic energy of the car's movement is dissipated as heat. In a hybrid car, the brakes take some of that energy and, using the electric motor as a generator, put power back into the batteries. This is why hybrids actually get better mileage in start/stop city driving than they do on open highways. Every red light recharges the batteries. To maximize the power of regenerative braking, it's important to stop smoothly and gradually. Slamming on the brakes activates the regular anti-lock braking system, and the energy is wasted.
Electric Assisted Cruising - At highway cruising speeds (roughly 50 to 70 mph or 80 to 110 kph), the gasoline engine does most of the work. It's most efficient at this speed range. But because the Escape Hybrid has a small, four-cylinder engine, it needs a little help when passing. When a speed boost is called for, the electric motor kicks in and adds its horsepower to that of the gasoline engine.

The Escape Hybrid (along with all other hybrid cars) doesn't have the usual transmission, with separate gears for the car to shift into and out of. Instead, the Escape uses an electronically controlled continuously variable transmission (eCVT). On-board computers set the gearing to the optimum setting for fuel efficiency, resulting in a 30 percent increase in efficiency over a conventional transmission, according to Ford engineers.

Next, we'll crunch some numbers and see how the Escape Hybrid measures up.

Ford Escape Hybrid Specs

To improve efficiency in the gasoline engine itself, Ford used a four-cylinder Atkinson-cycle engine in the hybrid version of the Escape. Atkinson engines are more fuel efficient than standard-cycle engines (known as Otto-cycle engines) at the expense of horsepower. To learn about the Atkinson cycle, see Lindsay Publications: Atkinson Cycle Engine.

The Escape Hybrid's 2.3-liter, aluminum, four-cylinder, dual overhead cam engine generates 133 horsepower at 6,000 rpm. The three-phase, permanent-magnet, synchronous electric motor adds 94 horsepower in the 3,000-5,000 rpm range. By itself, the gasoline engine can crank out 129 lb-ft of torque at 4,500 rpm. (For comparison, the four-cylinder engine in the non-hybrid Escape generates 153 hp at 5,800 rpm and 152 lb-ft of torque at 4,250 rpm.)

The AWD Escape Hybrid weighs in at 3,893 lbs (1,766 kg) -- the hybrid components add about 500 pounds (230 kg) to the Escape's weight. With a wheelbase of 103.1 inches (261.9 cm) and an 8-inch (20-cm) ground clearance, it's a relatively compact SUV. The Escape rides on Continental ContiTrac EcoPlus tires (spare included). The fuel tank holds 15 gallons.

According to Car and Driver magazine (Dec. 2004), the AWD Escape Hybrid with a full options package accelerates from zero to 60 mph (97 kph) in 10.8 seconds, has a top speed of 102 mph (164 kph) and goes from 70 mph (113 kph) to a full stop in 195 feet (60 meters).

For anyone interested in buying a hybrid, one of the most important numbers is the fuel mileage. The Escape won't come close to the 50 mpg or more offered by compact hybrids. Ford rates it at 35 mpg in town, 29 mpg on the highway. Several different tests (USAToday, 5/13/04; Motor Trend, Aug. 2004) showed the real numbers will probably be a few miles per gallon lower, but the Escape Hybrid still offers a 20 to 25 percent increase in fuel economy over the non-hybrid Escape and a huge gain over larger SUVs that barely manage 10 mpg.

The Ford Escape Hybrid comes in either front-wheel-drive (FWD) or all-wheel-drive (AWD) varieties. The official EPA mileage rating for the FWD version is 33 mpg in the city and 31 to 36 mpg on the highway. For the AWD version, it's 33 mpg in the city and 29 on the highway. With those numbers, one tank of gas should give you a range of 400 to 500 miles (650 to 800 km).

Check out the next section to find out what it's like to drive an Escape Hybrid.

Hybrid City/Highway Efficiency

A combustion engine is inefficient in taking a heavy car from a stop all the way up to speed -- it burns a lot of gas. And in a city, you do that every five blocks or so. So a car powered only by a gasoline engine gets better mileage on the highway, where there are fewer stops and starts. A hybrid car can operate on electric-only at low speeds, so it's not burning gas during stops and starts. Also, every stop recharges the battery. Hybrids therefore get better city mileage than on the highway, where the combustion engine does most of the work.

Driving a Ford Escape Hybrid

For the most part, driving an Escape Hybrid is like driving a non-hybrid Escape, or any other small SUV for that matter. Ford went to great lengths to ensure that you wouldn't even realize you were driving a hybrid if someone didn't tell you.

On the other hand, there are a few quirks that show up on the road, like the aforementioned shudder when the gasoline engine kicks in. The regenerative braking system also feels different, since the speed is being reduced in a different way from standard disc brakes -- you can feel it when the regular brakes kick in on a hard stop.

On the up side, another difference comes from the transmission. Along with the reported increase in fuel efficiency that comes from using an electronically controlled continuously variable transmission (eCVT), there is also a smoother ride. There's no sudden jolt when the car upshifts or downshifts.

The rear seats can be folded down to allow up to 65.5 cubic feet of cargo space.
Photo courtesy Ford Motor Company Photo courtesy Ford Motor Company

The only change to the dashboard is on the tachometer, which features a reading below zero that indicates when the engine has shut off and the car is on electric-only power. If the navigation system is purchased, then the display screen has a hybrid power flow graphic.

You might think that the batteries needed to power a small SUV would take up most of the cargo space. In fact, the Escape Hybrid's 250 D-size, nickel-metal hydride cells (connected in series) lie flat beneath the rear cargo area.

That cargo area is smaller than the cargo space in the non-hybrid Escape, but only by a few inches. The space for driver and passengers is unchanged.

As a first attempt to create a practical hybrid SUV, the Ford Escape Hybrid is an excellent piece of engineering. It's definitely better for the environment and offers lower fuel costs than any other SUV on the market. Although it isn't as environmentally friendly as a Toyota Prius, rated at 60 mpg in the city and 51 mpg on the highway, it may be better for the planet in the long-term. By making a hybrid for the average family, which generally needs a bit of room to travel comfortably, Ford could be helping to put millions of hybrids in American garages within a decade.

For more information on the Ford Escape Hybrid and related topics, check out the links on the following page.

Lots More Information

Sources

Chirico, Neil. "First Drive: 2005 Ford Escape Hybrid." Motor Trend, Aug. 2004.
Healey, James. "Ford goes hybrid with promising new Escape." USAToday.com, 5/13/2004.
Sessions, Ron (editor). "Motor Trend 2005 & 2006 Sport/Utility, Truck & Van Buyer's Guide." Motor Trend, Nov. 2004.
Vanderwerp, Dave. "After a million man-hours, Ford cranks out the first hybrid SUV." Can and Driver, Dec. 2004.
Ford Vehicles: Escape Hybrid