How the Ford Escape Hybrid Works
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
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
That's the point, really. The reason Ford took so much time
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.
How the Ford Escape Hybrid Works .
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:
1- 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
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
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.
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
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
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.
Escape Hybrid cockpit
PHOTO COURTESY FORD MOTOR COMPANY
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 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
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.