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Gasoline Direct Injection
As the name implies, fuel in a gasoline direct injection (GDI) engine is injected directly into the combustion
chamber. The main advantage of this technology is that it enables lean operation of the engine, reducing fuel
consumption by up to 15% compared to a conventional engine.
Advanced Diesel Engines
Modern diesel vehicles equipped with advanced engines incorporating turbocharging, direct injection and common
rail or unit injector technology offer improvements in fuel efficiency of up to 40% over their gasoline
counterparts. Additionally, road performance and driveability of diesel vehicles now parallels or surpasses
that of gasoline vehicles making them attractive alternatives for the consumer.
Sequential Spark Ignition
Sequential spark ignition engines offer yet another option for controlling the combustion process. With this
technology, each cylinder incorporates 2 ignition plugs in a diagonal layout; one near the intake valve, and
the other near the exhaust valve. The spark plugs ignite the high swirl gas/air mixture at different places,
optimizing the combustion. The ignition timing between these plugs also varies depending on the driving
conditions. Due to this rapid, high pressure, and more complete combustion, an increase in torque can be
realized as well as a decrease in hydrocarbon emissions. A 10% to 15% increase in fuel efficiency is possible
with this technology.
Variable Valve Timing and Lift
This technology utilizes advanced electronic, hydraulic, pneumatic and mechanical means to vary the intake and
exhaust valve timing and lift of an engine. This enables the volumetric efficiency of the engine to be optimized
while meeting the torque and horsepower demands of the driver. This can often be accomplished with a smaller
engine. Most recent developments of this technology have permitted the elimination of the traditional intake
throttle on gasoline engines. Fuel consumption improvements of 6% to 8% are possible.
Cylinder Deactivation
Although not a new idea, the advent of more advanced computers and engine management systems and controls has
made cylinder deactivation a more attractive option for both diesel and gasoline engines. The deactivation is
accomplished by closing the intake and exhaust valves of the target cylinders using electronically controlled
hydraulic, pneumatic or electric actuators.
This means that an eight-cylinder engine could be operated on six or four cylinders at times of light power
demand. The transition from 8 to 6 or 4 cylinders and back would be seamless to the driver. Fuel consumption
could be reduced by 7% to 10%.
Variable Displacement
Variable displacement differs a little from cylinder deactivation. This process involves changing the swept
volume of the engine without changing the number of operational cylinders. This can be achieved by modifying
the stroke of each cylinder through the use of a pivoted lever arm attached at the crankshaft. This produces
an elliptical path for the connecting rod big end and modifies the stroke compared to a conventional engine.
Manufacturers of these engines have claimed a 40% cut in fuel consumption; however, no commercial models are
yet available for passenger vehicle applications.
Variable Compression Ratios
Variable compression ratio engines are able to modify the compression ratio, as a function of the vehicle
performance needs. The variable compression ratio engines are optimized for the full range of driving
conditions, such as acceleration, speed, and load. At low power levels, these engines operate at high
compression to deliver fuel efficiency benefits, while at high power levels; the compression ratio is
lowered to prevent knocking. Near-future engines are being designed with compression ratios ranging from
9.6:1 to 21:1. Improvements in fuel consumption of up to 30% are claimed.
Idle Stop
Idle Stop technology shuts off the engine during periods of idle when it is not necessary to have the engine
running and restarts the engine when there is a power demand. This feature is particularly useful in city
traffic where lots of stop-and-go driving is typical. The idle stop feature can reduce overall fuel consumption
by 6% to 8%. This technology is most effective with large capacity starter/generators as found on today’s hybrid
vehicles but also works with conventional starter motors.
Advanced Transmissions
The most common transmission types in Canada for light vehicles are the four-speed automatic and the five-speed
manual transmission. For the 2002 model year, about 67% of passenger cars were equipped with 4-speed automatics
and 25% with 5-speed manuals. For light trucks the statistics were 80% with 4-speed automatics and 6% with
5-speed manuals.
Adding more gears to either of these transmission types improves fuel consumption performance. Adding an infinite
number of gears, as is done with a continuously variable transmission (CVT), is another approach.
CVTs can reduce vehicle emissions and fuel consumption by better matching vehicle operational demands with engine
output. In many cases, engines can be downsized without degrading vehicle performance.
A new twist on the traditional manual transmission has been to take clutch operation duties away from the driver
and turn them over to the vehicle on-board computers and electro-hydraulic systems. The driver then has the option
of manually selecting gears or choosing an “automatic mode” and letting the vehicle handle all of the shifting
chores. Called electrically shifted manual transmissions, or ESMATs, these transmissions give the convenience of
an automatic transmission and the fuel efficiency of a manual.
These advanced transmissions can add significantly to better fuel efficiency. Compared to 4-speed automatic
transmissions, the alternatives can add the following improvements in fuel consumption:
- 4-speed automatic
baseline
- 5-speed automatic
2% to 3%
- 5-speed manual
5% to 7%
- 5-speed manual with ESMAT 6% to 8%
- 6-speed manual
6% to 8%
- CVT
4% to 5%
Supercharging and Turbocharging
The output of an internal combustion engine is proportional to the amount of fuel it can burn. To completely burn
fuel, the engine requires 14.7 parts air to 1 part fuel. Since fuel can easily be pressurized and forced into the
combustion chamber, an engine’s output is extremely dependent on its ability to flow large quantities of air in a
short amount of time. In conventional engines, the piston's movement to the bottom of the cylinder creates a
vacuum, drawing in air.
Superchargers and turbochargers are forced induction systems that incorporate compressors to force more air into
an engine. More air means that more fuel can be burned producing more power. Superchargers are typically driven
off an engine's crankshaft and produce boost in direct relation to engine speed. Turbochargers are driven by
waste heat and pressure in the exhaust gas exiting the combustion chamber.
By using superchargers and turbochargers, engines can be downsized without loss of output. This can yield fuel
savings of 10%. Aggressive driving will significantly reduce the savings or eliminate them altogether.
42V Electrical Architecture
42-volt electrical systems will enable the introduction of various electrically operated accessories such as
integrated starter/generators, electric power steering, air conditioner compressors and water pumps.
This combination can yield a 7% reduction in fuel consumption and be applicable to virtually the entire
car and light truck fleet.
Low Rolling Resistance Tires
Most tire manufacturers are developing high-efficiency tires that minimize rolling resistance while maintaining
safety and performance. These tires can offer 20% less rolling resistance when compared to high performance
radial tires. In city driving conditions, this can represent a fuel saving of some 3%, and 5% for highway usage.
Regenerative Braking
One way to reduce the amount of energy it takes to drive a vehicle is to recapture, store and reuse the kinetic
energy usually dissipated as waste heat during vehicle braking. Most electric and hybrid electric vehicles on
the road today accomplish this by operating the electric motor as a generator. This provides braking torque to
the wheels and simultaneously recharges the batteries. The energy captured by regenerative braking can then be
used for propulsion or to power vehicle accessories. The use of regenerative braking systems can also save on
mechanical brake wear and maintenance. Regenerative braking can increase overall energy efficiency by as much
as 30%.
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