Variable
Valve Timing & Lift (VVT&L)
Also called variable valve actuation (VVT),
variable-cam timing and variable
valve timing and lift electronic control (VTEC®)
Valves
control the flow of air and fuel, into the cylinders and exhaust
out of them. When and how long the valves open (timing) and how
much the valves move (lift) both affect engine efficiency.
Optimum timing and lift settings are different for high and low
engine speeds. Traditional designs, however, use fixed timing and
lift settings, which are a compromise between the optimum for high
and low speeds. VVT&L systems automatically alter timing and
lift to the optimum settings for the engine speed.
Potential Efficiency
Improvement: |
5% |
Savings Over Vehicle Lifetime: |
$1,100* |
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Cylinder Deactivation
Also called multiple displacement, displacement
on demand (DOD), and variable cylinder
management
This
technology merely deactives some of the engine's cylinders when
they are not needed. This temporarily turns a 8- or 6-cylinder engine
into a 4- or 3-cylinder engine. This technology is not used on 4-cylinder
engines since it would cause a noticeable decrease in engine smoothness.
Potential Efficiency
Improvement: |
7.5% |
Savings Over Vehicle Lifetime: |
$1,600* |
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Turbocharging
& Supercharging
Turbochargers
and superchargers are fans that force compressed air into an engine’s
cylinders. A turbocharger fan is powered by exhaust from the engine,
while a supercharger fan is powered by the engine itself.
Both technologies allow more compressed air and fuel
to be injected into the cylinders, generating extra power from each
explosion. A turbocharged or supercharged engine produces more power
than the same engine without the charging, allowing manufacturers
to user smaller engines without sacrificing performance.
Potential Efficiency
Improvement: |
7.5% |
Savings Over Vehicle Lifetime: |
$1,600* |
Additional Information:
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Direct Fuel Injection
(with Turbocharging/Supercharging)
Also called fuel stratified injection
or direct injection stratified charge
In
conventional multi-port fuel injection systems, fuel is injected
into the port and mixed with air before the air-fuel mixture is
pumped into the cylinder. In direct injection systems, fuel is injected
directly into the cylinder so that the timing and shape of the fuel
mist can be precisely controlled. This allows higher compression
ratios and more efficient fuel intake, which deliver higher performance
with lower fuel consumption.
Potential Efficiency
Improvement: |
12% |
Savings Over Vehicle Lifetime: |
$2,600* |
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Integrated Starter/Generator
(ISG)
These systems automatically turn the engine off when the vehicle
comes to a stop and restart it instantaneously when the accelerator
is pressed so that fuel isn't wasted for idling. In addition, regenerative
braking is often used to convert mechanical energy lost in braking
into electricity, which is stored in a battery and used to power
the automatic starter.
Potential Efficiency
Improvement: |
8% |
Savings Over Vehicle Lifetime: |
$1,700* |
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* Fuel cost savings are estimated assuming an average vehicle lifetime
of 185,000 miles, a fuel price of $2.44, and an average fuel economy
of 21 MPG. All estimates are rounded to the nearest hundred dollars.
**Some documents on this page are provided as Adobe Portable Document
Format (PDF) files. Any PDF file can be downloaded, viewed on screen,
and printed using the Adobe
Acrobat Reader software. This free software can be downloaded
from the Adobe Web site. Installation and setup instructions are
provided on this site.
Data Sources
Potential fuel efficiency improvement: Energy and Environmental
Analysis, Inc. 2005. Automotive Technology Cost and Benefit
Estimates. Arlington, Virginia, March.
Average light-duty vehicle fuel economy: Heavenrich, R. M.
2005. Light-Duty Automotive Technology and Fuel Economy
Trends: 1975 Through 2005. Office of Transportation and
Air Quality, U.S. Environmental Protection Agency, Washington,
D.C.
Average vehicle lifetime: Calculated based on Transportation
Energy Data Book, Edition 24. Oak Ridge National Laboratory,
Oak Ridge, Tennesse, Tables 3.9 & 8.13. |
|