What is SULEV?
engineers determined that the
restrictive California air emission standards would be impossible
to attain using a traditional gasoline-fueled internal combustion
engine. Instead, they focused their efforts on alternative
fuels, such as hydrogen and compressed natural gas (CNG), or
emerging technologies, like fuel cells or gasoline-electric
To achieve the
SULEV rating, the BMW 3 Series SULEV must be fueled with specially
formulated low-sulfur gasoline; however, there is no loss of
performance if the vehicle is fueled with higher sulfur content
fuel, although SULEV emissions might not be attained.
The SULEV engine works to accomplish four main goals:
engine-out hydrocarbons to restrict the number of
hydrocarbons released into the atmosphere upon ignition and
throughout the powerband.
catalyst light-off time to abbreviate the catalyst (exhaust)
period between detonations.
hydrocarbon trap efficiency through the use of multiple
advanced filters, to virtually eliminate hydrocarbon emissions.
Stabilize catalyst efficiency to improve the efficacy of
catalytic exhaust processing, thereby further reducing
government and California (along with New York, Massachusetts,
Vermont and Maine currently) have their own emissions rules, and
having two sets of standards invites confusion. Decades ago --
before there were any national automotive emissions standards --
California mandated its own, more restrictive emissions rules to
ameliorate the severe smog problems in California. Over
time, these rules have gradually become not only the standard for
the state, but also the standard for the nation and the world.
Though there are many different aspects of vehicle emissions that
need to be monitored and limited, the three most important factors
are considered to be carbon monoxide (CO), oxides of nitrogen (NOx),
hydrocarbons (HC), and the accompanying particulate matter. Among
these, NOx and particulate matter are most directly associated
with smog. Besides being linked to smog problems and changes in
the upper atmosphere, each of these pollutants is associated with
health risks, including respiratory problems and other long-term
Cars and light trucks that only comply with the US
Federal Government's 'Tier 1'
emissions are the
least-green new cars in terms of tailpipe emissions.
(transitional low-emission) standard is similar to the Tier 1
federal standard, but with tighter limits on hydrocarbons to aid
the state’s smog-prone valleys.
vehicles adhere to a tighter standard than most passenger cars now
meet. The LEV standard for oxides of nitrogen is half that of TLEV
and Tier 1, and the allowance of hydrocarbon emissions is further
tightened. Cars complying with LEV standards are now widely
(ultra-low-emission) vehicles further reduce the permissible
levels of hydrocarbons and carbon dioxide emissions by 50 percent,
compared to LEV. Many models now meet ULEV standards in
California, but not necessarily in other states. In simple terms,
cars rated ULEV are up to 50 percent cleaner than LEV cars.
(super-ultra-low-emission) is the new emissions standard to meet.
The SULEV standard—about 90 percent cleaner than LEV—is a big leap
forward. It requires emissions equipment to perform within the
standards for 150,000 miles, and dramatically reduces the allowed
amounts of hydrocarbon and carbon dioxide emissions. Only two
non-hybrid gasoline-engine vehicles met SULEV standards for 2002:
- Honda Accord (four-cylinder, automatic only)
- Nissan Sentra
CA (a special California model)
Federal 'Tier 2'
standards will be required nationwide beginning in 2004. Along
with California’s tighter new minimum requirement called LEV II,
they require all vehicles to comply with much tighter limits on
hydrocarbons and particulate matter—still not as tight as SULEV standards.