Car Combustion and Emission Control

The Combustion and Emission Control research and development (R&D) focuses on enabling technologies for energy-efficient, clean vehicles powered by advanced internal combustion engines using clean, hydrocarbon and non-petroleum-based fuels, and hydrogen. Work focuses on developing technologies for light-, medium-, and heavy-duty compression-ignition direct-injection (CIDI) engines and is being transitioned to developing technologies for engines operating in advanced combustion regimes that will further increase efficiency and reduce engine-out emissions of nitrogen oxides (NOx) and particulate matter (PM) to near-zero levels.

Research Goals

  • By 2007, achieve CIDI efficiency of at least 41% and combined with emission control devices, meet EPA Tier 2, Bin 5 emission standards in a light-duty vehicle using diesel fuel (specified by the Fuels Technologies activity) with a fuel efficiency penalty of not more than 3%.
  • By 2012, develop the understanding of novel low-temperature engine combustion regimes needed to simultaneously enable engine efficiency of 45% with a fuel efficiency penalty of less than 1%.

Advanced internal combustion engines are the most promising technology for achieving dramatic energy-efficiency improvements in light-duty vehicles. They are suited to both conventional and hybrid electric powertrain configurations. Although these engines are more efficient than conventional gasoline engines, technology advances will be required in the mid-term to further improve efficiency and offset the efficiency penalties of meeting more stringent future emissions standards.

Efficiencies higher than that of current diesel engines combined with dramatically lower emissions can be achieved by engines operating in advanced combustion regimes. Because they can potentially be less expensive, these engines can overcome key technical barriers: emissions and cost. Advanced combustion engine technologies being investigated include those operating purely in low-temperature combustion (LTC) modes, such as the homogeneous charge compression-ignition (HCCI), to engines that operate in “mixed modes” that utilize conventional combustion modes for starting and at higher loads, and LTC modes at light to moderate loads.


The approach of this research activity is to simultaneously address in-cylinder combustion and emission control, exhaust aftertreatment technologies, and fuel formulation strategies for the most cost-effective approach to optimizing advanced combustion engine efficiency and performance while reducing emissions to meet future U.S. Environmental Protection Agency (EPA) standards. Results are applicable to engines of both passenger vehicles (cars and light trucks) and commercial vehicles (medium and heavy trucks and buses).

In the longer term, further improvement of advanced engine designs being considered (such as increased expansion ratio, improved exhaust heat recovery, variable valve timing, reduced friction) and minimization of the emission reduction fuel economy penalty offer the potential for further gains in fuel efficiency for heavy- and light-duty vehicles.


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