Direct Injection Propane for Advanced Combustion

Bradley Zigler

Research output: NRELManagement


For on-road transportation, propane, also known as liquefied petroleum gas (LPG) or propane autogas, is primarily used in spark-ignition (SI) engines adapted from existing original equipment manufacturer (OEM) gasoline engines in cars, light-duty trucks, and medium-duty trucks. Similar to natural gas, dual-fuel adaptations of propane fumigated in the intake air stream of a compression-ignition (CI) heavy-duty (HD) truck engine have also been attempted but are not currently common in the United States. In light- and medium-duty SI engines, propane is commonly used in a bi-fuel strategy in which gasoline is used for the cold start with OEM controls, switching over to propane through additional port fuel injection (PFI) injectors added to the intake manifold, controlled by a piggy-back slave engine control unit using OEM gasoline injector signal inputs after the engine is warmed up. Monofuel propane SI engines have also been available but are less common.
Original languageAmerican English
Number of pages6
StatePublished - 2020

Bibliographical note

See the Vehicle Technologies Office Advanced Engine and Fuel Technologies 2019 Annual Progress Report at

NREL Publication Number

  • NREL/MP-5400-78754


  • engine efficiency
  • liquefied petroleum gas (LPG)
  • propane
  • propane blends


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