Comparison of hydrocarbon reduction in a si engine between continuous and synchronized secondary air injections

H. S. Sim, S. H. Chung*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Effect of secondary air injection (SAI) on hydrocarbon reduction has been investigated in a single cylinder SI engine operating at cold-steady/cold-start conditions. The hydrocarbon emission and exhaust gas temperature with and without catalytic converter were compared with continuous and synchronized SAIs, which injected secondary air intermittently into exhaust port. Effects of SAI location, SAI pressure, SAl timing, and location of catalytic converter have been investigated and the results are compared for both SAIs with base condition. At cold-steady condition, the rate of HC reduction increased as the location of SAI was closer to the exhaust valve for both synchronized and continuous SAIs. The emission of HC decreased with increasing exhaust-A/F when it was rich, and was relatively insensitive when it was lean. The timing of SAI in synchronized SAI had significant effect on HC reduction and exhaust gas temperature and the synchronized SAI was found to be more effective in HC reduction and exhaust gas temperature compared to the continuous SAI. At cold-start condition, when the catalytic converter was located 20 cm downstream from the exhaust port exit, the catalytic converter warm-up period for both SAIs decreased by about 50%, and the accumulated hydrocarbon emission during the first 120 s decreased about by 56% and 22% with the synchronized and continuous SAIs, respectively, compared to that of the base condition.

Original languageEnglish (US)
Pages (from-to)41-46
Number of pages6
JournalInternational Journal of Automotive Technology
Issue number1
StatePublished - 2002
Externally publishedYes


  • Continuous SAI
  • Hydrocarbon
  • SI engine
  • Secondary air injection (SAI)
  • Synchronized SAI

ASJC Scopus subject areas

  • Automotive Engineering


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