Valve timing optimisation of a spark ignition engine with skip cycle strategy

B. Dogru, R. Lot, K. K.J. Ranga Dinesh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Skip cycle strategy (SCS) is a stroke volume modulation method leading to reduction in pumping loss through deactivation of engine valves under part-load conditions. Although SCS achieves a significant fuel economy, it increases regulated pollutant emissions such as nitrogen oxide and unburned hydrocarbon in comparison to normal 4-cycle engine operation. This paper investigated normal cycle strategy, skip cycle strategy as well as combination of skip cycle strategy and variable valve timing strategy for a spark-ignition engine using one-dimensional numerical model. The skip cycle engine was modelled at several steady-state operation points and then optimised at best ignition timing providing maximum brake torque at each simulation case. The numerical results obtained for both normal cycle and skip cycle have been validated against the experimental data. After completing the validation of numerical results with engine test bench data for both normal and skip cycle operations, optimisation of intake and exhaust valve timing profiles have been carried out regarding advancing or retarding camshaft relatively to the crankshaft position. In case of SCS and variable valve timing application together, NOx concentration was reduced by 35.1%, 39.4%, 26.8% and HC emission was reduced by 54.9%, 49.3% and 47.4% on average for brake mean effective pressure load levels of 1, 2 and 3 bar respectively at all among engine speed ranges between 1200 and 1800 rpm compared to stand alone SCS strategy. Furthermore, no remarkable additional brake specific fuel consumption was observed for SCS plus variable valve timing strategy compared to stand alone SCS.

Original languageEnglish
Pages (from-to)95-112
Number of pages18
JournalEnergy Conversion and Management
Publication statusPublished - 1 Oct 2018
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018


The first author wishes to thank TUBITAK ( Scientific and Technological Research Council of Turkey ) 2219 Postdoctoral Research Scholarship Programme for financial support. The authors acknowledge Assistant Professor Doctor Osman Akin Kutlar from Istanbul Technical University for providing experimental data for numerical validation and optimisation.

FundersFunder number
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu


    • Fuel economy
    • Nitrogen oxide
    • Skip cycle
    • Unburned hydrocarbon
    • Variable valve timing


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