Skip cycle system for spark ignition engines: An experimental investigation of a new type working strategy

Osman Akin Kutlar*, Hikmet Arslan, Alper T. Calik

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


A new type working strategy for spark ignition engine, named skip cycle, is examined. The main idea is to reduce the effective stroke volume of an engine by cutting off fuel injection and spark ignition in some of the classical four stroke cycles. When the cycle is skipped, additionally, a rotary valve is used in the intake to reduce pumping losses in part load conditions. The effect of this strategy is similar to that of variable displacement engines. Alternative power stroke fractions in one cycle and applicability in single cylinder engines are specific advantageous properties of the proposed system. A thermodynamic model, besides experimental results, is used to explain the skip cycle strategy in more detail. This theoretical investigation shows considerable potential to increase the efficiency at part load conditions. Experimental results obtained with this novel strategy show that the throttle valve of the engine opens wider and the minimum spark advance for maximum brake torque decreases in comparison to those of the classical operation system. The brake specific fuel consumption decreases at very low speed and load, while it increases at higher speed and load due to the increased fuel loss within the skipped cycles. In this working mode, the engine operates at lower idle speed without any stability problem; and moreover with less fuel consumption.

Original languageEnglish
Pages (from-to)370-379
Number of pages10
JournalEnergy Conversion and Management
Issue number2
Publication statusPublished - Feb 2007


This research was supported in part by the State Planning Organization of Turkey, Institute of Science and Technology of Istanbul Technical University, Anadolu-Motor Co., Taral Co. and Tofas-Fiat Co.

FundersFunder number
Anadolu-Motor Co.
Tofas-Fiat Co.
Devlet Planlama Örgütü
Istanbul Teknik Üniversitesi


    • Fuel consumption
    • Part load
    • Power frequency
    • Pumping loss
    • Skip cycle system (SCS)
    • Spark ignition (SI) engine


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