The Journal of Engine Research

The Journal of Engine Research

Comparison of the Otto cycle and the Atkinson cycle with an optimized intake cam profile for a turbocharged spark-ignition engine

Document Type : Original Article

Authors
1 Faculty of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
2 Irankhodro Powertrain Company (IPCo), Tehran, Iran
10.22034/er.2026.2078266.1120
Abstract
This study investigates the performance of a spark-ignition engine featuring an increased effective compression ratio, achieved by implementing the Atkinson cycle through intake cam profile design. A conventional four-stroke, turbocharged spark-ignition engine with a geometric compression ratio of 9.2 and a peak power output of 112 kW served as the baseline. A validated 1D engine simulation model was developed, incorporating in-cylinder pressure calibration based on a turbulent combustion model. Using this model, Atkinson-cycle operation was realized via intake camshaft optimization. Engine performance was evaluated across a wide range of speeds and loads, focusing primarily on brake-specific fuel consumption (BSFC), torque, and overall fuel economy. A comparative analysis was conducted between the baseline engine and the optimized Atkinson-cycle configuration. The results indicate that optimizing the intake valve timing yields an approximate 2–3% reduction in average fuel consumption, achieving a 2.5% overall improvement. These findings demonstrate that implementing the Atkinson cycle via valve timing modifications effectively enhances fuel economy under the investigated operating conditions.
Keywords

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Volume 72, Issue 4 - Serial Number 81
English Paper
Winter 2026
Pages 50-63

  • Receive Date 04 January 2026
  • Revise Date 28 February 2026
  • Accept Date 01 May 2026