This article presents selected results of preliminary tests that were carried out on a four-stroke engine with spark ignition (SI), as well as a mechanical oscillator with pneumatic support - the so-called pneumatic energy accumulator (PAE). This solution is expected to provide a significant improvement in the efficiency of SI engines in a range of partial loads. Due to the self-regulatory properties of the combustion chamber, the engine equipped with this type of oscillator is called an Active Combustion Chambers engine or, in short, an ACC engine. The aim of this study was preliminary to evaluate the possibility of controlling the thermodynamic processes that occur at the end of a compression stroke and at the beginning of an expansion stroke. It also aimed to carry out a preliminary assessment of a simulation model of a PAE (US 872039-B2). This article includes a diagram of an ACC engine with a brief description of the physical model of the oscillator. It also includes the mathematical description that was used for the simulation. As part of the analysis that was carried out, the article presents graphs of the simulation studies and empirical research.