The present paper summarizes results of experimental trails with the SI and HCCI engine fuelling with a producer gas substitute. Both engines are single cylinder units with similar displacement volume. In its original version, the HCCI engine used to be a three cylinder CI engine. Two of those cylinders were disabled when the engine was modified for the HCCI operation. The SI engine used in this was a component of commercially available generator. The engine original intake manifold and ignition system were rebuild for the purpose of this study. Engines were fuelled with the producer gas substitute that simulated real producer gas composition. The SI engine was charged with a stoichiometric air/fuel mixture, while the HCCI engine with a lean air/fuel mixture with equivalence ratio of 0.5. The main control variable in the SI engine operation was the spark timing. The initial air preheat temperature was the equivalent control variable in the HCCI engine trials. This paper reports on both engines indicated performance and combustion phasing parameters that were derived based on in-cylinder, cycle resolved pressure measurements. (C) 2016 Elsevier Ltd. All rights reserved.