Date of Award


Publication Type


Degree Name



Mechanical, Automotive, and Materials Engineering

First Advisor


Second Advisor


Third Advisor



Combustion, Plasma electrolytic oxidation, Coating, Piston surface, Spark ignition engine



Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


With the global effort to “green” the transportation industry, the internal combustion engine (ICE) is required to reduce its carbon footprint and can do so by increasing efficiency. Plasma Electrolytic Oxidation (PEO) coatings confer properties of high wear and corrosion resistance, high hardness, excellent adhesion and a superior thermal barrier to their substrate, suggesting that coating of ICE components has the potential to greatly improve the combustion efficiency. The primary objective of this thesis is to analyze the effects of PEO coating on the surface of pistons in a spark ignition ICE, with the goal of increasing efficiency, to address the industry targets of reduced carbon emissions and increase fuel efficiency.

Testing was conducted on a 7.3L Ford engine fitted with stock Al alloy pistons, followed by in-house PEO-coated pistons. An AC Medien dynamometer and a A&D Pheonix AM/RT combustion analysis system using real-time in-cylinder pressure data, coupled with the dynamometer cell data were used. The testing was built off real world driving cycles overlaid on a brake specific fuel consumption (bsfc) map, to choose areas upon which to focus during the completion of the spark and VCT timing sweeps at both, low load and high load conditions.

Compared to stock pistons, the PEO-coated pistons modestly improved bsfc, thermal efficiency, increased HRR and bulk gas temperature at low load, low speed conditions. These benefits did not project further onto retarded VCT angles and higher speeds, where PEO-coated pistons did not change thermal efficiency, bfsc, had minimal impact on bulk gas temperatures, and minimally influenced the IMEP COV. At high load and speed conditions the PEO-coating negatively impacted the engine performance, inducing knock. An increased fuel enrichment was required to reduce exhaust temperature limits, since retarding spark was required to reduce knocking. The engine could not be run at optimum efficiency or MBT spark timing, decreasing the bsfc and thermal efficiency.

In conclusion, although benefit derived from the use of PEO-coated pistons was observed only in limited engine conditions, the data collected and analyzed in this thesis provides a direction for future study to continue to explore the potential advantages of PEO-coated pistons.