Feel the burn

Combustion technology has undergone a quiet revolution in the last decade. We look at the strategies employed to maximise thermal efficiency

- JAHEE CAMPBELL-BRENNAN

Thermal efficiency is a term that has been thrown around engineering circles for decades. While not necessarily immediately obvious in definition, it is one of the primary measures of internal combustion engine performance.

Last month, Racecar Engineering explored the journey of efficiency, specifically within Formula 1 development, over the last years. Building on that, in this article we will explore the technical advancements in depth with the aim of understanding how they have advanced the combustion process to extract maximum energy from fuel.

Being a hydrocarbon, petrol contains chemical energy that, upon oxidisation (combustion) is released as heat energy. The energy contained within the atomic bonds of a fuel is measured by the amount of heat released in its combustion, in joules (J), which establishes the link between the amount of fuel burned and the heat, or thermal input.

In the context of engine performance, measuring thermal efficiency allows us to satisfy questions such as how much fuel is needed to generate a particular amount of engine power?

Considering a more technical definition, we understand it as the engine output (kW) measured at the flywheel, divided by the fuel energy (kW) supplied to the engine. The two have an inversely proportional relationship so, if the fuel required for a given power output decreases, thermal efficiency increases.

Road car engines have been focussing intensely on maximising thermal efficiency for decades now, as lower fuel consumption is a clear selling point for any potential consumer. Motorsport, on the other hand, hasn’t traditionally shared the same concerns. Historically, power has been generated without much emphasis on efficiency, but nowadays the two sectors are steaming ahead on the same mission, just with very different driving forces.