And not the kind of efficient that makes the EPA happy.
Shortly after the Mercedes-AMG Project One made a splash in the hypercar world, a report came out detailing how Mercedes' Formula 1 engines had cracked the magical barrier of 50% thermal efficiency for their engine. Competitors ranted, fans raved, but few knew exactly what that breakthrough meant, much less what it implied for the future of the internal combustion engine. If you find yourself in the latter camp, have no fear because that's what this episode of Engineering Explained is for.
Before Jason Fenske gets into his explanation, let us talk about the logical aspects of engine thermal efficiency. An engine takes in fuel and air and using heat, compression, and a spark, ignites the mixture. The byproducts of that are violent kinetic energy, exhaust, and heat.
Throughout the entire history of the engine, that energy locked inside the fuel that was converted to heat was considered a loss. There's not really a way to capture thermal energy and turn it into any sort of energy the car can use unless you count warming up the cabin in winter. However, the amount of energy that's sequestered through the other two combustion byproducts can be increased, and that's just what Mercedes has done. Mercedes manages this by extracting more kinetic energy out of the combustion process and by using exhaust gases to add power to the engine using a turbocharger. While these techniques aren't feasible for passenger cars today, that may not remain the case for long.