What is the efficiency of a gasoline engine?
2 Answers
Gasoline engine efficiency refers to the ratio of the thermal equivalent of the engine's effective power to the heat content of the fuel consumed per unit time, which is used to evaluate the economy of the engine as a heat engine. Range of gasoline engine efficiency: The efficiency of a gasoline engine ranges between 80% and 90%. From the perspective of energy conversion, the efficiency of converting electrical energy into kinetic energy is the highest, reaching up to 100%, and is generated by non-quasi-static processes (friction losses). Currently, the efficiency of a gasoline engine is generally one-fourth to one-fifth that of an electric motor, i.e., 20%. If the mechanical efficiency is taken as 0.85, the effective thermal efficiency of a gasoline engine is approximately between 20% and 35%; the effective thermal efficiency of a diesel engine ranges between 35% and 43%. Factors affecting gasoline engine efficiency: Leakage in the diesel engine combustion chamber and cylinder sealing, etc. Changes in the combustion chamber volume, such as replacing with a thicker cylinder gasket, intake efficiency (air filter clogging, turbocharger sticking, poor exhaust, camshaft wear, valve timing disorder, intake pipe leakage, poor diesel engine cooling heating intake, etc.), fuel injection and mixing efficiency. Carbon buildup causing injector seizure, fuel pump plunger wear, injector pressure drop, incorrect injection timing, etc.
I've been studying engines for a long time. The efficiency of a gasoline engine refers to how much of the power generated by burning gasoline is actually used on the wheels. On average, traditional gasoline engines have a thermal efficiency between 20% and 30%, meaning most of the energy is wasted as heat or mechanical friction. For example, older cars might be just over 20%, while newer engines with turbocharging can approach 35%, thanks to improvements in compression ratio and combustion efficiency. However, the key variables affecting efficiency are load and RPM—efficiency is higher during high-speed cruising and much lower during slow city driving. Engineers push the limits, like Mazda's Skyactiv-X compression ignition technology, which can reach up to 40%, but in reality, it also depends on maintenance—carbon buildup in the engine or incorrect air-fuel ratios can reduce efficiency. Understanding this not only optimizes performance but also greatly helps with fuel savings and cost reduction. I recommend paying attention to RPM matching while driving to minimize losses.
