The significance of octane numbers to drive cycle fuel efficiency

Modern spark-ignition engines are knock-limited over a significant fraction of their operating map. The efficiency loss induced by knock mitigation depends on both the fuel octane quality and driving conditions. This paper quantifies relevance Research Octane Number (RON) Motor (MON) to losses (KLFEL) mid-size sports utility vehicle operated in several standard drive cycles. Index model, OI = (1-K)·RON + K·MON, is used with K as weighting factor evaluate relative importance RON MON. K-map recently obtained for gasoline turbocharged direction-injection engine (Zhou et al., Fuel 290 (2021) 120012) determine distribution these analysis shows that not significantly limited city highway However, becomes major constraint under more aggressive conditions such US06 cycle hot-weather towing tests, where approximately 70% consumption occurs KLFEL accounts up 6.3% total consumption. Among cycles studied, KLFEL-weighted ranges from ?0.44 +0.12, indicating increasing would improve decreasing MON have only minor effect.