Downsized, boosted gasoline engines
Aaron Isenstadt and John German
This technical brief highlights important innovations and trends in downsized and turbocharged gasoline engines, several of which were not considered when the 2025 CAFE standards were finalized, but promise to be quite cost-effective.
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Of all the engine improvements considered when the 2025 corporate average fuel economy (CAFE) and greenhouse gas standards were finalized by the Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA), the combination of turbocharging and downsizing was projected to occupy by far the biggest share of the market. Although turbocharger growth is slightly slower than predicted, it shows no signs of waning.
In fact, several unanticipated developments—Miller cycle, e-boosting with 48V mild hybridization, and variable compression ratio—will surpass the agencies’ efficiency projections. Coupled with well known, yet continuously improving, technologies like cooled exhaust gas recirculation and variable geometry turbochargers, downsized, boosted gasoline engines could realize efficiency improvements of 30% at a fraction of the cost of full hybridization.
Due to the wide variety of technologies enabling turbocharged and downsized engines, as well as additional consumer benefits, manufacturers have good incentives for offering these vehicles in their lineups.
View the full series of working papers and technical briefs on passenger vehicle technology trends in the U.S. here.