Power denity
How about we build an engin that has 1.5 times the power, even at 75% max power density you get 1.1 times the output and have fule usage of 75% of the original engin. As well you have more power and torque in the normal range.
Best idea is still to combine this engin with an electric drivetrain, new batteries, and also lets put some reseach into improving energy production as well as energy storeage.
Imagin a plug in electrice, with a high efficency gas/diesel engin powering a next gen alternator.