Sir Harry Ricardo, 90 years ago had engines with 4:1 compression ration, carburettors, and running on kerosene devlop better than 0.45 lb/hphr BSFC.
Not much these days will better that.
Power density is a different matter, as his 200hp engine was 6 cylinders, 186 c.i. per cylinder.
Look at the 1948 holden. Seatd 5 people. Did the speed limit comfortably, and got 30 plus miles per imperial gallon.
Modern Commondores seat 5 people, travel at the speed limit comfortably (well they can do twice the limt, but that's not possible). They get around 30 miles per imperial gallon.
Not much progress unless you count bells and whistles.
Not much these days will better that.
Power density is a different matter, as his 200hp engine was 6 cylinders, 186 c.i. per cylinder.
Look at the 1948 holden. Seatd 5 people. Did the speed limit comfortably, and got 30 plus miles per imperial gallon.
Modern Commondores seat 5 people, travel at the speed limit comfortably (well they can do twice the limt, but that's not possible). They get around 30 miles per imperial gallon.
Not much progress unless you count bells and whistles.