The minimum needed for 60mph cruising is about 20hp @ 2000rpm.


So given a 2-cylinder mode, you'd need a (20hp * 0.7 5th gear ratio / 2 cylinder mode * 6000 redline/2000rpm-cruise * 4cylinders) = 160hp/4-cylinder engine minimum. Probably 2.0 liter like you suggested. The problem with using a larger 2.0 liter instead of 1.3, is you have more mass, and therefore more energy losses from pistons constantly changing direction. Also a slightly-heavier car.

You'd be lucky to get 40mpg.




It is actually *more* efficient to just build a standard 4-cylinder 80hp engine, that has less mass, and therefore conserves energy... with estimated mpg=50.

troy