Because my head is the thickest part of me, I still haven't fully wrapped it around this piston speed thing. So I did a lil lookin' at some numbers:
Tempo seems to be geared spot-on for the 1000-1200 ft/mn piston speed theory, as that calc's out to 50-60 mph. It was made in the era of the national 55 mph speed limit, so that makes perfect sense.
Gold Wing 1100 has 1297 piston speed at 55 mph- winding out a little fast? It always did give me the impression of "wanting" a slightly taller gear. 1000-1200 ft/mn gives a calc'd 42-51 mph cruise speed. Makes sense too, I can see the bike getting way better fe at those speeds vs 55. It's got horrible aero and a very lossy drivetrain too.
I wonder how much it would benefit with a higher final drive unit that pulls the ft/mn to, say, 1100 at 55?
Honda Super Cub 50: Interestingly enough, the stats I found for max fe (343 mpg) said it was tested at 19 mph which calc's out to 1,168 ft/mn piston speed- nicely within the 1000-1200 parameters even for such a small one-lunger!
And this engine is capable of a 9500 rpm redline (?) which is 2580 ft/mn.
1994 F150: OK now I'm baffled. The above three seemingly agree with the piston speed theory. But this truck has a calc'd engine rpm of 1500 @55 mph; with the 3.0" stroke that's 825 ft/mn piston speed- way too slow according to theory. Calc'd speed for my F150 at 1000-1200 ft/mn is 73-88 mph!
I know for a fact the fe on that truck plummets like a lead balloon above 60 mph and in fact usually I cruise it at 52-55. Would it benefit from MORE rpms via a gear DOWN?
