Engine and Aero Efficiency

[jamesqf]

Originally Posted by Old Mechanic

If 4.5 hp can propell my 200 pounds at 40 MPH and 150 MPG, why would you need more than the 25 HP I will have in my 3 wheeler at 1100 pounds...

For climbing hills, and accelerating. As others have pointed out, with decent aero it doesn't take much power to cruise on level roads. IIRC 65 mph takes less than 17 hp in my Insight.

...versus the 50 cc super cub at 350 pounds, me included in both even including another passenger (not on the super cub).

50 cc? Maybe if you have a big RC model of one. The (stock) Super Cub has an O-235 engine or larger.

[user removed]

One of these.

regards
Mech

[Frank Lee]

Originally Posted by jamesqf

50 cc? Maybe if you have a big RC model of one. The (stock) Super Cub has an O-235 engine or larger.

[chumly]

Originally Posted by Old Mechanic

One of these.

regards
Mech

I'd rather have the one that can fly!

[Frank Lee]

I want one of each.

[aerohead]

Originally Posted by jamesqf

For climbing hills, and accelerating. As others have pointed out, with decent aero it doesn't take much power to cruise on level roads. IIRC 65 mph takes less than 17 hp in my Insight.



50 cc? Maybe if you have a big RC model of one. The (stock) Super Cub has an O-235 engine or larger.

Could I ask where that information came from?

[jamesqf]

Originally Posted by aerohead

Could I ask where that information came from?

Which? The info about the Super Cub came from Wikipedia (and originally from memory). For the Insight, it came from calculations. Don't have exact figures to hand, but there is a long grade on a highway near here that descends a couple of thousand feet. The Insight will hold about 65 mph down that grade, with no throttle and only a bit of regen. From that, it's easy to compute approximately how much energy is generated by lowering the weight of the Insight that distance. Time the descent, divide (because power is energy/time) and convert to horsepower.

PS: Now that I think back on it, it was probably rather less than the 12-17 hp I calculated, since think I had the car in gear. Be interesting to try it again, with a GPS to track elevation change & time.