Quote:
Originally Posted by Multiades
It would be pretty hard to find the optimum speed to drive at for highway mileage, but assuming you were able to reduce Cd on your car enough that aero drag was less of an issue, I bet putting it near the center of the sweet spot on that BSFC graph would be about right.
55-65% Load (perhaps 18in/Hg vacuum) at 2500rpm might be ideal.
With your actual tires, speeds should be as follows:
Code:
RPM MP2 MP3
2000 58 48
2100 61 51
2200 64 53
2300 67 56
2400 70 58
2500 73 61
2600 76 63
2700 79 65
2800 82 68
2900 85 70
3000 88 73
I somehow doubt you can do 73mph efficiently in a car that isn't shaped like a needle -- looks like the MP3 gear might be better in some ways for that. The BSFC "sweet spot" seems to extend down to 2000 with room to spare, so maybe your best mileage will be at 60ish.
If the car feels absolutely powerless on flat highway at 2k that's probably too low. Aero would help.
50mph is probably too slow though.
What, in case you have to go really fast because your wife is in labor? 
-Chris |
I can tell you that unloaded the car has a modest amount of usable accel from 50mph in 5th. On ramps are FE killers. Loaded full of family you pretty much set the throttle to 20% and wait for accelleration to occur.
From a strictly efficiency perspective the engine is most eff at 2500rpms. My understanding(small brain here) is at max efficiency its producing the best ratio of BTU's used vs work produced. Unfortunately at 73mph a lot of work is wasted on aerodynamic load.
I believe the best FE is attained around 39-42mph for the MP2 equipped saturn. I have one tank at 62mpg, where at didn't really exceed 50 mph.