Quote:
Originally Posted by donee
Hi All,
Well, the reason I want to improve the Cd of the Prius, besides what I posted on PC, is that Excell, Hobbit et al have found what they call SHM, or Super Highway Mode. With a stock Prius, the car can hold this up to about 50 mph. At these speeds, in SHM, the Prius is getting 60 to 75 mpg demonstrated. With reduction in drag force, maybe SHM can be used at 62 to 64 mph (which is the max engine un-fired, still rotating speed) and is what the dictates of the proletariat on Chicagoland freeways pretty much force as a minimum crusing speed. Besides, I can't Drive 55.
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Donee,
I was thinking the same thing about SHM, perhaps being able to extend it by a few MPH by reducing drag. I have done some testing and found that for my Prius, on a fairly level surface, I can maintain SHM up 47 MPH at just over 71.8 MPG with temps in the mid 50's F. Anything above that and the FE drops quickly.
Just to give you some idea on how the low the Cd would have to be to achieve SHM at higher speeds. Assuming that SHM can be maintained up to 47 MPH in my case, I calculate 7.42 HP is required. If I increase the speed and maintain 7.42 HP:
- At 47 MPH, Cd = 0.260
- At 50 MPH, Cd = 0.205
- At 55 MPH, Cd = 0.142
- At 60 MPH, Cd = 0.099
- At 65 MPH, Cd = 0.070
I would be happy with 0.14 I think.
