Quote:
Originally Posted by christofoo
Phil, is there a mistake in your 32MPG figure? I know you're using a formula I'm not familiar with, so I'm just asking you to double-check, but I think you should get more MPG with a 2.0L under that road load and speed. In principle, with a lean-burn and proper gearing or somesuch, the upper limit for Cd=.125 A=~20sqft should be a whopping 60+ MPG at 100 MPH.
More to the point, if you get 32MPG at 31BHP at 75MPH, you should get 43MPG at 31BHP at 100MPH, all other things being equal.
But maybe I just didn't follow along.
EDIT: I would totally pay a couple $k premium to get access to a 100MPH-rural-in-good-weather-and-daytime freeway system (and I would even drive that fast once in a while), knowing it would double as an ultra-MPG commuter. I think it's a slick policy angle for aerodynamics.
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Yep,we can do much better,but the premise of the blog was that with 1996 engine and powertrain efficiency,aerodynamics alone could deliver the numbers.(this really was the whole point of the blog)
If you extrapolate the HONDA power curve for 75 mph,you can read the Road Load power directly.This is the 'baseline.'
Subtracting the Rolling-Resistance power component at 100 mph (read directly from the curve) from the 75 mph Road Load yields the remaining power available for aero.(with gear-matching,the engine will see an identical load as at 75 mph and will operate at the same BSFC and deliver the same economy)
Using this value,we solve for the Cd which can satisfy this condition.
Cd 0.125 falls out of the equation.
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With Toyota's current Phase-II GDI-turbo-intercooled technology, with 43% thermal efficiency,we have the efficiency of a diesel engine,only lacking the extra 11% chemical energy which diesel packs into each gallon/liter.
Add 2013's improved low-rolling-resistance tires and we push the numbers even higher.
Dr.Paul MacCready estimated 400 mpg for the 1987 GM SunRaycer of same drag coefficient,of course with much smaller frontal area,greatly reduced mass,and 'normal' highway velocity.
This is the sort of thing which led to the idea for the 'Template,'which shares similar architecture with the SunRaycer.