Tom, Ed, all..
not withstanding what Tom quoted, My towncar gets far better millage at
75-80 mph than it does at 55 or 65. I went to Texas recently for a
family reunion and the average speed between there and return here,
including the low speed in town driving there was 70 mph and the fuel
mileage was 26.5 mpg. Not as good as Ed's 'vette but then again I have
a sofa on wheels. To me the issue revolves around the torque peak of the
motor. as that is where the best BSFC comes in (isn't that right, Dave?)
so riding near that is best for millage provided the motor has the
beans at that speed to pull the gears and against aero and rolling
resistance forces. So many factors need to be taken into account. I
drove back from LA one weekend and there was a tail wind of about 25
mph...my mpg shot up to 33 mpg just from not having to fight that small
amount of wind. I never use the cruise control because it is always
applying the throttle up and down and each time enriching the fuel. So I
drive level up hill and foot off and coast down as long as my speed is
near the peak. of engine efficiency.
mayf
Tom Bryant wrote:
>Ed,
>
>I don't doubt that what you say is correct. There are always exceptions. I
>don't claim to be a "Rocket Scientist", I was referring to a July 2007
>article from Motors Magazine by Mike Dale, "Meddle With the Pedal:
>Electronic Throttle Control." This article was part of recent Instructor
>Training that I attended for the CA Smog Program.
>
>Quote.."Given normal gearing, the peak efficiency point for a vehicle turns
>out to be around 55 mph. The double-nickel speed limit was not chosen
>randomly, but rather with an eye to best results for fuel economy for the
>average vehicle. For a given distance traveled, fuel economy tapers off at
>both higher and lower speeds. Holding a constant speed is an advantage, as
>it avoids both the extra fuel needed for acceleration and the increased
>emissions that often result from deceleration.
>
>Not surprisingly, the sweet spot of engine efficiency is also the sweet spot
>for emissions output."....This is a very interesting article that can be
>found on line by going to http://www.motor.com/article.asp?article_ID=1179
>
>Tom, Redding CA - #216 D/FCC
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