Dat2000srl@aol.com wrote:
>
> Perhaps Mike is correct about the efficiency and torque, etc., But I would
> think the Nissan engineers took this stuff into consideration when they
> decided how to gear the car. Or do you suspect they just threw the 5th gear
> in there as a feature? Maybe someone out there knows the answer, but I
> believe 5th is most efficient at highway speeds. I have owned several cars
> with a 5th gear, they all seemed more efficient in 5th. even a dat B-210, it
> would get 50+ mpg in 5th at 60 mph, and I know that was not even close to the
> power band, the engine was only revving about 2000 rpm. There was a test on
> the efficiency of the B210 and I remember the result were as such:
> 70 mph.....5th gear......31 mpg
> 60 mph.....5th gear......42 mpg
> 50 mph.....5th gear......51 mpg
> 40 mph.....5th gear......62 mpg
> 30 mph.....5th gear......70 mpg
> This was published in Car and Drive in 1980, I don't remember the month, But
> I had the car at that time and found their finding very accurate. Of course
> the B210 is not a roadster so your results may vary!
> Larry
> 69 2000
> Ravens country
This mixes several data into one pie and obscures the results. With any car,
once you get past a certain speed, the cd will have the largest affect on
mileage. Gearing will override that only at the very extremes of the bell curve.
I doubt that the car got any better mileage at 20 in 5th gear, because by that
speed gearing was overriding the aerodynamic drag. Had they done this test on a
chassis dyno where aerodynamic drag was factored out, then I believe the results
would have been very different. Also a test at the same speed in various gears
would have at least given you some idea what effect the gearing had on mileage.
--
Marc Sayer
82 280ZXT
71 FJ510
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