In article <F271vPEkGhAj5p1Fjxe00000d6d@hotmail.com>, Greg Rowe
<growe58@hotmail.com> writes
>Hi, Mike.
>
>According to a reprint of the March 1975 test by Autocar Magazine:
>
>Mph per 1000 rpm
>
>OD Top 22.6
>Direct Top 18.0
>OD 3rd 16.2
>3rd 12.9
>2nd 8.3
>1st 5.1
>
>So, 3000 rpm in 4th would be 18 X 3 which equals...uh... 54 Mph? So
>the program you've discovered is pretty close.
And it appears that my calculations were valid as well. Damn: my
speedo is reading 15% low. That could get me into a lot of trouble...
>
>BTW, there are no frictional or wind resistance losses associated
>with engine speed/road speed relationships. If you double engine
>speed, you will double road speed (there is a very small factor
>associated with the tires ballooning at speed due to centrifugal
>force, but this can be ignored).
Thanks for clarifying that.
>
>Another way that may be easier to calculate true speed, is to
>put a drop of paint on your tires and roll the car. Measure
>how far about the dots are and you can easily calculate how
>many times your wheel turns in a mile. Multiply that by 3.63
>(your final drive ratio) and that will be engine speed at
>60 mph.
Good idea. The consensus seems to be that I should get 18 mph per 1000
rpm, so I shan't bother with this cross check.
How do I calibrate my speedo?
ATB
--
Mike
Michael Hargreave Mawson, author of "Eyewitness in the Crimea"
http://www.greenhillbooks.com/booksheets/eyewitness_in_the_crimea.html
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