From: Alistair Bell <albell@uvic.ca>
> >You would actually need all terms in the polynomial. >Contributiong to the force is: >0th order: static friction. >1st: surface friction in laminar flow, tire and bearing friction etc. >2nd: Turbulent flow. >The "fitted curve" on my graph is done this way. > Ahh, sorry, once again I jumped the gun! I have to admit that i didn't look at your "methods" on your webpage (writing this at home using a 10year old SE/30, good for mail but not so good at web browsing, that'll have to wait 'tll i get to work). Anyway, I assumed that the drag was calculated from actual "road" measurements, not a calculated value. The road test data is used to find the coefficients in the model. The raw data was also plotted, but of course only gives a few point values. Here are the links if you forgot them: A power curve: http://www.cs.rochester.edu/u/jag/vw/engine/diesel1.9/Diesel1.9l_12_98.gif Torque curve: http://www.cs.yale.edu/~jag/vw/engine/diesel1.9/Diesel1.9lTorque_12_98.gif Drag curve: http://www.cs.yale.edu/~jag/vw/engine/diesel1.9/WestyDrag_12_98.gif Tire friction is (somewhat) significant. After some (a lot of) search you can find coefficients for this from the major tire manufacturers. I posted some years ago, but forgot the details. Think that the linear term is about 10kW or maybe 10 hp at 60 mph. Not dominating, but not insignificant either. /Martin |
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