Quote:
Originally Posted by orange4boy
I had disappointing results with the mpg and seat of pants from the new back. I had thought the angles were wrong. Top was 15-17 and sides were 15-20. I changed to 12 top and 12 sides but the van still seems to be sluggish on coastdown. It was much better with just the short extensions. It's possible the cooler weather is affecting the results. Just how much difference is there in air density between 85F to 70F? Or could the half shell create some massive vortex, increasing drag?
Of course it could be a dragging brake or some other increased friction like a toast bearing. I guess I should take the sucker off and try it that way.
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With just the 1/2 shell, it's predictabilty lies in the realm of the netherworld.My intuition suggested benefit,but no science to support it.----------- No books with me here so I cannot address the air density question,sorry.Falling temps will also affect all your lube viscosities and wheel bearing grease and tire RR.Lots of variables which is really bad for testing.------- If I lived next door,I'd help you fabricate sides and bottom for a re-test,back -to-back,same day,with and without,to minimize those variables.