Quote:
Originally Posted by MetroMPG
Thanks, Phil! It should be easy to sell. It really is a nice car.
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Not worth 30 gallons of gas for a cardboard + coroplast boat tail that won't fit your car properly! DIY, baby.
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I posted the fancy test graphs and raw numbers in post #4 (which I had 'reserved' for that purpose when I started the thread).
You'll see in the first graph something that we haven't talked much about : the Kammback section on its own apparently made no difference vs. a bare back end. Very strange, this Civic. (More likely: not optimal, my handiwork.) |
I caught the comment but wanted to wait 'n see how things shook out.
At least one member has shared an example of a notchback with lower drag than a hatchback/Kamm style car.
Chrysler ran into something like this with the Daytona.At the time,they considered a 12-degree roofline to be a proper 'fastback'.(Kamm had tossed out a 10-degree rule of thumb for HOT ROD Magazine,but didn't follow his own rule)
With the Dodge,we see that an 18-degree slope notchback comes in at lower drag than the 'fastback.' The flow on a notchback is governed by a delicate dance between the backlight,C-pillars,boot,and body sides.
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The template is based upon a body of revolution where the sides and roof begin their curvature at the same point on the body,and the sides are indistinguishable from the roof as far as contour goes.
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Looking at the views of the CIVIC I notice that the roof hits its max. camber point between the door handles as we see it,but the beltline,at the base of the greenhouse is still rising all the way to the taillight lens,putting its max camber point there.
This would suggest that the tail for the main body section would have to start from zero down-slope at the rear transom,with no slope at all,but with whatever plan-taper Honda already had.Just like I had to do with the T-100.
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The CIVIC's roof would be like Jaray's combination form cars,with a 'faster' greenhouse than the main body.
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The tricky part is that without a rolled edge over the taillight void (as I did with foam and Plexiglas with the T-100) we're asking the air to camber downwards and inwards at this 'edge' without a structure to guide the transition.
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I've made a bunch of images of the CIVIC to toss over in my head and my thoughts go to a 'slower' tail on the main body,using the template at the top of the taillight as a guide,then let the 'stinger' from the greenhouse die into it,blending,as on the VW XL1 car.
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Without a plan-view it's
hard to tell,but it seem like the 'stinger' could be a little more aggressive in plan-view,it's essentially perfect in side elevation.
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Seems like we were very 'close' and I have no idea how the engine behaves.
AeroStealth found that between say, 55-70-mph,the F-150 gets better mpg with the AC on than without,after Brett's modifications were added.Then above 70-mph,it's better to lose the AC as far as mpg goes.Which suggests that the 'sweet-spot' for BSFC IS affected by the streamlining.
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My ignorant suspicion is that you lowered drag more than the mpg would suggest,and that the bugaboo is with the engine mapping/gearing/load.
If you were commuting between Austin,TX and San Antonio on the 85-MPH Texasbahn toll road,no other CIVIC would be able to get anywhere near your mpg.
