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Re: [GMCnet] Keeping it Real, 8 to 10 mpg [message #172646 is a reply to message #172628]

Fri, 08 June 2012 20:03

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma:

Senior Member

G'day,

Many years ago when I was building hot rod Harleys over in Hong Kong I
worked with an old hot rodder named Jerry Branch. He was THE go to guy for
Harley heads.

We got to talking about the coefficient of drag (CoD) and how it affects
Harleys. He noted that every little gee-gaw (his words) hanging off the bike
into the air stream created turbulence and that he figgered running a stock
Harley down the road was like moving a 4 x 8 sheet of plywood through the
air stream.

A GMC doesn't have as much "stuff" hanging off the body shell but there's
enough to cause a fair amount of turbulence when one considers: the mirrors,
wind wings (if you installed them), roof A/C(s), TV antenna, satellite
antenna, Fantastic Fan vents, pods, luggage rail / ladder, etc.

I vaguely remembered that the CoD for the GMC was 0.3 something. I did a
Google search and found the following in the Wikipedia entry for GMC
Motorhome:

http://en.wikipedia.org/wiki/GMC_motorhome

GMC motorhomes in good condition and in proper tune are as efficient as
similarly powered modern motorhomes, despite the use of computer-controlled
engines on the latter, and typically see 9 to 11 miles per US gallon (21 to
26 L/100 km; 11 to 13 mpg-imp) of regular unleaded fuel. GMC Motorhomes
tested via a wind tunnel were reported to have a drag coefficient of 0.31,
which is typical of modern sedans (although offset by the large frontal
area).

I think Bill Bryant has the wind tunnel model and IIRC it is smooth as a
gut; NOTHING hanging off it.

At any rate I reckon that the CoD has a much greater effect on GMC mileage
than anything else.

Regards,
Rob "once again demonstrating an acute grasp on the obvious!" M.�

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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[Message index]

		[GMCnet] Keeping it Real, 8 to 10 mpg By: Mr ERFisher on Thu, 07 June 2012 16:38
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Harry on Thu, 07 June 2012 16:43
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: kelvin on Thu, 07 June 2012 16:50
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: george beck on Thu, 07 June 2012 17:31
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: ljdavick on Thu, 07 June 2012 17:36
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: jhbridges on Thu, 07 June 2012 18:39
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Harry on Thu, 07 June 2012 18:45
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: George Beckman on Thu, 07 June 2012 19:09
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: RF_Burns on Thu, 07 June 2012 17:05
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: kelvin on Thu, 07 June 2012 17:08
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: ljdavick on Thu, 07 June 2012 17:41
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: USAussie on Thu, 07 June 2012 18:56
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: stick miller on Thu, 07 June 2012 19:12
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: mannystrans on Thu, 07 June 2012 23:19
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: hnielsen2 on Thu, 07 June 2012 19:46
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Harry on Thu, 07 June 2012 23:08
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Chr$ on Fri, 08 June 2012 00:58
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: larry.whisler on Fri, 08 June 2012 08:28
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Steven Ferguson on Fri, 08 June 2012 07:15
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Byron Songer on Fri, 08 June 2012 08:09
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: kelvin on Fri, 08 June 2012 10:53
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: roy1 on Fri, 08 June 2012 12:13
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Jim Galbavy on Fri, 08 June 2012 17:09
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: kelvin on Fri, 08 June 2012 17:19
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: jaholland on Fri, 08 June 2012 18:46
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Ray Erspamer on Fri, 08 June 2012 21:04
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: USAussie on Fri, 08 June 2012 20:03
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: mike miller on Sat, 09 June 2012 10:57
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: mike miller on Sat, 09 June 2012 11:01
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: USAussie on Sat, 09 June 2012 19:39
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: mike miller on Sat, 09 June 2012 20:01
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: USAussie on Sat, 09 June 2012 20:49
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: mike miller on Sun, 10 June 2012 00:31
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: USAussie on Sun, 10 June 2012 01:52
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Kudzu on Fri, 08 June 2012 21:26
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: Ray Erspamer on Fri, 08 June 2012 21:29
		Re: [GMCnet] Keeping it Real, 8 to 10 mpg By: JohnL455 on Fri, 08 June 2012 22:43

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