Metro aerodynamics - Page 23 - Fuelly Forums

Click here to see important news regarding the aCar App

Reply
 
Thread Tools Display Modes
 
Old 02-20-2007, 05:57 AM   #221
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
Quote:
Originally Posted by Peakster View Post
Clearly aerodynamics play a big role even at low speeds since the table and chairs only weigh 100 pounds at most.
I get the feeling that many people mistakenly assume that
__________________

MetroMPG is offline   Reply With Quote
Old 02-20-2007, 09:32 AM   #222
Tuggin at the surly bonds
 
Silveredwings's Avatar
 
Join Date: Apr 2006
Posts: 839
Country: United States
Quote:
Originally Posted by MetroMPG View Post
Even at just 20 mph, 1/3 of the total power (about 1.2 hp) required to move a Metro goes to overcoming aero losses. 1/5 of the power at 15 mph.
Is that from a source of empirical data on the metro? I'd really like to see more of that curve.
__________________

__________________
Reality is merely an illusion, albeit a very persistent one. - Albert Einstein
Silveredwings is offline   Reply With Quote
Old 02-20-2007, 09:54 AM   #223
Registered Member
 
Peakster's Avatar
 
Join Date: Sep 2006
Posts: 467
Country: United States
Wink Ok, while you two talk numbers,

I'm going to do a little test run today. I'll drive west to Moose Jaw, Saskatchewan on the Trans Canada Highway (very straight an flat road). First run with hatch up:

Attachment 214

I'll record MPG at different speeds (let's go with 35, 45, 55, and 65mph) and the second run with hatch closed:

Attachment 215

(again recording MPG at those same speeds).

I'm interested to learn what percentage MPG loss/increase there is to each speed. (this has made me wonder for a while since MetroMPG got a 2.3% MPG increase when removing mirrors @ 55mph in mild temperatures, while I got a 2.23% increase when driving 70mph in really cold temperatures, without mirrors).
Attached Thumbnails
Click image for larger version

Name:	IM001260.JPG
Views:	475
Size:	73.9 KB
ID:	187   Click image for larger version

Name:	IM001262.JPG
Views:	279
Size:	71.8 KB
ID:	188  
Peakster is offline   Reply With Quote
Old 02-20-2007, 11:34 AM   #224
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
Wow. Ambitious, Peakster. I'm guessing it's not -25C today.

I'm also guessing you're going to see a dramatic drop in FE. My WAG = -20%. (Better put a stick under the hatch to hold it open!)

SW: it's
MetroMPG is offline   Reply With Quote
Old 02-20-2007, 03:57 PM   #225
Registered Member
 
Peakster's Avatar
 
Join Date: Sep 2006
Posts: 467
Country: United States
Quote:
Originally Posted by MetroMPG View Post
Wow. Ambitious, Peakster. I'm guessing it's not -25C today.

I'm also guessing you're going to see a dramatic drop in FE. My WAG = -20%. (Better put a stick under the hatch to hold it open!)

SW: it's theoretical data: http://www.metrompg.com/tool-aero-rr.htm

EDIT: Did you put the mirror back on? Or is that an older pic?
20% was a good guess... for 40mph . Take a look at the video and see the difference for yourself.

BTW, I've had the mirrors back on the Geo for weeks now. The plastic covers for the holes in the door froze and fell off and it looked dumb. I'll make better plastic covers when the weather gets a bit nicer.

Edit: *gasp* I forgot to put the gassavers link on the video
Peakster is offline   Reply With Quote
Old 02-20-2007, 04:04 PM   #226
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
Can't! I'm on dial-up at the moment
MetroMPG is offline   Reply With Quote
Old 02-20-2007, 06:20 PM   #227
Registered Member
 
Peakster's Avatar
 
Join Date: Sep 2006
Posts: 467
Country: United States
Here's the little test in a nutshell:

Temperature: -4*C
Winds: south @ 11km/h (I was driving west)
Cruise control was used to maintain speeds
Each mpg reading was taken after 2 miles of travel
Route:
Attachment 216

Hatch closed:
73.6 mpg @ 35 mph
62.9 mpg @ 45 mph
49.2 mpg @ 55 mph

Hatch open:
62.4 mpg @ 35 mph (15.22% mileage loss)
48.2 mpg @ 45 mph (23.37% mileage loss)
34.4 mpg @ 55 mph (30.08% mileage loss)

Those are huge numbers for something as simple as opening up the rear hatch. What do you think my Cd was when it was open? 0.44? I'm now beginning to believe that small aero mods to these little cars (such as mirror removal, wheel skirts, etc) would help FE in more than just highway travel.
Attached Thumbnails
Click image for larger version

Name:	geo exp 2.1.gif
Views:	356
Size:	12.4 KB
ID:	189  
Peakster is offline   Reply With Quote
Old 02-20-2007, 07:32 PM   #228
Registered Member
 
The Toecutter's Avatar
 
Join Date: Mar 2006
Posts: 612
Country: United States
Send a message via AIM to The Toecutter
At 25-30 mph or so is when aero losses become as large as rolling losses on flat ground. So even at those speeds, aero mods should in theory have significance. But this is steady speed driving as opposed to stop and go driving. Stop and godriving will make weight and rolling losses a much larger factor than they are in steady speed driving.
The Toecutter is offline   Reply With Quote
Old 02-21-2007, 03:41 AM   #229
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
Quote:
Originally Posted by Peakster View Post
Those are huge numbers for something as simple as opening up the rear hatch. What do you think my Cd was when it was open? 0.44?
(I think it's in my "favourite GS links in my sig.)
MetroMPG is offline   Reply With Quote
Old 02-21-2007, 11:19 AM   #230
Registered Member
 
Peakster's Avatar
 
Join Date: Sep 2006
Posts: 467
Country: United States
Quote:
Originally Posted by MetroMPG View Post

@ 88 km/h (54.7 mph) ...
  • Just adding (empty) roof racks changed my mileage by -7.0 mpg / -12.7%.
    .
  • Putting my mountain bike up there on the rack absolutely destroyed the mileage: -15.1 mpg / -27.3%

And unfortunately, it's likely the negative effect of roof-top carrying is more pronounced on smaller, less powerful cars.
Holy smokes. These results make me want to find another SG compatible metro, chop the top off and see what crazy MPG numbers show up.
__________________

Peakster is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is your vehicle set correctly? DTMAce General Fuel Topics 1 03-17-2010 05:21 AM
fuel economy question Creamycaesar General Fuel Topics 19 02-08-2010 07:37 AM
p07 ECU $15 Matt Timion For Sale 4 08-27-2006 11:25 AM
I will be bike riding across Iowa kickflipjr People Powered 11 08-02-2006 03:22 PM
Some glue that won't melt when it gets hot? SVOboy General Maintenance and Repair 16 08-01-2006 07:15 AM

» Fuelly iOS Apps
Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 05:56 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.