Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 02-21-2010, 11:01 PM   #1 (permalink)
Master EcoModder
 
bondo's Avatar
 
Join Date: Jan 2008
Location: Arkansas
Posts: 279
Thanks: 90
Thanked 238 Times in 89 Posts
Aerocap Performance (Why are we seeing wide variation in reported MPG savings?)

In the past two months a couple of people here have built aerocaps and have posted some short term test results. There has been an A-B-A test posted by one of them and this data has been posted on the home page of ecomodder as being conclusive, a 4% increase in fuel efficiency.

In all fairness, I have made claims on the other end of the number line, a 20% increase in fuel efficiency. I should have reported this percentage as being able to achieve as high as a 20% increase in fuel efficiency, which I truthfully have on a few occasions. I am sure if I were to perform an A-B-A test this number would not hold and my percentage would be lower.

The wind tunnel testing I have had done on the Aerolid is all I can offer. In the A2 wind tunnel test the Aerolid achieved a delta Cd of -0.062. This test was with the lid on my 2006 F150 which Ford says has a baseline coefficient of drag of .42. I plan to do an A-B-A test but not until the weather warms up.

So as I try to get the Aerolid to market, the incorrect 4% fuel efficiency improvement which greets one who signs onto ecomodder and sees Fubeca's A-B-A result, which in all fairness to Darin, I feel is extremely flawed due to atmospheric conditions at the time of the test. The following information was compiled by Darin in 2007 in a report on how cold weather effects fuel efficiency and he claims aerodynamics are effected by the density of cold air.

http://ecomodder.com/forum/showthrea...leage-220.html

Within this thread you will find a link to an earlier thread at MetroMPG.com in which data he compiled is presented showing the declination in fuel efficiency as air temperatures lower. He also goes further in reason number 9, Aerodynamics, how aerodynamic drag increases by 2% with every 10 degree drop in temperature.

I owe Darin and and the good folks here at ecomodder a great amount of thanks for getting the Aerolid alot of exposure. Inversely, a reported 4% gain in fuel efficiency is all an aerocap will get you is not the kind of exposure you want if you are looking to get an aerocap to market.

I cannot offer an A-B-A result yet. All I can offer are the two wind tunnel tets which were done on the Aerolid. I can also offer my road test results which showed a solid 15% increase in fuel efficiency during the two years I ran the Aerolid on my 2006 F150. Check out round.boater's fuel log since he got his Aerolid in May of 2009.

So Darin let's work together to get closer to the truth. Fubeca and Chaz have worked hard on their lids and I hope they do not get dismayed by poor fuel efficiency results due to cold weather. If they can hold out until spring, they will be pleasantly surprised.

Bondo

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 02-21-2010, 11:07 PM   #2 (permalink)
Master EcoModder
 
Big Dave's Avatar
 
Join Date: Jan 2008
Location: Steppes of Central Indiana
Posts: 1,319

The Red Baron - '00 Ford F-350 XLT
90 day: 27.99 mpg (US)

Impala Phase Zero - '96 Chevrolet Impala SS
90 day: 21.03 mpg (US)
Thanks: 0
Thanked 186 Times in 127 Posts
The wide variation in results puzzle me. My results were more in line with Bondo's and my lid is crude, crude, crude.

Methinks we have a wide variation in test methods. Testing in mid-winter invites wide variability.
__________________
2000 Ford F-350 SC 4x2 6 Speed Manual
4" Slam
3.08:1 gears and Gear Vendor Overdrive
Rubber Conveyor Belt Air Dam
  Reply With Quote
Old 02-22-2010, 11:53 AM   #3 (permalink)
Pickup Fuel Meiser
 
Join Date: Apr 2009
Location: Madison, WI
Posts: 32

Blackline - '09 Nissan Frontier King Cab SE V6

Jetta - '11 Volkswagen Jetta Sportswagen TDI
Thanks: 1
Thanked 1 Time in 1 Post
Bondo, if we are to go by your wind tunnel test, if its a .06 decrease in drag from .42, does that mean a 14% improvement in aerodynamics?

I'm looking forward to buying an Aerocap for my 2009 NISSAN FRONTIER, eh hem, even single-digit improvements would be a lot more than I can accomplish with wheel discs and grill covers.
__________________
Frank
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
RIDE A BIKE!: "If by tomorrow, every gas guzzler on the road were replaced by Priuses, we would still have the same gridlock, accidents, deaths, injuries and the same pressures to put more asphalt, strip malls and subdivisions." --Thomas Smart: SuperCommuter


  Reply With Quote
Old 02-22-2010, 04:40 PM   #4 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,237

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
Thanks: 3,796
Thanked 6,655 Times in 3,447 Posts
Hi Brett -

First: let me say I have huge respect for what you're doing and I hope you become a zillionaire because of your cap. I praise it to everyone I talk to about pickup truck aero.

The Cd info you provided is fantastic:

Quote:
Originally Posted by bondo View Post
The wind tunnel testing I have had done on the Aerolid is all I can offer. In the A2 wind tunnel test the Aerolid achieved a delta Cd of -0.062. This test was with the lid on my 2006 F150 which Ford says has a baseline coefficient of drag of .42.
Quote:
let's work together to get closer to the truth.
Regarding Fubeca's number, don't forget we have to compare apples to apples, and we're not in this case. This is important:

1) He tested at a much lower speed than you did! At 55 mph, this is reflected in the smaller % difference he measured vs. the % difference you will see at 75 mph. If he had tested at a slower speed it would have been even lower (less than 4%), and if you had tested at 85 mph, your % results would have been even greater.

2) He's using a different truck,

3) His cap design is different from yours

4) Neither your or Fubeca's tests is "lab quality", so let's not get hung up on the decimal points, if you know what I mean.

All of these things make it impossible to directly compare his results to yours. (Also I don't think the home page suggests that all caps are created equal or that everyone should expect only 4% from an aeroshell.)

Unless you're testing the same truck at the same speed(s), in the same conditions, it's apples & oranges.

But we can work with your numbers:

If we plug the values for your truck into the aero/rolling drag formula for calculating power requirements across a range of speeds, here's what we find:

Using your vehicle (Brett's 2006 F-150)...

Weight: 4,840 lbs
Base Cd: 0.42
Cd with aeroshell: 0.358
Frontal area: 33 sq. feet (* this is an estimate: I couldn't find the value online, and EcoModder's CdA list has a value of 31.5 sq. feet for the previous generation 2004 F150 Lightning, lowered and probably slightly smaller. For comparison, a 2002-2008 Ram 1500 is listed at 35.1 square feet.)
Crr: .0125 (estimate)

Based on the Cd difference (and adding 150 lbs - est. - for the aero shell), let's calculate power requirements (in Watts) and look at the % differences to travel at 55 mph and 75 mph, at 25C and -10C (taking air density changes into account):

  • Stock truck Cd 0.42 (open bed)

    @ 30 C / 86 F on summer fuel
    (click the links to open the tool with all values entered)
    55 mph requires 17,758 Watts (~21.7 MPG US)
    75 mph requires 37,271 Watts (~14.1 MPG US)

    @ -10 C / 14 F on winter fuel

    55 mph requires 19,452 Watts (~19.5 MPG US)
    75 mph requires 41,566 Watts (~12.4 MPG US)
  • With aeroshell Cd 0.358 (plus 150 lbs - est.)
@ 30 C / 86 F on summer fuel
55 mph requires 16,319 Watts, 8.1% better than stock in same conditions (~23.6 MPG US)
75 mph requires 33,381 Watts, 10.4% better than stock in same conditions (~15.8 MPG US)

@ -10 C / 14 F on winter fuel
55 mph requires 17,763 Watts, 8.6% better than stock in same conditions (~21.3 MPG US)
75 mph requires 37,042 Watts, 10.9% better than stock in same conditions (~14.0 MPG US)
__________________
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following 3 Users Say Thank You to MetroMPG For This Useful Post:
bondo (02-22-2010), gascort (02-24-2010), mjboks (02-22-2010)
Old 02-22-2010, 04:41 PM   #5 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,237

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
Thanks: 3,796
Thanked 6,655 Times in 3,447 Posts
Quote:
Originally Posted by Big Dave View Post
Methinks we have a wide variation in test methods. Testing in mid-winter invites wide variability.
Big Dave, I think you're right on both points.
__________________
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 02-22-2010, 05:31 PM   #6 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 13,020
Thanks: 20,857
Thanked 6,362 Times in 3,950 Posts
numbers

Brett,I come up with same modified Cd as Darin ( 0.358 ).
From Kelley & Holcombe at GM in the 1960s,they'd say that the 14.8% drag reduction would net you a 7.4 % mpg increase at 55-mph,and 8.8 % at 70 mph.
These relationships assume a constant BSFC which in the real world does not exist.
The other context,is that when this research was conducted,pickup Cds were in the neighborhood if 0.55.
In 1988 when Texas Tech published their paper,it was right after GM's introduction of their body in white,all-new pickup,which cut the Chevy and GMC drag from Cd 0.535,to 0.45.
In Tech's paper,they mention that the aeroshells benefit can be matched by a re-design of a pickup.
It's probable that modern trucks may not respond to aero mods as was seen with the F-150 tested by Tech.
The only claim they can make, is that an F-150 of that era,would see a 20 % drag reduction with the aeroshell.And this would be under SAE test protocals,with results normalized to standard temp and pressure,something very difficult to carry out.
Your shell mirrors the architecture of the aeroshell so closely,and respects parameters understood very well,for going on a century now,that as far as 'performance' your shell would have to fall at the high end of the curve.It's just that good.
To learn the most from our mods,we would have to do as comprehensive as testing as SAE.Short of that,we're going to see some 'scatter'.
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
bondo (02-22-2010)
Old 02-22-2010, 05:43 PM   #7 (permalink)
Master EcoModder
 
bondo's Avatar
 
Join Date: Jan 2008
Location: Arkansas
Posts: 279
Thanks: 90
Thanked 238 Times in 89 Posts
I learned something new today.

Thank you Darin for taking to time to post very imformative information that I had not calculated. I suffer from being extremely right brained and my math skills are lacking. I wish to thank you for telling people about the Aerolid also. One truth is that financiual gain is a motivator to me but it is not the only motivating factor I have to see the Aerolid go to market. I would love to create jobs for others and a job for myself. After being out of work for 15 months with no unemployment, you realize the value of a job.

Again, I have learned something today and it all hinged on divulging the delta Cd number. I wish now I would have done this much sooner. The points you make about the differences in the aerocap construction, speed and truck type between my truck and Fubeca's definitely would produce a variance in the test results.

I agree also with Big Dave on how we do have a wide variation of test methods which do produce wide variation.

What would be so cool is for us all to get together at the A2 wind Tunnel for some testing. They are a great bunch down there and they were just charging about $350.00 an hour for testing which isn't bad. That is how I could afford it. We could fugure out what kind of test we would want to do, not just, pickups, and get to meet each other and have alot of fun too!

Again, thank you for running the numbers for me on my truck with and with out the Aerolid and with a variance in temperature. I have learned alot in my years in design but one thing I found out is you can never know it all, you learn form others. As this post is titled, I learned something new today.

Thanks again,

Bondo (Brett)
  Reply With Quote
Old 02-22-2010, 05:59 PM   #8 (permalink)
Master EcoModder
 
bondo's Avatar
 
Join Date: Jan 2008
Location: Arkansas
Posts: 279
Thanks: 90
Thanked 238 Times in 89 Posts
Thanks Phil!

I appreciate you running the numbers on my truck also. You and Darin both have a better developed left hemisphere of the brain than I. I must then contribute the higher percentage of fuel efficiency I experience in my truck, which tends to be much greater than 8.8%, to my driving habits.

The human factor is a very important element to the operation of any machine designed to be operated by a human. In that operation, certian controls can be excercised to achieve a desired result. This result, though influenced by the human factor, is still a real world result, though it may not be by the numbers.

Thanks,

Bondo (Brett)
  Reply With Quote
Old 02-22-2010, 06:44 PM   #9 (permalink)
Master EcoModder
 
bondo's Avatar
 
Join Date: Jan 2008
Location: Arkansas
Posts: 279
Thanks: 90
Thanked 238 Times in 89 Posts
One more thing Aerohead.

It does make me feel good when you said the architecture of the Aerolid follows correct aerodynamic parameters. In tooling the Aerolid, it was pure sculpture and nothing else. I had no information to go on. I am very fortunate to have arrived at an aerodynamically functional design purely by chance.

When you posted you're now legendary aerodynamic streamlining template, I immediatley copied it and overlayed it upon a picture of my truck. I was very pleased, and relieved, to see the curve of the Aerolid matched the template so closely.

I appreciate all you have done here on ecommoder and without people like you and Darin who understand the numbers and calculations of Engineering, there would be no progress. Sculpture is art, form can be functional. Aerodynamics is a wonderful blend of art and Engineering.

Bondo
  Reply With Quote
Old 02-22-2010, 07:31 PM   #10 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,237

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
Thanks: 3,796
Thanked 6,655 Times in 3,447 Posts
Quote:
Aerodynamics is a wonderful blend of art and Engineering.
Art plus engineering, I agree!

But I don't think it's a fluke that some designers are able to sculpt flow-friendly shapes without the benefit of CFD or training (or template overlays). Aero isn't necessarily intuitive, but some people just seem to get it. The Varna Diablo comes to mind as well.

__________________
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
free OBD2 software with MPG calc whitewiz Instrumentation 11 12-10-2014 10:53 AM
Project: Rebuilding an '01 Honda Insight as a nonhybrid Fabio Hybrids 158 01-12-2013 11:59 AM
SGII first observations! gone-ot Success Stories 10 04-02-2010 01:26 AM
mpguino acted up today, lost mpg during fuel cut wagonman76 OpenGauge / MPGuino FE computer 9 06-17-2009 12:25 PM
performance chips. Do they really increase MPG? regor EcoModding Central 3 07-02-2008 03:08 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com