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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-04-2010, 11:17 PM   #21 (permalink)
Left Lane Ecodriver
 
RobertSmalls's Avatar
 
Join Date: Aug 2008
Location: Buffalo, NY, USA
Posts: 2,257

Prius C - '12 Toyota Prius C
Thanks: 79
Thanked 284 Times in 197 Posts
It looks like you were only able to reduce your trailing wake area by about 20-25%, so a 10% reduction in drag (for a slightly smaller % reduction in highway fuel economy) would not be surprising.

In an ideal world, you'd taper the sides inward for a larger reduction in rear area. In reality, that's difficult to execute with plywood, and it's nice to have the bedrails under your aero cap. In a very ideal world, you'd taper the sides of the bed inwards, too.

You can use the same template as you did for the side view, but line up the ground plane of the template with the center line of the truck. If your shape curves inward from both sides and from the top, you can get away with sharper shapes than the template suggests. How much sharper? I do not believe anyone here can tell you (except to recommend you imitate the EV1 and Honda IMAS), so you'd be flirting with flow seperation.

But back to reality. You have a classy looking cap, and I like the overhang. If you want further drag reduction, you'll need to find room for more reduction in trailing area. You've already plucked the low-hanging fruit in that department.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-05-2010, 09:58 AM   #22 (permalink)
Quest for a 400 mile tank
 
mjboks's Avatar
 
Join Date: Jul 2009
Location: West Michigan
Posts: 45

Adventure Truck - '07 Toyota Tacoma Double cab V6 TRD 4wd offroad
90 day: 19.26 mpg (US)

Commuter Bicycle - '94 Slingshot mountain bike
Thanks: 37
Thanked 6 Times in 6 Posts
template overlay

I took your image from the other thread and overlaid the template. Not sure if it's the angle of the camera or not but it looks like your cap is a bit on the conservative side... better than too steep and getting separation.

Here's the image with a couple simple lines drawn in if you did a tailgate extension.
Attached Thumbnails
Click image for larger version

Name:	ccrider cap.jpg
Views:	149
Size:	64.0 KB
ID:	5705  
  Reply With Quote
Old 03-05-2010, 01:04 PM   #23 (permalink)
Recreation Engineer
 
KamperBob's Avatar
 
Join Date: Dec 2009
Location: Somewhere USA
Posts: 521

Black Stallion - '02 Toyota Tundra 4WD xCab

Half Pint - '06 Yamaha XT225
Thanks: 311
Thanked 136 Times in 101 Posts
Is the back open or closed?

Cheers
KB
  Reply With Quote
Old 03-05-2010, 01:37 PM   #24 (permalink)
EcoModding Lurker
 
Join Date: Nov 2009
Location: poughquag new york USA
Posts: 69

old red taco - '02 toyota tacoma regular cab
90 day: 29.49 mpg (US)
Thanks: 1
Thanked 27 Times in 15 Posts
Quote:
Originally Posted by mjboks View Post
I took your image from the other thread and overlaid the template. Not sure if it's the angle of the camera or not but it looks like your cap is a bit on the conservative side... better than too steep and getting separation.

Here's the image with a couple simple lines drawn in if you did a tailgate extension.
the truck is slightly lower in the front in the picture if you look at the black bed liner under the cap compared to the template bottom. if the truck is perfectly flat the template matches up pretty close.

kamperbob the tailgate was closed during the tests. not sure if that is what you are asking. but the back of the cap has a piece of plywood on it.

i think i should do what metrompg said and move on to the under side of the truck. i think that my results showed that the big mpg loses as speed increased tells me that trucks have very bad aerodynamics and that if i clean up the bottom i should see less loses as speed increases.

since the test i have been more aware of wind conditions and yesterday i was driving from Tampa to Melbourne and i had a 10-15 mph tail wind and i was averaging over 30 mpg on the scangauge at 65 mph. which makes sense because i was getting around 30 mpg at 55mph on my tests
  Reply With Quote
Old 03-05-2010, 02:02 PM   #25 (permalink)
Recreation Engineer
 
KamperBob's Avatar
 
Join Date: Dec 2009
Location: Somewhere USA
Posts: 521

Black Stallion - '02 Toyota Tundra 4WD xCab

Half Pint - '06 Yamaha XT225
Thanks: 311
Thanked 136 Times in 101 Posts
Quote:
Originally Posted by ccrider View Post
kamperbob the tailgate was closed during the tests. not sure if that is what you are asking. but the back of the cap has a piece of plywood on it.
Good. I meant the cap not the tailgate. (I was wondering about possible reduced pressure *inside* the cap (vacuum effect) acting on large vertical surfaces, but if the cap was closed that should not be a factor.)

Cheers
KB
  Reply With Quote
Old 03-05-2010, 02:09 PM   #26 (permalink)
Quest for a 400 mile tank
 
mjboks's Avatar
 
Join Date: Jul 2009
Location: West Michigan
Posts: 45

Adventure Truck - '07 Toyota Tacoma Double cab V6 TRD 4wd offroad
90 day: 19.26 mpg (US)

Commuter Bicycle - '94 Slingshot mountain bike
Thanks: 37
Thanked 6 Times in 6 Posts
Quote:
Originally Posted by ccrider View Post
the truck is slightly lower in the front in the picture if you look at the black bed liner under the cap compared to the template bottom. if the truck is perfectly flat the template matches up pretty close.
Thought that might be the case. The bed rail shows a bit of a downward angle in the image.
  Reply With Quote
Old 03-11-2010, 03:55 PM   #27 (permalink)
EcoModding Lurker
 
Join Date: Nov 2009
Location: poughquag new york USA
Posts: 69

old red taco - '02 toyota tacoma regular cab
90 day: 29.49 mpg (US)
Thanks: 1
Thanked 27 Times in 15 Posts
i just filled up my gas tank after doing my ABA test and the scangauge was not accurate on the fuel consumption on my truck. the scangauge though i used 13.6 gallons and i only used 12.96 gallons. so the scangauge was figuring the mpg 4.94% low (i just got it back from repair) i also thought the mpg's were a little low for my truck. so the actual mpg's for the test would be

A 28.045

B 27.048

A 28.333

gain 1.142

gain percentages still stay the same as metrompg stated
  Reply With Quote
Old 03-12-2010, 09:56 AM   #28 (permalink)
Aero Wannabe
 
COcyclist's Avatar
 
Join Date: Dec 2007
Location: NW Colo
Posts: 697

TDi - '04 VW Golf
TEAM VW AUDI Group
90 day: 55.54 mpg (US)
Thanks: 627
Thanked 196 Times in 154 Posts
On another thread Aerohead suggested putting ballast in the car to simulate driver and passenger weight before determining the correct angle for a boattail from the template. As I recall, you said you need to haul things in your truck bed from time to time. I had this thought that it may be better to be conservative in your angles (as I think you are) than to get them just right and have it too steep as soon as you put a load in the bed of the truck.

__________________
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun
https://ecomodder.com/forum/showthre...tml#post621801


Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to properly test modifications (AKA: don't believe every MPG claim you read) MetroMPG EcoModding Central 119 11-20-2020 06:28 AM
Aerocap for a Tacoma Pickup? mjboks Aerodynamics 88 03-24-2015 05:04 PM
issue with the aba test TheDon EcoModding Central 2 06-17-2008 06:18 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