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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-24-2020, 07:54 PM   #1 (permalink)
Eco Rodder
 
Join Date: Nov 2014
Location: Walnut Creek, CA
Posts: 42
Thanks: 14
Thanked 17 Times in 10 Posts
Learn me some about rear spoilers

I'm now driving my 66 Chevelle eco project and am getting over 30 mpg.
Im working on a front air dam now and will probably add a small splitter to the bottom of it.
is there any kind or a rear spoiler I could add to the rear of the trunk lid to help airflow off the back?
Either a small wickerbill or a flat extension. Which would be better for economy? I don't need downforce.
And how do I calculate the overall height or length and the fore-aft placement along the trunk lid?
Thanks,

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-24-2020, 08:14 PM   #2 (permalink)
Rat Racer
 
Fat Charlie's Avatar
 
Join Date: May 2011
Location: Route 16
Posts: 3,552

Al the Third, year four - '13 Honda Fit Base
Team Honda
90 day: 42.9 mpg (US)
Thanks: 1,411
Thanked 1,549 Times in 985 Posts
Use the aerodynamic template. Make a spoiler that makes your car fit.

__________________

Quote:
Originally Posted by sheepdog44 View Post
Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

  Reply With Quote
The Following User Says Thank You to Fat Charlie For This Useful Post:
aerohead (03-25-2020)
Old 03-24-2020, 10:49 PM   #3 (permalink)
Eco Rodder
 
Join Date: Nov 2014
Location: Walnut Creek, CA
Posts: 42
Thanks: 14
Thanked 17 Times in 10 Posts
Very interesting tool. But will this help me with a spoiler solution? I can see how this would size a kamback but not a spoiler.
Do I add a spoiler up to meet the line? Like a wickerbill? At what angle?
Or do I go back to meet the line? And at what angle? The last of my trunk lid rolls down quite a bit.
  Reply With Quote
The Following User Says Thank You to 67-ls1 For This Useful Post:
aerohead (03-25-2020)
Old 03-24-2020, 10:56 PM   #4 (permalink)
Master EcoModder
 
me and my metro's Avatar
 
Join Date: Jun 2008
Location: Oregon
Posts: 426

Economy Saturn - '02 Saturn L200
Thanks: 172
Thanked 131 Times in 109 Posts
I would try a lid extension that is similar to what the pro stock drag racers’ run. I don’t know if i will help your mileage but it would very cool on your Chevelle.
__________________
02 Saturn L200 5 speed
84 Gmc 6.5 na diesel K30 4x4
  Reply With Quote
The Following User Says Thank You to me and my metro For This Useful Post:
aerohead (03-25-2020)
Old 03-25-2020, 05:58 AM   #5 (permalink)
Rat Racer
 
Fat Charlie's Avatar
 
Join Date: May 2011
Location: Route 16
Posts: 3,552

Al the Third, year four - '13 Honda Fit Base
Team Honda
90 day: 42.9 mpg (US)
Thanks: 1,411
Thanked 1,549 Times in 985 Posts
Build a spoiler to meet the line. Go up if you want a spoiler, go back if you want to build a boattail.
__________________

Quote:
Originally Posted by sheepdog44 View Post
Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

  Reply With Quote
The Following User Says Thank You to Fat Charlie For This Useful Post:
aerohead (03-25-2020)
Old 03-25-2020, 11:23 AM   #6 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 10,856
Thanks: 17,143
Thanked 5,809 Times in 3,501 Posts
rear spoiler

Quote:
Originally Posted by 67-ls1 View Post
Very interesting tool. But will this help me with a spoiler solution? I can see how this would size a kamback but not a spoiler.
Do I add a spoiler up to meet the line? Like a wickerbill? At what angle?
Or do I go back to meet the line? And at what angle? The last of my trunk lid rolls down quite a bit.
CAR and DRIVER experimented with airdams and spoilers on a Ford Pinto,a Dodge Van, and a Datsun 240-Z.
A wrap-around airdam would help keep air from under the Chevelle,cutting drag and front lift (my '67 El Camino was terrifying at an indicated 120-mph!)
A rear spoiler,tilted up at no more than 30-degrees above horizontal,just touching the 'template's' imaginary contour might be a good first approximation.Theoretically,a straight- back foil, ala NHRA/Bonneville,would be lower drag,but it would have to be 'soft' like the rubber-edged Porsche 911 Carrera 'whale-tail' employed, to protect pedestrians.
Rocker panel extensions like on the Trans AM Firebird, even with the bottom of your airdam would help.
Forget the splitter.It will only create drag.
An electric cooling fan if you don't already have one. Keep the fan shroud.
Block all the grille except for the actual perimeter footprint of the radiator.
The headlight recesses could be covered with Plex/Lexan.
MOON covers are a known drag reducer.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 03-25-2020, 12:45 PM   #7 (permalink)
Eco Rodder
 
Join Date: Nov 2014
Location: Walnut Creek, CA
Posts: 42
Thanks: 14
Thanked 17 Times in 10 Posts
Quote:
Originally Posted by aerohead View Post
CAR and DRIVER experimented with airdams and spoilers on a Ford Pinto,a Dodge Van, and a Datsun 240-Z.
A wrap-around airdam would help keep air from under the Chevelle,cutting drag and front lift (my '67 El Camino was terrifying at an indicated 120-mph!)
A rear spoiler,tilted up at no more than 30-degrees above horizontal,just touching the 'template's' imaginary contour might be a good first approximation.Theoretically,a straight- back foil, ala NHRA/Bonneville,would be lower drag,but it would have to be 'soft' like the rubber-edged Porsche 911 Carrera 'whale-tail' employed, to protect pedestrians.
Rocker panel extensions like on the Trans AM Firebird, even with the bottom of your airdam would help.
Forget the splitter.It will only create drag.
An electric cooling fan if you don't already have one. Keep the fan shroud.
Block all the grille except for the actual perimeter footprint of the radiator.
The headlight recesses could be covered with Plex/Lexan.
MOON covers are a known drag reducer.
On further examination, I canít possibly reach the line with a spoiler. It would be like 8Ē tall @ 30 degrees or @ 12Ē+ if straight back.
Would a partial spoiler help at all?

I may add some side skirting but not to the bottom of the front air dam.
I do run an electric fan and the grill opening is already smaller than the face of the radiator. I may reduce this some because the face is designed for a big block and Iím running a 217 cubic inch V6.
Moon covers while efficient are not in the cards. I dont have a way to attach them to my wheels.
  Reply With Quote
The Following User Says Thank You to 67-ls1 For This Useful Post:
aerohead (03-25-2020)
Old 03-25-2020, 02:45 PM   #8 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 10,856
Thanks: 17,143
Thanked 5,809 Times in 3,501 Posts
can't possibly

Quote:
Originally Posted by 67-ls1 View Post
On further examination, I canít possibly reach the line with a spoiler. It would be like 8Ē tall @ 30 degrees or @ 12Ē+ if straight back.
Would a partial spoiler help at all?

I may add some side skirting but not to the bottom of the front air dam.
I do run an electric fan and the grill opening is already smaller than the face of the radiator. I may reduce this some because the face is designed for a big block and Iím running a 217 cubic inch V6.
Moon covers while efficient are not in the cards. I dont have a way to attach them to my wheels.
Run a simple straight line off the back of the roof,down at 23-degrees and see what that looks like.That's the absolute maximum slope the car can tolerate without flow separation of the central downwash core.If you can capture a locked-vortex between the top of the spoiler and top of the roof,the 'sound' flow (as Hucho calls it) will skip over that vortex kinda as if it were a solid structure.You'll pay for all the kinetic energy lost to feed the vortex,but it should kill the rear lift,and with it,some drag.Can't say how much.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 03-25-2020, 04:44 PM   #9 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 15,230
Thanks: 3,852
Thanked 5,078 Times in 4,044 Posts

https://i.pinimg.com/736x/8c/16/c0/8...c63e86979b.jpg

I don't see a problem. Just don't back into pedestrians.

You might consider sail panels that roll vortexes down onto the deck lid to constrain the size of the wake.
__________________
.
Gold is the money of kings
Silver is the money of gentlemen
Barter is the money of peasants
óbut debt is the money of slaves
Norm Franz

_________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
me and my metro (03-25-2020)
Old 03-26-2020, 10:45 AM   #10 (permalink)
EcoModding Lurker
 
Join Date: Dec 2016
Location: Florida
Posts: 13
Thanks: 6
Thanked 9 Times in 8 Posts
IMO, a rear spoiler is supposed to "spoil" air flow, and therefore increasing the local air pressure upon a surface up stream, to intentionally increase DF. Increased drag is thought to be an acceptable trade off in most cases.

A flat added extension (trunk?) should, again IMO, maybe better be called a "smoother (or divider?)", which might reduce drag. If a "smoother", just by forming a hard boundary between a higher pressure area and a lower pressure area in space, will also increase potential DF, with little drag increase, if any.

Doesn't seem to me that a typical rear spoiler often reduces drag, leading to better mpg.


Last edited by j-c-c; 03-26-2020 at 10:58 AM..
  Reply With Quote
The Following User Says Thank You to j-c-c For This Useful Post:
aerohead (Today)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com