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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 02-16-2010, 11:41 PM   #1 (permalink)
Master EcoModder
 
AeroModder's Avatar
 
Join Date: Jan 2010
Location: Oregon
Posts: 471

Tank - '96 Ford Aspire 4 door
Team Ford
90 day: 46.75 mpg (US)
Thanks: 15
Thanked 65 Times in 48 Posts
Air Dam vs. Front Undertray- One negates the other?

I found out that the extra scraps of coroplast I had were the perfect measurements for a front air dam. I already have a front undertray in place, though.

What I'm wondering is, will an air dam negate the effects of a front undertray? Would I be better off removing the undertray when I install the air dam?

__________________
In Reason we Trust
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 02-16-2010, 11:45 PM   #2 (permalink)
ecomonkey
 
Join Date: Dec 2009
Location: middleburg fl
Posts: 240

silver clown - '02 toyota echo 2 door base
90 day: 47.16 mpg (US)

white ghost - '05 prius base
90 day: 47.53 mpg (US)

white pearl - '12 toyota prius base
90 day: 46.81 mpg (US)
Thanks: 33
Thanked 30 Times in 21 Posts
a smoother undertray will always help, some air will always get under ,and it might allow you to use a smaller air dam which is good because a dam increases frontal area,,, just my 3 cents.
__________________
  Reply With Quote
Old 02-17-2010, 12:15 PM   #3 (permalink)
Master EcoModder
 
wagonman76's Avatar
 
Join Date: Jun 2008
Location: Northwest Lower Michigan
Posts: 1,006

Red Car - '89 Chevrolet Celebrity CL 4 door
Team Chevy
90 day: 36.47 mpg (US)

Winter Wagon - '89 Pontiac 6000 LE Wagon
90 day: 28.26 mpg (US)
Thanks: 8
Thanked 17 Times in 16 Posts
It probably depends a lot on what the rest of the underside of the car looks like. Once I removed my airdam and installed a partial front bellypan, and my mpg went back down to where it was before the airdam, which was about a 2 mpg difference. So the partial bellypan did nothing. In my case it is better to just use the airdam to keep the air out from under the car to start with.
__________________

Winter daily driver, parked most days right now


Summer daily driver
  Reply With Quote
Old 02-17-2010, 01:59 PM   #4 (permalink)
EcoModding Lurker
 
Join Date: Nov 2008
Location: Portland, OR
Posts: 53

Daq Civic - '92 Honda Civic DX sedan
90 day: 42.54 mpg (US)

The Hardbody - '91 Nissan D21 (pickup)

The Hardbody - '91 Nissan D21 (pickup)
Thanks: 1
Thanked 7 Times in 5 Posts
I've been wondering about this on my car too. I've had a front undertray for awhile, which is now full length, but it's at a rather steep angle due to the high front bumper. I'm guessing this is stuffing too much air underneath the car (not more than stock, but still a lot), adding drag despite the smooth surface.

I am now toying with the front dam idea, but how would I combine it with a front undertray, or should I even bother? Just adding a dam would create quite a vacuum area, meaning the air would unattached and turbulent by the time it makes contact with the rest of the undertray. I the best solution of course would be to make a front undertray that is flush with the dam and flat from that point back. But then I'd be grinding it all the time and probably rip it off.
  Reply With Quote
Old 02-17-2010, 02:36 PM   #5 (permalink)
Master EcoModder
 
AeroModder's Avatar
 
Join Date: Jan 2010
Location: Oregon
Posts: 471

Tank - '96 Ford Aspire 4 door
Team Ford
90 day: 46.75 mpg (US)
Thanks: 15
Thanked 65 Times in 48 Posts
Thanks for the advice!

I currently have 3 other panels underneath the car, placed around the exhaust and smoothing out the underside (I have a thread on that in the Ecomodding Central forum: http://ecomodder.com/forum/showthrea...ign-12096.html )

I'll see about lowering the front of my undertray and get it closer to horizontal. I'll need to pick up some longer screws, though.
__________________
In Reason we Trust
  Reply With Quote
Old 02-17-2010, 03:41 PM   #6 (permalink)
EcoModding Lurker
 
Join Date: Nov 2008
Location: Portland, OR
Posts: 53

Daq Civic - '92 Honda Civic DX sedan
90 day: 42.54 mpg (US)

The Hardbody - '91 Nissan D21 (pickup)

The Hardbody - '91 Nissan D21 (pickup)
Thanks: 1
Thanked 7 Times in 5 Posts
Thanks, and after looking at your other thread, your undertray looks great, but I would significantly lower the angle of the rear diffuser. In fact, you don't want a "diffuser" at all. Diffusers create a greater low-pressure area by "diffusing" a given amount of air molecules over a greater volume of space. What you want is a smooth surface that reduces wake profile while keeping attached flow, and 25 degrees is too much to keep attached flow on top of the car, in open air, let alone underneath, where the air is trapped between the ground and underbody. You can search the forum for lengthy discussions on what is optimal, but I would stay around 10 degrees.
  Reply With Quote
Old 02-17-2010, 06:37 PM   #7 (permalink)
Master EcoModder
 
tasdrouille's Avatar
 
Join Date: Jan 2008
Location: Mirabel, QC
Posts: 1,672

The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

Got Soul? - '11 Kia Soul 2U
Thanks: 35
Thanked 85 Times in 56 Posts
I believe they both compliment each other when designed properly. The undertray deals with the floor while the airdam should be designed to deal with the wheels.
__________________



www.HyperKilometreur.com - Quand chaque goutte compte...
  Reply With Quote
The Following User Says Thank You to tasdrouille For This Useful Post:
moonmonkey (02-17-2010)
Old 02-18-2010, 03:10 PM   #8 (permalink)
Master EcoModder
 
AeroModder's Avatar
 
Join Date: Jan 2010
Location: Oregon
Posts: 471

Tank - '96 Ford Aspire 4 door
Team Ford
90 day: 46.75 mpg (US)
Thanks: 15
Thanked 65 Times in 48 Posts
I've got an idea- I'll leave a lip of the air dam over the sides of the undertray so the flow will detach before it goes toward the tires and suspension, but keep the middle section flush with the air dam to have some attached airflow on the undertray. Similar to the air dams on cars that sit lower on the corners and raise up in the middle, but reversed in a way.

Photos to come.
__________________
In Reason we Trust
  Reply With Quote
Old 02-19-2010, 04:36 PM   #9 (permalink)
Master EcoModder
 
AeroModder's Avatar
 
Join Date: Jan 2010
Location: Oregon
Posts: 471

Tank - '96 Ford Aspire 4 door
Team Ford
90 day: 46.75 mpg (US)
Thanks: 15
Thanked 65 Times in 48 Posts
Photos:

Here's showing what I meant, having the undertray curved and the air dam flat:
(Looking at the right front corner from underneath the driver's door)



Corner view:



Front view:




The canards were there to reduce the front-end lift that the undertray seemed to have been causing, and are mounted at 25 degrees. After adding the air dam, I noticed the steering effort at speed was increased, which is a clear indicator of reduced lift/increased downforce. I'll most likely pull those off, since it doesn't seem like I need them anymore. (My goal for the aero is reduced drag with zero lift).

I don't have any mileage numbers yet, but I will once my tank is gone.

My fiancee's cell phone seemed to have raped the size of the first picure, so I'll try to take a better one today.
__________________
In Reason we Trust
  Reply With Quote
Old 02-19-2010, 08:20 PM   #10 (permalink)
EcoModding Lurker
 
Join Date: Feb 2010
Location: Fargo
Posts: 16
Thanks: 0
Thanked 0 Times in 0 Posts
For the undertray, I first made a nice pattern by sticking few pieces together (some foam-core board) then cut according to pattern. Then drilling holes through it and the underlying bracing or brackets after. Finally, securing it with nylon push-rivets.

  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Comparing Warm Air Intakes (WAI) & Cold Air Intakes (CAI) toomuch EcoModding Central 23 05-26-2019 05:41 AM
2007 Focus Front Air Dam garys_1k Aerodynamics 23 12-28-2011 02:22 PM
New front air dam puddleglum Aerodynamics 17 02-10-2010 12:09 AM
Civic grill block, front undertray, tire deflectors daqcivic Aerodynamics 24 05-13-2009 03:52 AM
Moving air intake into the engine compartment? pasadena_commut Aerodynamics 5 07-25-2008 03:24 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