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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 09-04-2012, 02:49 PM   #11 (permalink)
eco-scrapper
 
Join Date: Sep 2009
Location: New Kensington PA
Posts: 69

Big Blue - '94 Ford F-150 shortbed
90 day: 15.71 mpg (US)

Mexico Nuevo - '84 Honda V45 Sabre
90 day: 36.67 mpg (US)
Thanks: 4
Thanked 10 Times in 7 Posts
I doubt that putting the block behind the grillwork would make a big aero difference, for the following:

The front grill on an auto is at--or very near to--the stagnation point on the nose. Thus, the flow velocity near the vehicle is zero, or very close to that.

What happens is that the air upstream of the car "senses" the blockage...and the vast majority of the air flows AROUND the obstruction. This is true of all sub-mach flow. (Sometime look at the "grease streaks" you see on aircraft rivets...the airflow on the fuselage just ahead of the wing has a pronounced upward flow component, as the air tries to fill the low-pressure are on the top of the wing.)

So, keep it under 720 MPH, and it makes little difference. Above that, you want knife-edge leading edges anyways.

__________________
  Reply With Quote
The Following User Says Thank You to meanjoe75fan For This Useful Post:
ChazInMT (09-18-2012)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 09-05-2012, 08:57 AM   #12 (permalink)
Hypermiler
 
PaleMelanesian's Avatar
 
Join Date: Dec 2007
Location: Texas
Posts: 2,321

PaleCivic (retired) - '96 Honda Civic DX Sedan
90 day: 69.2 mpg (US)

PaleFit - '09 Honda Fit Sport
Team Honda
Wagons
90 day: 44.06 mpg (US)
Thanks: 611
Thanked 433 Times in 283 Posts
I'm not sure your cause and effect follow each other.

Correct that the grille is near the stagnation point. (more on some cars than others) A rear block will cause air to "pile up" in the blocked cavities. The rest of the air will flow mostly smoothly over those pockets of air. A rear block should work nearly as well as a smooth outer block.

You do have to get past that pesky problem of the air pushing it in and then leaking around the block. A front block doesn't have the problem.
__________________



11-mile commute: 100 mpg - - - Tank: 90.2 mpg / 1191 miles
  Reply With Quote
Old 09-17-2012, 07:10 PM   #13 (permalink)
EcoModding Lurker
 
royanddoreen's Avatar
 
Join Date: Jun 2010
Location: glovertown nl canada
Posts: 91

z - '03 nissan 350z touring
90 day: 36.21 mpg (US)

Diniro - '18 Kia Niro Ex
90 day: 47.99 mpg (US)
Thanks: 37
Thanked 6 Times in 4 Posts
Quote:
Originally Posted by darcane View Post
I had one on my truck inside the grill. The way I had it mounted, it would flex and allow air to flow past it and wasn't very effective. I noticed an improvement by moving to the front of my grill.

I think if you mount behind the grill, you need to make sure it will still prevent air from flowing around the block once the vehicle is moving.

Mounting in front of the grill makes this easy, since air pressure will keep the block in place.
Cool just fabricate it so you get just enough air,, thanks
  Reply With Quote
Old 09-17-2012, 10:42 PM   #14 (permalink)
Master EcoModder
 
mcrews's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 3,523

The Q Sold - '02 Infiniti Q45 Sport
90 day: 23.08 mpg (US)

blackie - '14 nissan altima sv
Thanks: 2,203
Thanked 663 Times in 478 Posts
see the grill block thread in my signature on a plexiglass front block
__________________
MetroMPG: "Get the MPG gauge - it turns driving into a fuel & money saving game."

ECO MODS PERFORMED:
First: ScangaugeII
http://ecomodder.com/forum/showthrea...eii-23306.html

Second: Grille Block
http://ecomodder.com/forum/showthrea...e-10912-2.html

Third: Full underbelly pan
http://ecomodder.com/forum/showthrea...q45-11402.html

Fourth: rear skirts and 30.4mpg on trip!
http://ecomodder.com/forum/showthrea...tml#post247938
  Reply With Quote
Old 09-18-2012, 01:29 PM   #15 (permalink)
Master EcoModder
 
Phantom's Avatar
 
Join Date: Jan 2010
Location: Independence, KY
Posts: 603

Blue Meanie - '02 Volkswagon Golf TDI
TEAM VW AUDI Group
90 day: 48.52 mpg (US)

Wife's car - '05 WV Passat TDI

Rudy - '94 Chevy C2500
Thanks: 89
Thanked 47 Times in 44 Posts
It depends on the vehicle if air can go around a behind the grill block. On my grandprix I used plexy for picture fraims and cut it to the grill insert installed and the air presses it tighter. The same is true for my Golf as the grill sits against a support and the air tightens the seal.
__________________
I move at the speed of awesome.


"It's not rocket surgery!" -MetroMPG
  Reply With Quote
Old 09-24-2012, 08:52 PM   #16 (permalink)
EcoModding Apprentice
 
Join Date: Feb 2012
Location: Burlington, ON
Posts: 158

minispeed-Insight - '00 Honda Insight
90 day: 82.15 mpg (US)

MDX - '01 Acura MDX Touring
90 day: 22.29 mpg (US)

the wife's car - '13 Toyota Prius Plus
90 day: 45.99 mpg (US)

leaf-one - '15 Nissan Leaf SV
Thanks: 4
Thanked 36 Times in 26 Posts
I have an inner block behind my grill which is only about 1/2in deep but I took the grill off used coroplast, black just like the grill. Then used Gorilla duct tape on the edges and it seals perfectly.

Now it's getting time for the lower block soon!

__________________






  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com