Rear Wind Deflector Mod !

[FordFasteRR]

I was thinking... to help reduce the drag on the car in the 1/4 mile.. I could add a sheet-metal wind deflector under the car that prevents air from getting trapped in the rear bumper as the car moves forward..

I don't have any images of this mod at the moment.. however I will be doing this mod on thrusday long with my light weight battery install.

I'll post plenty of pics and a DIY on it when i'm done.


Here is a picture of ronniesans XD, I dont think mine will be exactly the same as his due to the dual exhaust he has and such... but this should give you all a general idea of what needs to be done for this mod to work....

http://www.nitrousworld.com/pictures/Exhaust.JPG


Well, lets hear the comments on this !!! :phone:

[RonnieSan]

Maybe you can just fill the rear bumper with that foam installation stuff that expands when you spray it. Might be lighter than a piece of sheet metal, but I wouldn't really know.

[FordFasteRR]

well i would use paper thing sheet metal.. its ultra light for just a small piece in the back of the car...

:)

but that foam stuff is a good idea ! I just have to figure out a way to keep it from drippin out of the bumper after i spray it in there ! LOL

[Blackdiamond]

Well a friend of mine dad drilled 2 1/2 inch holes along the bottom of the rear bumper of his vette (spaced them an inch apart.. and at the lowest part of the bumper).... and made sure nothing was blocking them... cut 2 seconds off his 1/4 times

[FordFasteRR]

Well a friend of mine dad drilled 2 1/2 inch holes along the bottom of the rear bumper of his vette (spaced them an inch apart.. and at the lowest part of the bumper).... and made sure nothing was blocking them... cut 2 seconds off his 1/4 times



2 seconds...

2 whole seconds....................... !! ?

[yevRPS]

did he fit a small jet nozzle in each of the holes? 2 seconds sounds like waaaaaaaay too much and i don't even know all that much about drag racing.

[FordFasteRR]

a rear bumper does not slow a vette down by 2 seconds..

lol

[Blackdiamond]

Whoops my bad 2/10ths of a second... typing to quick again.. :)

[FordFasteRR]

thats more like it ! LOL :)

[GTSTISL]

Still, 2 tenths of a seocnd of quarter mile times, especially in a vette, is great! Plus its free, besides the fast that you have a ton og holes in the bumper!

[Keyan]

To test this mod to make sure it works before commiting to it and spending money, couldn't you just run a 1/4 mile with a rear bumper, then without...which would show you what the MAXIMUM GAINED from any mod to the rear bumper would be...and then you could mod the bumper and work from there.

[faraco3]

Make sure you use sheets of aluminum rather than steel

[FordFasteRR]

ok i'll try to find some very thin aluminum sheets... lol

[GodisintheTV]

i have friends that had 3 one inch round holes in thier rear bumper for the wind to pass through, they said it worked

[FordFasteRR]

i have friends that had 3 one inch round holes in thier rear bumper for the wind to pass through, they said it worked


thats great, but how stupid do would an elantra look with 3 tennis-ball size holes drilled out of the rear bumper ?

Also, there is a foam insert between the bumper and the inner-fender and those holes basically will not work on our cars unless you remove the foam insert ... I dont care to start taking panels off of my car + i dont plan to drill any holes in my bumper ! LOL

:)

That is why the deflector is my ONLY option in this area. :eek:

[tharptroy]

I think I may have mentioned this to you a long time ago.

I say get after it. I could see picking up 2 tenths.

[azwildfire]

wind resistance is an exponetial function. that means it goes up REALLY fast at higher speeds

in a vet with a 120 mph 1/4 mile catch time, they would have MUCH larger benifits then a hyundai with a 90 mph 1/4 mile catch time

ever notice how much more crappy your gas milage is above 80? it isnt that your engine runs less efficient at higher rpms, it is because it takes a LOT more energy to over come the wind resistance from 70-80 compared to the wind resistance of 60-70

if you want to see the math behind it... here are some goof physics links
http://www.physics.gmu.edu/~amin/phys251/Topics/NumAnalysis/Odes/projectileMotion.html

http://www.newton.dep.anl.gov/askasci/phy00/phy00271.htm

If you want the formula for air resistance, sometimes called aerodynamic
drag, a formula that works well is (drag force)=-b*(speed)^2. Aerodynamic
drag is proportional to the square of the object's speed. The "b" is a
constant determined by experiment, based on all things mentioned above.
There is no theoretical value for "b".


notice the squared power? that is what makes wind resistance called an exponetial function!

the graph of exponetial functions look like this http://mathforum.org/alejandre/ss.exp.step7.gif

no what other related objects in our cars have this graph shape? the voltage of our MAFS :P *just going back to the point about maxing them out hehe*

[SuperGLS]

Seems like it would work to me. Good luck finding a good lightweight material to use. I wouldn't suggest the foam insulation spray stuff, it actually isn't that light. It's used in a lot of appliance applications so I can tell you first hand it's heavier than it appears.

Oh, and that first Physics link is a a gmu.edu link, that's my school, yay Patriots (eww, someone please make fun of me without going off topic).

[CTele02]

Wasn't there a commercial out a while ago about aerodynamics not just above the car but under it? I think it was for a honda accord or some big sedan, maybe you could look into the "aerodynamics" of those cars if you find one that was factory made to reduce air resistance..

[azwildfire]

i by no means ment to imply this would not help with drag and thus improve fuel economy and 1/4 mile times, i just wanted to try to keep people in reality that they would not likely see the same great results as a vet does

[FordFasteRR]

agreed.

[jimnran]

Not only would it look bad but the holes would cause a horrible "whistle" sound at highway speeds I would think. I might be off my meds here, but having my window cracked open on the freeway drives me nuts! Just my 2 cents.

Jim

[XWRed5W3]

Yeah, I remember that commercial ctele - It was pretty much a flat sheet of aluminum, but there were dimples in it like golf balls to help with the aerodynamics. Maybe you could try something similar Ford?