YEs ive searched. i have found threads where the question has been asked but never really answered.
what kind of gaines would one see with diffusers used for drag racing? lets say one runs 10.5000@140.00mph with stock bumber.. what would one expect to have ran that same pass with diffusers?

 

I was wondering the same thing today.

Adriano

 

i hated the way the holes in the rear bumper looked so i didnt do it.....once i got running around 145 or so, the wind actually ripped the bumper off the car. i put holes in the new bumper, its been fine since then, but the car didnt go any faster from it lol

 

Im sure it has some positive effects when going down the track. I personally much rather take the entire rear bumper off than cut holes or a diffuser. Thats just me though.

 

if someone is welling to bring my other bumper to Atco I would be will to see if it make any differance on a 12s car.

pic of bumper with holes, yes I know they are big

 

your car shouldnt run any faster from this mod it should however help keep the car more stable which is the purpose for it. kinda like a front diffuser or splitter

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony413 &raquo;</TD></TR><TR><TD CLASS="quote">your car shouldnt run any faster from this mod it should however help keep the car more stable which is the purpose for it. kinda like a front diffuser or splitter </TD></TR></TABLE> Take note from any car ( exotics, supercars) They may not have holes but are designed with there version of "holes" in the rear.

 

i just got one of the 92 vx hatch back they come stock on them.

 

 

i know this works first hand.

on my old 4dr i had the stock bumper with a type r style rear lip on it, it seemed to hang low and prolly trap air in it...

so i took another rear bumper that i had and cut the bottom/middle out of it like people with srt4's do...

took it too the track ran one run, came back swapped bumpers and ran again...i went 3 tenths quicker and 4mph faster....this is on a car that went 11.7-11.9 consistatly @ 123 mph with the stock bumper lip combo, and then went 11.50 and then 11.43 @ 127 with the cut bumper being the only mod....worked great for me...

 

good info and facts to back it up

 

pics?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IceySC &raquo;</TD></TR><TR><TD CLASS="quote">i just got one of the 92 vx hatch back they come stock on them.</TD></TR></TABLE>

thats not the same thing, were talking about the diffusing plates with the holes for the back of the bumper. The vx just has plastic stuff to close off that area behind the bumper.

 

Take a tray from any fast food restaurant and have a friend drive you around on a freeway. Take the tray and hold it out of the window as if it were to deflect the incoming force of air.

Now, go back home and cut about 16 1-2 inch holes in the tray and go back out on the freeway and repeat the process. I assure you, there will be a lot less resistance the 2nd time around.

Your bumper hangs below the under side of the car acting as a small parachute at high speeds, the diffuser allows air to pass through the bumper rather than acting as a "deflection" piece, or, "air pocket".

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TrackSpeedRacing &raquo;</TD></TR><TR><TD CLASS="quote">Im sure it has some positive effects when going down the track. I personally much rather take the entire rear bumper off than cut holes or a diffuser. Thats just me though. </TD></TR></TABLE>

Ive tried this at the track and I can tell you that taking the rear bumper off slows the car down on a 92-95 hatch. I think it effects the airflow down the sides of the car.

Holes in the rear bumper got me a few MPH and a tenth or two on 103mph car.

We have a cheap wind tunnel about 45 minutes away from me. I need about $690 and a couple of hours and I could tell you how it all works.

http://www.a2wt.com/info.html

 

I didnt ever take any pics with teh rear bumper on (the cut up one) but here is some world famous paint to get my point across lol
stock bumper with lip


where i cut the stock rear bumper (extra one with no lip) i cut it up until it was flush with the gas tank and in about 6 inches from each side...


hope that makes sense

 

i never really liked just putting holes in the rear bumper, this is the way i did mine and seem to work pretty well

 

Wanna thank any of your sponsors since you posted your car up there?

 

what does that mean grinderguy? care to explain

 

i keep hearing ppl say the vx bumber comes with a diffuser, can someone post a pic?

also in another archive thread one person said ..

quote//There is a huge difference between cutting holes in your rear bumper cover and actually installing a functional diffuser. Diffusers for a street application are totally useless. quote//

i can not see why there would be any difference, i mean a hole is a hole, right?
im ready to go start cutting unless someone agrees that there is a reason golden ealge charges $100 for there diffuser.

 

any suggestions on what tool to use to cut out circles?

 

i wish i had sponsers to pay for my car

 

hole saw....



the 4 door....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hardt &raquo;</TD></TR><TR><TD CLASS="quote">Take a tray from any fast food restaurant and have a friend drive you around on a freeway. Take the tray and hold it out of the window as if it were to deflect the incoming force of air.

Now, go back home and cut about 16 1-2 inch holes in the tray and go back out on the freeway and repeat the process. I assure you, there will be a lot less resistance the 2nd time around.

Your bumper hangs below the under side of the car acting as a small parachute at high speeds, the diffuser allows air to pass through the bumper rather than acting as a "deflection" piece, or, "air pocket".</TD></TR></TABLE>

Or you could take two trays and put them under your back tires and yank up on the e-brake and have fun in a parking lot

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ludman95 &raquo;</TD></TR><TR><TD CLASS="quote">

Or you could take two trays and put them under your back tires and yank up on the e-brake and have fun in a parking lot </TD></TR></TABLE>

Nah, damn rookies got to do it with the Gas main cover on the sidewalks or so I have heard