has anyone seen a major increase in mph with a diffuser.

 

a buddy of mine gained 2 mph on his traps.. went from 119 to 121..

 

ive seen people gain from 1-3mph through the traps as well. I say test it with bumper on, and with bumper off. and make your decision. good luck.

 

...You mean do a back 2 back test with a diffuser installed and with a stock bumper not cut. Im sure it will be minimal, but every little bit counts.

 

the reason I said do the "test" with bumper off is the make a more clear comparison of how much the bumper acts as a "mini" parachute. There are ways to get around this problem with out even removing the bumper or putting holes.

 

my friend picked up several mph but i dont like the look of holes so i just bought a certifit bumper for the track its only around $40 and i can hack it up all i want

 

Holes in the bumper does not exactly qualify as a 'diffuser'. The holes don't take into effect the smoothing/reducing of the air pressures nearly as much as a diffuser will.

 

I did a back to back with two different bumpers and picked up nothing for mph or e.t.

 

I just took a hole saw to my back bumper on my hatch... well see if I can run 10s this year

 

i did back to back testing within an hour of each other. my car was very consistant as well.

went from 11.7x's @ 124-125 to 11.51, then 11.43 both at 127.

i didnt cut holes in my bumper, but i did cut off the lower part of the bumper, right up to the bumper support.

there is many threads on this already...i must have posted pics and my experiences in about 9 different threads lol

 

i think people are gettin diffusers confused with holes in the bumpers

 

..Please explain

 

Diffuser......





not a diffuser......

 

yep, although the product in the last pic is definitely marketed and sold as a "diffuser"

I'd say if you're that worried about drag being caused by the air getting trapped in the rear bumper, just take the damn thing off.

 

I was waiting for the brawn car to pop up

 

We took a car to the track with holes in the rear bumper and ran it, duct taped over the holes and ran, then we removed the rear bumper and ran it again. It was fastest with the bumper on with holes in it.

lol :highfive:

 

while these examples are more on the high-end, it has really helped with stability at speeds in excess of 135mph. more notable is the stability when braking as well.

 

....All the pics above IMO, all act as air diffusers. They are just different ways to manipulate the air at high speeds.
Like someone stated already, the pic. of the EK with the GE rear bumper diffuser is marketed and sold as just that. Right from the GE website:

BUMPER DIFFUSER
-Precision CNC machined from 6061T6 billet aluminum
-Allows air to travel through the rear bumper reducing wind drag

 

You are not allowed to do underbody work like that on a Honda. It improves the low buck, ricer image that we have on the scene. Please market that as a chevy immediately.

Holes in the bumper are ugly.....even worse is the hacked up rear bumper that looks so extremely stupid that people can't help but laugh. Look at T1s bumper flaps before cutting thru holes in the bumper.

 

^^^^^^^^^^

..i agree, cutting the holes in the bumper doesn't look good.
and i for sure didn't want the GE kit.

...So i took advantage of the sheetmetal shop @ work

 

thank all u guys for for feedback and comments. im having a problem with a car im tuning and i think its the back bumper.

 

lmao

 

let me be more clear for the d##ks. what i meant was the car is making 250++ and only running 11.8 ish is the 1/4mile and it seems like there is some sort of wind resistance because its runnin fast through the 330ft and 1/8 mile but the quarter is slower. i think its due to wind resistance because the power and weight are not the problem and the driver is very consistant. have i cleared it up for the people that didnt understand what i menat

 

..any more info on the car? setup, chassis, weight?

..doesn't sound to bad if its a mild all motor B

 

just messin with u but u got 2 admit does sound funny..

i did a test at the track with drilling 6 holes on each side of my bumper and the only diff was about 2-4mph higher & at best .01-.07 faster ET. my car is also a very consistent car running 10.30s all day at 145.
but u wouldn't feel the diff . nor is it effective unless your trapping 140+ to me