That website is too simplistic and downright inaccurate: more downforce =faster? not true.

Here is a better website even though it's for model RC which sees equivalently to 300 mph when scaled up.

http://users.pandora.be/elvo/c7/

 

ummmm isn't that page what I just said? I was going to quote that exact page strangely enough just when you posted:

"The diffuser, or floor, is designed to ensure the smoothest exit for the air that is flowing under the car. Designers come up with a huge variety of complicated shapes because the quicker the air exits, the more downforce the car generates, and the faster it will be."

Read "smoothest exit for the air".

I shouldn't have said that it doesn't cause downforce. I didn't consider the diffuser to cause downforce before because overall it holds the car to the road through suction and didn't think that was the same thing? Some websites refer to these as the same so I guess I am wrong and will admit to it. Either way I think we're all just trying to be better informed - at least I am. So no need for arguing I appreciate the info.

 

You are correct in that the website is simplistic.

However, it is true that more downforce=faster whether it be road racing or drag racing.

It is drag which occurs with downforce which causes the loss of speed. Downforce, per se, should not result in loss of speed.

And, a diffuser minimizes drag while increasing downforce.

 

so now you're not arguing whether or not the diffuser works, you're arguing about how effective it is? This thread is getting out of hand.

All in all I would say that of course the diffuser works, however it is most likely that RE-A designed their diffusers to work in conjunction with their front, sides, and wing as well... It is possible that adding JUST the diffuser to the rear of the car will cause a bit more lift on the front, but I believe that if someone also has an aftermarket front bumper, especially one from RE-A, then the increased air flow through the front of the car, and greater downforce created by that upgraded front fascia, combined with the effects of the rear diffuser would create a much more solid car at high speed. obviously diffusers and other body pieces were designed to work together, not seperately. If we can atleast agree on that, then I think we can we can both walk away from this thread peacefully haha, good show!

 

lol good point!

 

I have an older R E Amemiya rear diffuser.

I got it because I think it is esthetically more pleasing than the stock plastic rear piece.

Concernings the functionality of my diffuser or any other R E Amemiya diffuser, I think that it does **** other than collect little pebbles. One day, the collection of pebbles and debris will be placed in a time capsule so that future generations can see where I have travelled in my antiquated gas guzzling machine.

Unless I have my own ocular proof that the diffuser is tested in a wind tunnel, I will neither believe your(StokedXIV's) or R E Amemiya's claim that the diffuser does anything else.

 

effective or not either way most diffusers look like plows for your fields...

 

This is a very good post to read for knowing more aerodynamic stuff!

 

First off downforce always causes drag; you never, ever get something for nothing. The most perfet aero shape in the world would have no drag and thus be incapable of producing lift or downforce. Some aero devices are more efficient and thus produce downforce with less drag (a venturi vs. a spoiler for instance) but there is ALWAYS drag when you make downforce. Downforce is created by taking energy from the oncoming air and using its forces to work for you. That energy is turned into drag on the car; Conservation of Energy still applies.

Drag of course lowers the top speed of the vehicle and every racecar engineer understands this. The gain with downforce is not outright speed, it's grip in the corners. The increased downforce lets the car corner at higher speed yet leaves it slower in acceleration off of them and down the straights because of the increased drag. This is the big game everyone plays at the tracks and why you hear of one guy running a high downforce setup (favors speed in turns) and one guy running a low downforce setup (favors speed on straights). Even though the car with downforce is slower down the straight and off the corners it makes up for that by being much faster through the corners, thus its overall laptime is faster.

Here's a great example from Indianapolis in 1971 and 1972. In '72 Indy allowed bigger wings and so the cars took advantage of this. Even though their straightaway speeds were lower their cornering speeds were much higher. If you come out of the corner already going "fast" you don't need to accelerate the car as much while going down the straight.

Pole speed in 1971 was Mark Donahue who carried 163 mph in the turns and topped out on the straights at 217 mph for a 179 mph average speed. In 1972 with bigger wings Bobby Unser carried 183 mph in the turns and only 206 mph down the straights for an average speed of 196 mph. This is a perfect example of how downforce increases drag on the car and yet laptime plummets. The engine doesn't like pushing the extra load but the tires love the extra grip. Tires and grip will always outrun engines.

 

I almost bought the older style RE-A on nopiston GB a few months ago. Purely for aesthetic reason to balance out the rear spoiler, not aerodynamics. But I had a chance to look at a car that had it on for a few years. Yikes, the thing looks battered from all the rock chip.

 

I agree with what you wrote.
However, you failed to address issue of the amount of drag that a diffuser induces in comparison to a rear wing.
For the same of amount of downforce generated, a diffuser will be more "efficient" than a rear wing in that it will cause much less drag.

 

I did? Read it again

 

Sorry. My bad. I guess I skimmed over it.

 

i like the diffuser,

 

Can you post a pic... I'm interested as to the extent of damage.
I'm trying to find a paint compound that is somewhat rubberized, so that it matches the matte look of the stocker / R1 front Lip, and reduces rock chip damage.

 

I'm in the same boat...I'm assuming you got in on the GB at the other forum.

I think the perfect coating would be durable, high-temp resistant, have a black matte look, and have no problems sticking to the black gel coat. If anybody has a suggestion other than Rino-lining, let us know.

 

A bit of searching on the net has yeilded this...
According to manufacturer it sticks to fiberglass



http://www.pickupspecialties.com/Her...n_bedliner.htm

(re: GB) Yes barely, made it... had to twist chucks arm

I also found this, but it's more of a service, the guy on the phone quoted me $150
for the area I was talking about.. so $50 more than the do it yourself kit...

http://www.goline-x.com/

 

Weird, Rhino Liner Quoted me $300
XLiner Quoted me $150
And the paint is $100

Anybody have any experience with any of these on a truck !?

 

I was reading somewhere that the reason why Ferrari elected to go sans rear wing and with a diffuser instead is that the diffuser has NO drag.

Now, is that true?

 

No. It has LESS drag than a wing but still produces drag. Nothing is ever free.

 

Don't trip over it.......

 

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Holy mackerel. That is fugly!! REminds me of these freak show where a guy has an appendage like 10 times bigger than normal.

Freaky.

 

It reminds me of what happens to a girls bottom end after a rough night of IN-DA-BUTT!

 

hahaha