so-mars

ahhh finally a pic of the entire thing this makes elucidation much easier

so im guessing here based on my visualization of air flow... but having a rear spoiler would be counter productive with a diffuser non? because you'd be creating a vacuum between the spoiler and diffuser meaning it'd slow the car down or something equally non-effective ?

Juiceh

iTrader: (4)

I dunno about counter productive. Diffusers don't really do much until you get up to high speeds. A functional spoiler would probably provide more downforce at lower speeds than a diffuser. A spoiler could actually even help by providing downforce earlier at lower speeds and pressing the rear end closer to the ground allowing the diffuser to work better and keeping it low at high speeds too.

By lower speeds I mean like 50-60MPH and by higher speeds I mean like 90-100+

You would have more drag and extra weight so thats gonna slow you down a tad. But just bump the boost 1-2psi or so.

Black91n/a

http://www.fatcatmotorsports.com/chassis.htm

Go there, click on the link at the bottom, in there are articles that explain diffusers, smooth underbodies and so on.

fcunderwater

and already (with all of these different explainations) I've changed my mind about a diffuser...Plus I doubt I'd get any use from it see as how I never really go over 75.

yusoslo

Juiceh.......THANK YOU, being being another intelligent rx-7 owner and backing up my first post. No offense to anyone else. I just dont like missinformed info. I took automotive aerodynamics classes for 2 years adn worked in a wind tunnel. but......I STILL GOOGLED my information before I posted to verify my post was 100% correct.

I thought it was common sense that turbulant air would build up pressure under the cars chassis...you wanna get that **** out of there ASAP.

IF you guys want we can discuss the Venturi principles and also how the addition of the car exhaust into the diffuser can aid in downforce, but if often outlawed in most sanctioned racing events.


Moral of the story......research before ya post.

Anubis06

dammit...this should be the moral of any damn post!

86gxl_fc

just a quick question.. if it was made for non-drafting. what if a motorcyclist was behind you? wouldnt it cause a negative effect on him/her?? i dont really think it'd be safe for on-the-street use seein as MANY motorcyclists are pretty much noobs!.. lol, just a thought.

Anubis06

who gives a ****? he shouldnt be tailgating an rx7 in the first place. either way, itll be our air or our flames shooting of our exhaust pipes

RETed

+1

So how many of you travel at this kinda speeds to take advantage of the effect?


-Ted

86gxl_fc

well the thing is that they dont have to tailgate to get the effects.
just with the blow-by wind can throw a biker off... reason i'm saying is because i'm getting a motorcycle in the near future, and i'd hate to be knocked off but turbulant winds.. especially if i'm riding on the freeway, with moderate winds..

yusoslo

Well TED you are right 99% of the drivers are daily ones. Mine is a SCCA track car. I hate big wings, and I cant find a removable style wing so I want to see how the diffuser helps stability when I am at fully threashold breaking at 155 on the front straight. Aslo I may run canards. At these speeds I think it is pretty important.

But I must agree they look bad *** and I would want one on my street car as well.

Anubis06

they really do look badass

Juiceh

iTrader: (4)

I also agree that diffusers look badass. I have them for my FC and FD, neither are installed yet though.


As for the biker thing and following us too close, I think the exhaust fumes are a bit more to worry about than wind turbulance. Anyone else recall RRTEC's story about getting tailgated by a motorcycle while his vert was untuned? The biker wiped out and claimed that the fumes irritated his eyes and caused him to crash. LOL

Well a few days ago I was driving around my untuned catless 500R vert on the highway and a motorcycle got behind me at one point. Well let me tell you, he dropped back FAST!!! All I could think of was that story as it was happening and I couldn't stop laughing. I was sorta hoping this guy would wipe out too but it didn't happen.

Valkyrie

If you want better handling, you could just take all the money you WOULD be spending on aero parts and buy a used racing kart...hahaha

so-mars

you are sick. go seek help immediately.

DarkKnightFC

From Wikipedia:

Diffuser (automotive)
From Wikipedia, the free encyclopedia
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Bottom: Bottom-view. Top: Side-cut-view, the red circles mark the front and rear diffuser respectivelyA diffuser, in an automotive context, is usually a shaped section of the car underbody which improves the car's aerodynamic properties by enhancing the transition between the high-velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere. It works by providing a space for the underbody airflow to decelerate and expand so that the boundary between the car's airflow and "external" airflow is less turbulent, and it also provides a degree of "wake infill" (the wake being a turbulent area of low pressure that is caused by the passage of the vehicle through the air; this can cause pressure drag).

As the air enters towards the front of the car it accelerates and reduces pressure. There is a second suction peak at the transition of the flat bottom and diffuser. The diffuser then eases this "high velocity" air back to normal velocity and also helps fill in the area behind the race car making the whole underbody a more efficient downforce producing device by reducing drag on the car and increasing downforce.
The aft part of a car underbody can be a diffuser. It tries to connect the underbody to the back without producing turbulences so that Bernoulli's principle applies and the pressure increases while the velocity decreases. The side and the roof end in a sharp edge, so that their pressure does not increase. Because the pressure in the back tends to equilibrate, the pressure below the car is lower than on the side and the roof of the car.

Note that the front of the car slows down the air without a diffuser making this the ideal place for an inlet. But a diffuser reduces the pressure in front of the car and thereby the amount of air pressed below the car. Sometimes a diffuser is used to let the wheel-casing also pump down the pressure below the car. Many small engine-exhausts in the back also help pumping. The exhaust from the engine compartment in the underbody can blows the air outwards by means of convergent nozzles, which reduce the pressure from the high pressure in the compartment to the low pressure below the car (the nozzle is the inverse of the diffuser).

Just clarifying what I said.

Chris

fcunderwater

You can never trust anything on wikipedia! haha jkjk...What that says makes a lot more sense then anything anyone else has said.

RB_eater

iTrader: (1)

He basicaly said the same thing then Juiceh, higher speed lower pressure, that is the Bernouilli principle.