BlackTopKing

iTrader: (1)

Yeah, I think it'll be cool and am strongly encouraging others to do this. I been on and off on mine and will post pics just for show/example but mine is more to fit the body stylings then just downward fins.

My only question is mounting+/gas tank?
I don't see how that is working.
I'm going to put in a strap (flat stock). Something thatll come down and across to mount the diffuser too.

But the rear exhaust....if your not running dumps. I like to see if how others incorporated the tailpipes in.
Other then wider space.

1991sleeper

iTrader: (-3)

What is a diffuser ?

BlackTopKing

iTrader: (1)

It basically channels air that would normally travel under and around the car, filling pockets and creating drag such as wheel wells and rear of chassis.
The diffuser simply diffuses the air and changes the flow under the car to allow the car to have less drag at high speeds.

Put your hand out the window at 60+ and you'll feel drag, shape your hand and you'll feels less.
Some cars use the same idea up front to channel air into intakes, inter coolers or breaks for cooling.

Simple yet effective.

You'll see it used heavy on time attack, NASCAR or top speedsters to help areo.

paul_huryk

The only way a diffuser will work correctly and efficiently would be to relocate the muffler from the stock location to the rear of the car - which would mean cutting the storage well out, fabricating a new floor and putting the muffler right up in that space.

Then you can put aerodynamic pieces on the axles tubes, still have articulation, and have the muffler out of the air stream. It would also allow for a larger diffuser (height), which would help 2x as much as a cobbled one with stock location muffler.

83 Crossfire TA

iTrader: (2)

I could make lots of comments here, but lets start with if you've already built it and tested it, then why do you need to find a body to build it and test it?

RaverRacerX

considering the rear diff would need to be covered.. it sort of makes the mufflers position moot.

all that needs to be done is to get the air out from under the car. you could use a small network of square tubes placed in strategic places to do the job. of course, you would have to trumpet them at the exit to aid expansion/velocity. This picture shows the F1 double diffuser but the concept is the same.



..oi.. i wish i had the money to try all this.. id be up to my knees in CF.

and.. of course as ive said earlier.. you could in theory.. fairly easily build a poor mans blown diffuser,

dennisschreuer

iTrader: (3)

Hi Guys.
I'm already looking at a APR GT250 type wing, doing a splitter, I would be interested in a diffuser, I know we are working off vacuum here, I do not have any exhaust at the rear of the car , so I'm wide open for one, now...LOL
It's esat for me to throw done 200-400 if it looks decent, If I get the splitter done right, this would be nice.
Dennis

RaverRacerX

this thread was more of a thought exercise that petered out. a usable diffuser can be made. its just that no one really has.

CatmanFS

I built one of these things and it worked, amazingly. I posted here and got some really harsh criticism from people, and that's why this sits like this. If you want I can get you a diagram to show how I did it. Mine was on a 4th gen, but I checked the bolt patterns are the same and the original design would still work, although you might want to make it a bit wider.

RaverRacerX

how far back did your diffuser go?

CatmanFS

About 6 inches from the back bumper.

RaverRacerX

thats an accent piece, not a diffuser. a 3rd gen diffuser should extend at least to the PHB.

CatmanFS

What is PHB? It depends on how much side to side drag you're looking for, remember I built one for the 95, so you're probably right, I haven't had a chance to mount one up to a third gen, somebody tboned me before I could get that chance.

But you're probably right, on a third gen with the back bumper being so squared off, you could get away with pulling it back as far as to there with little to no visual cues as to it's existence. The one I made was meant to be kind of subtle. I'm not sure if you're looking for something that could work in a DD kind of situation, or more like a drag strip. Please, elaborate.

RaverRacerX

Panhard bar.

the entire goal of a diffuser is to get air to exit from under teh car as fast as possible. the vains/fences themselves are to separate, straighten, and prevent (mitigate) airflow turbulence. simply getting the air out from under teh car will help but it has to reach far enough back.

CatmanFS

The little fins ended about 6 inches before the bottom end rear, but the flat panel that they mount to went all the way to the back bumper and formed a smooth surface.

I know what you're saying about getting the air to exit quickly, but the point of what I developed was more about eliminating turbulence exiting the rear, as the space where the muffler sits is full of places where air can pocket and drag, and reducing end play for the back of the vehicle. It did both of these things greatly.

Now, if you're looking to make air leave decompress and exit faster, I'm sure some form of abs molding would be mandatory, as the rigid design of the part I created didn't allow for the smooth curves and such as the pic you posted above. Honestly though, I was satisfied with what I had, it reduced turbulence so much, that if felt like a different car, the handling was spectacular.

As far as actual racing, or speed type goals I wouldn't recommend it because you're losing some drag on on the rear end, and adding weight, and it could cause the back end to slip out from under you. One plus side to this is that if your fins are long enough, they can create some significant side to side drag that could assist in this scenario.

The vehicle I designed the for was lost due to another mechanical failure, bent tie rod, and the accident nearly cost me my life. I spun around and did a complete 360 before hitting a guard rail and ending up in a ditch. One could say that some extra side to side friction slowed the vehicle down enough to make it a survivable crash.

Not entirely sure, that's why I posted this, to get you guy's opinion, and I greatly appreciate the interest in the subject, and in the future would be interested in some design theory or construction techniques using abs or some other suitable material that could be fashioned from a solid piece instead of multiple different materials.

InfernalVortex

iTrader: (4)

I've often mulled over some sort of belly pan arrangement. You'd ahve to control the air going under the car, keep it flowing under the car, and then tune the diffuser to that. Otherwise I dont think it's going to accomplish much.

That said... when you say it was a way to keep air from getting "caught" under the bumper... that makes a lot of sense. Could you actually tell a difference?

my idea is something like this... but you'd have to continue it under the car... cover up as much of the underbelly of the car as possible.



And then you'd have to make sure that you direct the air out from under the car in the back in a way that there is more volume in the "diffuser" than there is under the front splitter. This wont create a ton of ground fx downforce or anything, but it will smooth the airflow around the car and prevent lift.

CatmanFS

I noticed a significant difference, just with the diffuser alone.

RaverRacerX

eliminating turbulence is simply part of the equation. the straighter and less turbulent it is... the faster it will travel.

also... you dont want drag... the entire point of a diffuser is down force without the drag penalty..

CatmanFS

Only in racing scenarios. Drag is an essential factor in the aerodynamic balance of the car. A sort of passive speed governor. Regular driving applications could benefit from something as simple as a turbulence reduction system, but to completely eliminate drag could cause unsavory side effects in handling and stability, especially under windy or adverse weather/driving scenarios.

RaverRacerX

no..

this is like the 'you want some back pressure' myth. back pressure is bad just as drag is bad. with exhaust, you want high exhaust velocity. with aero, you want no drag.

by creating a flat bottom, you get rid of massive pockets where the airflow can accumulate. this results in major drag reduction and the actual goal of a flat bottom and diffuser: lift reduction and even creation of down force.

aero balance of a car relies on having the right ratio of down force front to back, not drag.


say it with me: drag is bad.

CatmanFS

I understand what you're saying, but I still believe that proper balance in terms of drag and weight effect a car's handing. why would they design cars like that in the first place? Why doesn't every car have flat bottoms and pure aero design? The answer is that these are features of a racecar, not a regular commuter automobile. I would agree with you because of my experience you want to eliminate all things that would increase resistance moving forward, but you can't say that drag is entirely bad, as no drag is essentially like a slick of butter sliding across a hot pan. You never know which direction it's going to go, and your average driver isn't anticipating this kind of effect. It can lead to dangerous situations. So, for argument's sake, let me say that drag, when used properly, can positively effect a car's aerodynamic properties.

I don't want to argue with you about this, it's more about opinion anyway.

Formula 305

Drag is bad, always, end of story, but all those aero bits are expensive and not necessary for normal street duty. Like the reasoning behind many decisions made by auto companies, they did it to save money where they could.

CatmanFS

They seem happy to me.

Formula 305

This thread is a train wreck! I was intrigued by your idea when you started this thread over a year ago, but the more you post you've proven your understanding of Aero and fluid dynamics is loose at best.

And after 15 months you still have nothing to show with this project. Where is the prototype? Or at least some sort of justification this thing would actually be worth the time & effort to build.

And now you're spamming your own thread with stupid pictures? Stop wasting everybody's time.

willexoIX

"Never know which direction its going to go."

To me it sounds like you have an understanding of aerodynamics but completely forgot that the tires give you traction... And for what its worth hot butter in a pan is a horrible choice of comparison.

Put it this way, a full belly pan with associated splitter and diffuser would generate downforce, therefore increasing traction. So what you are trying to say is that a full belly pan would cause lift and completely negate the traction of the tires?

Just calling it for what it is.

Besides, if what you are saying is true, there would be WAY more wrecks in Nascar and F1.

Edit- And to add, the reason that belly pans and such dont exist in passenger vehicles is simple. Cost. Thats why exotic cars mostly have them, look at the prices. Besides, cars way back when got excellent fuel mileage. Ever wonder why todays cars have less fuel mileage? Oil companies can't make more money, why do you think electric cars had such a hard time getting off the ground?

Well now I am just talking conspiracy theories, lol. So without further ado, I'm out!

RaverRacerX

:facepalm: MANY new sport sedans on up have flat bottoms. even econoboxes are starting to go that direction. drag. is. bad. period, end of story.

if you are having an unstable condition after putting on a diffuser... it is poorly designed and you are creating even more lift.

CatmanFS

Well you all aren't very much fun.

Anyway, I'm just saying that nascar and those types of races are done in controlled environments and in good conditions, not the type of conditions that everyday drivers experience. generally the back end of the third gens is so long and boxy, it makes it... difficult to really put much of anything under there because when you take a steep driveway or something like that, you'll scrape it off the bottom. Your clearance would be whatever you want, but if you were looking at more than just a couple inches it could be a problem, unless you decided to raise the back end, through either lift kits, or in my situation, putting 15" wheels on the front and 16" on the back. Helped a little.

As far as the topic is concerned I think it's doing quite well, I'll post something of questionable legitimacy and the experts here will straighten it out, the entire point of posting in the first place!

I would agree that drag is bad, hands down, blah blah blah. I've spent many hours coasting along on fumes to know the importance of putting every bit of the aerodynamic properties of the car to good use. The issue here is that I'm not sure that your average driver is looking for a full body pan, and those cars you're talking about with the new-age sleek shape flat bottom pans can get tossed around in the wind on highways like grocery bags.

Back to the results I experienced. The down-force was enough to create more traction, and better handling, also the weight of the object seemed to be just right in this area. When you reduce the turbulence of the air leaving the back of the vehicle you get much more stability, as opposed to stock design where the air is getting trapped in front of the back bumper and behind the muffler.

Crosswind resistance was also reduced dramatically. It seemed to be more stable in situations where wind was trying to run from side to side under the vehicle in high wind type scenarios.

btw, I told you I don't have a camaro any more so it makes it kind of hard to build parts for one. Good news is I found a body nearby and I'll prolly have it by the end of the week if I'm lucky, so stick with me guys. I know it sounds like a bunch of BS but I built this and I trust in my work.


ps, one stray pic doesn't derail the thread. Bad attitudes and bickering know it alls tend to do the trick quite well though.

Dakota W.

The amount of irony in this post is simply hilarious.

CatmanFS

Make fun of me. Go ahead. I built it with my own hands, bled on the thing, cried tears of joy seeing it work as well as it did, feeling like I had done something right. So, go ahead post your comments and such. They're funny.

InfernalVortex

iTrader: (4)

No they are LESS likely to be tossed around by wind if they have less drag.

I wonder if this is just due to streamlining turbulence behind the car. generally diffusers are about managing air under the car, not streamlining air behind it. I dont think what you've made is really a diffuser so much as a way to reduce turbulence under the back of the car.

CatmanFS

1. No idea, you probably know more about that than I do.

2. Yes, that was the point, without all the extra baffling it handled and drover better.

padak

iTrader: (10)

Just post a pic of the one you built and tested on the 4th gen. It would end most of the bickering. Also, if you are worried about someone copying your idea from a picture, but what would stop someone if they bought it, to then make 100 and sell them? Doesn't hold water, let alone air

CatmanFS

This is pointless. I'll continue working on it, I'm getting a chassis. I'll have a mock up soon. You can PM me for details.

8Mike9

kinda been following this thread, but have some serious concerns here, as I think many others may as well.

If you are just getting a chassis, then all you are doing is making a part that fits.

What would be you plan to test the actual item?

You can't base what you did on a 4th gen, to a 3rd gen...or all underbodies created equal?

CatmanFS

How inept do you think I am? Of course I'm going to put a motor in it. I want my third gen back. You guys act like you're the only person who likes their cars and I'm just some snake oil salesman trying to rip you off. You couldn't be further from the truth.

Formula 305

You've been working on getting a car for over a year now.... I think we've all lost faith that this is ever going to actually go anywhere. What ever happened to the guy that you knew selling one for $300 last June?

You've shown no progress at all in 16 months, so why wouldn't we all be skeptical?

CatmanFS

He died. His children scrapped all the car bodies he had, I learned this within the past 6 months. I know you guys are concerned, as am I, but I'm not going to scrap the whole project whenever a few obstacles pop up. Besides, these cars are becoming classics, if you've already come this far, what would stop you now?

8Mike9

I never made mention of your abilities what so ever.

From your post of finding/looking for a "shell" to build your diffuser, you never mentioned "putting a motor" in it.


Lighten up.

CatmanFS

You all aren't giving me much to work with. I tried being lighthearted, but that didn't work.

BlackTopKing

iTrader: (1)

Wow, so this thread just looped in a huge circle and most of it is challenging the wind tunnel mathematics when none of us even have a diffuser and with the few applied to a thirdgen, who is going at those speeds where it even mattered?!

i mean seriously as i stated months ago and claimed to do a year ago on my build thread, have a diffuser (glass work is done) but i dont care if its actually full filling the 160mph design at 75mph on the high way...


because if that was the case, everyone need to take their spoilers off cause i have never seen documentation (other the MSE wail tail design- which is close to TA wrap around spoilers) of GM testing and concluding effective impact.

I am still really wanting to see someone do this too, why not. On the street it would be a look (just like style of rim and stance) then an aero effective mod.

Simply because the whole under carriage design of a thirdgen would completely kill aero, F1 car designs or any true time attack cars...The Japan Camaro on the second page is an example of how far you would have to go to create this function and even then, again usage? Unless you just lucky enough to live in NV with some dessert road!

so why do this threads always turn like this?....1 person says they are going try something and 10 ppl want wind tunnel products.

So as words of encouragement, dare to be different and dare to try to do something, you want a diffuser. make one...or get the universal off ebay and create something off of that...

just be realistic in your expected goals and others support.

now someone else build this! and if you have...post it!

CatmanFS

That really helps man. Like I said, I've built this before, checked the bolt pattern, the same basic design would work on a third gen. I see what you're saying about the effect only being truly noticeable at high speeds, but if your area is like mine, people already go 20mph over the limit on the reg.

I noticed that at these speeds, 70-90mph the baffling effect was negatively effecting handing as far as the rear end was concerned, where steering and direction of the wheels is out of your control. Air was getting trapped between the rear bumper and muffler and generating undesirable and noticeable turbulence.

My design was able to neutralize this effect and allowed the modest rear spoiler to do it's job correctly. I have the parts I need to build a mock up, a motor I'm rebuilding, and a chassis on the way, which is an 85 with a full size spoiler, not the little lip thing that I had on my old 92. It will be very interesting to test and observe the different results, even at modest speeds.

8Mike9

I'm curious, as to what long term effects could occur if the muffler is shrouded, as the heat will rise to the rear hatch area?...or are you taking this into account as well?

IROCgiraffe

iTrader: (3)

Move muffler elsewhere

InfernalVortex

iTrader: (4)

I would assume you'd louver the bellypan or diffuser in a way that allows some air to pass into/through it but you would control the amount.

This is what is on the bottom of 80s MR2's.



This is two of them... there's only one on each car. But they basically cover what would be the transmission tunnel, which has a lot of coolant lines and so forth running through it.

T/Aperformance

If the design of the rear diffuser was designed right You would move your single muffler put a Y pipe there and run two straight mufflers where the tail pipes are.
Kind of like in the pic here, And one like this would look cool on your cars. And a properly designed rear diffuser will reduce drag and that will help with performance
and increase fuel mileage, mostly high way mileage but not by much.

padak

iTrader: (10)

Wow I love it.. I want!!

Cadaver_Puncher

Ok so I read thru three pages of , " I've done this, it's done that , I have a degree in this, my dick is bigger than yours, my girlfriend's ***** are bigger than your girlfriend's. "...whatever.
What I haven't seen is and pics.
Would it look cool? Possibly
Would it work? Maybe

Pics or it didn't happen

CatmanFS

You're on.

dennisschreuer

iTrader: (3)

Building mine now.
I started off with a pan size 45" wide x 30"depth.
The end closest to the PHB has 30 degree bend up so it doesnt catch any air.
I am using 2 stand offs towards the rear end to hold pan in the front, and the bumper for the rear.
I have made the standoffs 6.5" long out of 1" T6061 aluminum solid roundstock, drilled and tapped in both ends.
I am using the exhaust hangar holes in the frame since the holes are already threaded to mount the standoffs. No rear exhaust to contend with. Once I get that mounted next week, Ill take a look at winglets for the sides, and I will re-visit the diffuser fins (4 to 6) to see if the existing one are levels with the body and tall enough. I am estimating 2 to 3 weeks to complete. I'll take blow by blow pics.
Dennis

8Mike9

Funny how things happen...had never heard of a diffuser, until this thread...then low and behold today, heading back from town, I see a newer Mustang....with a diffuser!

Other than this thread, never seen one before.